From 391ea9d3390ab8bf71984d09cd1bb575f3a98bde Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Mon, 1 May 2023 22:41:24 +0800
Subject: [PATCH 01/27] wip

---
 bsp/src/mill/bsp/BSP.scala                    |   2 +-
 bsp/worker/src/mill/bsp/worker/Utils.scala    |   2 +-
 example/basic/1-simple-scala/build.sc         | 125 +-----------------
 main/api/src/mill/api/Result.scala            |  17 ++-
 main/eval/src/mill/eval/Evaluator.scala       |   8 +-
 main/src/mill/main/MainModule.scala           |  31 ++++-
 main/src/mill/main/RootModule.scala           |  21 +--
 main/src/mill/main/RunScript.scala            |  27 ++--
 main/src/mill/main/VisualizeModule.scala      |   2 +-
 main/src/mill/modules/CoursierSupport.scala   |   9 +-
 main/test/src/mill/main/MainModuleTests.scala |  12 +-
 .../src/mill/util}/Watchable.scala            |   6 +-
 main/util/src/mill/util/Watched.scala         |   6 +-
 .../src/mill/runner/MillBuildBootstrap.scala  |  13 +-
 runner/src/mill/runner/RunnerState.scala      |   3 +-
 runner/src/mill/runner/Watching.scala         |   3 +-
 scalalib/src/mill/scalalib/GenIdeaImpl.scala  |   2 +-
 .../src/mill/scalalib/ResolveDepsTests.scala  |  12 +-
 18 files changed, 111 insertions(+), 190 deletions(-)
 rename main/{define/src/mill/define => util/src/mill/util}/Watchable.scala (80%)

diff --git a/bsp/src/mill/bsp/BSP.scala b/bsp/src/mill/bsp/BSP.scala
index cdac63920e3..e295b75204b 100644
--- a/bsp/src/mill/bsp/BSP.scala
+++ b/bsp/src/mill/bsp/BSP.scala
@@ -96,7 +96,7 @@ object BSP extends ExternalModule with CoursierModule with BspServerStarter {
     val worker = BspWorker(ctx)
 
     worker match {
-      case Result.Success(worker) =>
+      case Result.Success(worker, _) =>
         worker.startBspServer(
           initialEvaluator,
           streams,
diff --git a/bsp/worker/src/mill/bsp/worker/Utils.scala b/bsp/worker/src/mill/bsp/worker/Utils.scala
index dba6b0faeef..64c54cc0fe6 100644
--- a/bsp/worker/src/mill/bsp/worker/Utils.scala
+++ b/bsp/worker/src/mill/bsp/worker/Utils.scala
@@ -46,7 +46,7 @@ object Utils {
       task: mill.define.Task[_]
   ): StatusCode = {
     results.results(task) match {
-      case Success(_) => StatusCode.OK
+      case Success(_, _) => StatusCode.OK
       case Skipped => StatusCode.CANCELLED
       case _ => StatusCode.ERROR
     }
diff --git a/example/basic/1-simple-scala/build.sc b/example/basic/1-simple-scala/build.sc
index 3be43e9ade7..a24fd0f20c8 100644
--- a/example/basic/1-simple-scala/build.sc
+++ b/example/basic/1-simple-scala/build.sc
@@ -1,124 +1,9 @@
 
-import mill._, scalalib._
+import mill._
 
-object foo extends RootModule with ScalaModule {
-  def scalaVersion = "2.13.8"
-  def ivyDeps = Agg(
-    ivy"com.lihaoyi::scalatags:0.8.2",
-    ivy"com.lihaoyi::mainargs:0.4.0"
-  )
+//interp.watchValue(System.currentTimeMillis() / 1000)
 
-  object test extends Tests {
-    def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.7.11")
-    def testFramework = "utest.runner.Framework"
-  }
-}
+println("Setting up build.sc")
+def foo = T.input{ System.currentTimeMillis() / 1000 }
 
-// This is a basic Mill build for a single `ScalaModule`, with two
-// third-party dependencies and a test suite using the uTest framework. As a
-// single-module project, it `extends RootModule` to mark `object foo` as the
-// top-level module in the build. This lets us directly perform operations
-// `./mill compile` or `./mill run` without needing to prefix it as
-// `foo.compile` or `foo.run`.
-//
-// You can download this example project using the *download* link above
-// if you want to try out the commands below yourself. The only requirement is
-// that you have some version of the JVM installed; the `./mill` script takes
-// care of any further dependencies that need to be downloaded.
-//
-// The source code for this module lives in the `src/` folder.
-// Output for this module (compiled files, resolved dependency lists, ...)
-// lives in `out/`.
-//
-// This example project uses two third-party dependencies - MainArgs for CLI
-// argument parsing, Scalatags for HTML generation - and uses them to wrap a
-// given input string in HTML templates with proper escaping.
-//
-// You can run `assembly` to generate a standalone executable jar, which then
-// can be run from the command line or deployed to be run elsewhere.
-
-/** Usage
-
-> ./mill resolve _ # List what tasks are available to run
-assembly
-...
-clean
-...
-compile
-...
-run
-...
-show
-...
-inspect
-...
-
-> ./mill inspect compile # Show documentation and inputs of a task
-compile(ScalaModule.scala:...)
-    Compiles the current module to generate compiled classfiles/bytecode.
-Inputs:
-    scalaVersion
-    upstreamCompileOutput
-    allSourceFiles
-    compileClasspath
-
-> ./mill compile # compile sources into classfiles
-...
-compiling 1 Scala source to...
-
-> ./mill run # run the main method, if any
-error: Missing argument: --text <str>
-
-> ./mill run --text hello
-<h1>hello</h1>
-
-> ./mill test
-...
-+ foo.FooTests.simple ...  <h1>hello</h1>
-+ foo.FooTests.escaping ...  <h1>&lt;hello&gt;</h1>
-
-> ./mill assembly # bundle classfiles and libraries into a jar for deployment
-
-> ./mill show assembly # show the output of the assembly task
-".../out/assembly.dest/out.jar"
-
-> java -jar ./out/assembly.dest/out.jar --text hello
-<h1>hello</h1>
-
-> ./out/assembly.dest/out.jar --text hello # mac/linux
-<h1>hello</h1>
-
-*/
-
-// The output of every Mill task is stored in the `out/` folder under a name
-// corresponding to the task that created it. e.g. The `assembly` task puts its
-// metadata output in `out/assembly.json`, and its output files in
-// `out/assembly.dest`. You can also use `show` to make Mill print out the
-// metadata output for a particular task.
-//
-// Additional Mill tasks you would likely need include:
-//
-// [source,bash]
-// ----
-// $ mill runBackground # run the main method in the background
-//
-// $ mill clean <task>  # delete the cached output of a task, terminate any runBackground
-//
-// $ mill launcher      # prepares a foo/launcher.dest/run you can run later
-//
-// $ mill jar           # bundle the classfiles into a jar suitable for publishing
-//
-// $ mill -i console    # start a Scala console within your project
-//
-// $ mill -i repl       # start an Ammonite Scala REPL within your project
-// ----
-//
-// You can run `+mill resolve __+` to see a full list of the different tasks that
-// are available, `+mill resolve _+` to see the tasks within `foo`,
-// `mill inspect compile` to inspect a task's doc-comment documentation or what
-// it depends on, or `mill show foo.scalaVersion` to show the output of any task.
-//
-// The most common *tasks* that Mill can run are cached *targets*, such as
-// `compile`, and un-cached *commands* such as `foo.run`. Targets do not
-// re-evaluate unless one of their inputs changes, whereas commands re-run every
-// time.
\ No newline at end of file
+def bar = T{ foo() + " seconds since the epoch" }
\ No newline at end of file
diff --git a/main/api/src/mill/api/Result.scala b/main/api/src/mill/api/Result.scala
index 5ec9a6e99c3..d5905fcef99 100644
--- a/main/api/src/mill/api/Result.scala
+++ b/main/api/src/mill/api/Result.scala
@@ -27,11 +27,24 @@ object Result {
    * @param value The value computed by the task.
    * @tparam T The result type of the computed task.
    */
-  case class Success[+T](value: T) extends Result[T] {
-    def map[V](f: T => V): Success[V] = Result.Success(f(value))
+  case class Success[+T](value: T, signature: () => Int) extends Result[T] {
+    def map[V](f: T => V): Success[V] = Result.Success(f(value), signature)
     def flatMap[V](f: T => Result[V]): Result[V] = f(value)
     override def asSuccess: Option[Success[T]] = Some(this)
   }
+  object Success{
+    def apply[T](value: => T) = {
+      new Success(
+        value,
+        () => {
+//          if (value.toString.length < 100) {
+//            mill.api.SystemStreams.originalErr.println("Signature " + System.identityHashCode(value))
+//          }
+          value.hashCode()
+        }
+      )
+    }
+  }
 
   /**
    * A task execution was skipped because of failures in it's dependencies.
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 32eeb2a8b3a..bd26d4744a7 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -423,7 +423,7 @@ class Evaluator private (
         upToDateWorker.map((_, inputsHash)) orElse cached match {
           case Some((v, hashCode)) =>
             val newResults = mutable.LinkedHashMap.empty[Task[_], mill.api.Result[(Any, Int)]]
-            newResults(labelledNamedTask.task) = mill.api.Result.Success((v, hashCode))
+            newResults(labelledNamedTask.task) = mill.api.Result.Success((v, hashCode), () => 0)
 
             Evaluated(newResults, Nil, cached = true)
 
@@ -452,7 +452,7 @@ class Evaluator private (
               case mill.api.Result.Failure(_, Some((v, _))) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
-              case mill.api.Result.Success((v, _)) =>
+              case mill.api.Result.Success((v, _), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case _ =>
@@ -557,7 +557,7 @@ class Evaluator private (
       newEvaluated.append(task)
       val targetInputValues = task.inputs
         .map { x => newResults.getOrElse(x, results(x)) }
-        .collect { case mill.api.Result.Success((v, _)) => v }
+        .collect { case mill.api.Result.Success((v, _), _) => v }
 
       val res =
         if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
@@ -771,7 +771,7 @@ object Evaluator {
       failing: MultiBiMap[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]],
       results: collection.Map[Task[_], mill.api.Result[Any]]
   ) {
-    def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v) => v }
+    def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v, _) => v }
     private def copy(
         rawValues: Seq[Result[Any]] = rawValues,
         evaluated: Agg[Task[_]] = evaluated,
diff --git a/main/src/mill/main/MainModule.scala b/main/src/mill/main/MainModule.scala
index c3a54290856..a9948128da7 100644
--- a/main/src/mill/main/MainModule.scala
+++ b/main/src/mill/main/MainModule.scala
@@ -3,9 +3,9 @@ package mill.main
 import java.util.concurrent.LinkedBlockingQueue
 import mill.{BuildInfo, T}
 import mill.api.{Ctx, PathRef, Result, internal}
-import mill.define.{Command, Segments, NamedTask, TargetImpl, Task}
+import mill.define.{Command, NamedTask, Segments, TargetImpl, Task}
 import mill.eval.{Evaluator, EvaluatorPaths}
-import mill.util.{PrintLogger, Watched}
+import mill.util.{PrintLogger, Watchable, Watched}
 import pprint.{Renderer, Tree, Truncated}
 import ujson.Value
 
@@ -60,6 +60,32 @@ object MainModule {
  * [[show]], [[inspect]], [[plan]], etc.
  */
 trait MainModule extends mill.Module {
+  protected[mill] val watchedValues = mutable.Buffer.empty[Watchable]
+
+  object interp {
+
+    def watchValue[T](v0: => T)(implicit fn: sourcecode.FileName, ln: sourcecode.Line): T = {
+      val v = v0
+      val watchable = Watchable.Value(
+        () => v0.hashCode,
+        v.hashCode(),
+        fn.value + ":" + ln.value
+      )
+      watchedValues.append(watchable)
+      v
+    }
+
+    def watch(p: os.Path): os.Path = {
+      val watchable = Watchable.Path(PathRef(p))
+      watchedValues.append(watchable)
+      p
+    }
+
+    def watch0(w: Watchable): Unit = {
+      watchedValues.append(w)
+    }
+  }
+
 
   implicit def millDiscover: mill.define.Discover[_]
 
@@ -265,6 +291,7 @@ trait MainModule extends mill.Module {
       T.log.outputStream.println(output.render(indent = 2))
       output
     }.map { res: Watched[Option[Value]] =>
+      res.watched.foreach(interp.watch0)
       res.value.getOrElse(ujson.Null)
     }
   }
diff --git a/main/src/mill/main/RootModule.scala b/main/src/mill/main/RootModule.scala
index 7c19b0871a4..3ba1bfe54ab 100644
--- a/main/src/mill/main/RootModule.scala
+++ b/main/src/mill/main/RootModule.scala
@@ -1,7 +1,8 @@
 package mill.main
 
 import mill.api.{PathRef, internal}
-import mill.define.{Caller, Discover, Segments, Watchable}
+import mill.util.Watchable
+import mill.define.{Caller, Discover, Segments}
 import TokenReaders._
 
 import scala.collection.mutable
@@ -36,24 +37,6 @@ abstract class RootModule()(implicit
   // user-defined BaseModule can have a complete Discover[_] instance without
   // needing to tediously call `override lazy val millDiscover = Discover[this.type]`
   override lazy val millDiscover = baseModuleInfo.discover.asInstanceOf[Discover[this.type]]
-
-  object interp {
-
-    def watchValue[T](v0: => T): T = {
-      val v = v0
-      val watchable = Watchable.Value(() => v0.hashCode, v.hashCode())
-      watchedValues.append(watchable)
-      v
-    }
-
-    def watch(p: os.Path): os.Path = {
-      val watchable = Watchable.Path(PathRef(p))
-      watchedValues.append(watchable)
-      p
-    }
-  }
-
-  protected[mill] val watchedValues = mutable.Buffer.empty[Watchable]
 }
 
 @internal
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 36227805f89..109c56262d6 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -2,11 +2,10 @@ package mill.main
 
 import mill.define._
 import mill.eval.{Evaluator, EvaluatorPaths}
-import mill.util.{EitherOps, Watched}
+import mill.util.{Watchable, Watched}
 import mill.api.{PathRef, Result}
 import mill.api.Strict.Agg
-import scala.reflect.ClassTag
-import mill.main.ParseArgs.TargetsWithParams
+
 
 object RunScript {
 
@@ -16,7 +15,7 @@ object RunScript {
       evaluator: Evaluator,
       scriptArgs: Seq[String],
       selectMode: SelectMode
-  ): Either[String, (Seq[PathRef], Either[String, Seq[(Any, Option[ujson.Value])]])] = {
+  ): Either[String, (Seq[Watchable], Either[String, Seq[(Any, Option[ujson.Value])]])] = {
     for (targets <- ResolveTasks.resolve(evaluator, scriptArgs, selectMode))
       yield {
         val (watched, res) = evaluate(evaluator, Agg.from(targets.distinct))
@@ -27,6 +26,8 @@ object RunScript {
           w <- extraWatched
         } yield w
 
+        pprint.log(watched.map(_.pretty))
+        pprint.log(watched2.map(_.pretty))
         (watched ++ watched2, res)
       }
   }
@@ -35,7 +36,7 @@ object RunScript {
       evaluator: Evaluator,
       scriptArgs: Seq[String],
       selectMode: SelectMode
-  ): Either[String, (Seq[PathRef], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])] = {
+  ): Either[String, (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])] = {
     for (targets <- ResolveTasks.resolve(evaluator, scriptArgs, selectMode))
       yield {
         val (watched, res) = evaluateNamed(evaluator, Agg.from(targets.distinct))
@@ -53,8 +54,9 @@ object RunScript {
   def evaluate(
       evaluator: Evaluator,
       targets: Agg[Task[Any]]
-  ): (Seq[PathRef], Either[String, Seq[(Any, Option[ujson.Value])]]) = {
+  ): (Seq[Watchable], Either[String, Seq[(Any, Option[ujson.Value])]]) = {
     val (watched, results) = evaluateNamed(evaluator, targets)
+    pprint.log(watched.map(_.pretty))
     // we drop the task name in the inner tuple
     (watched, results.map(_.map(p => (p._1, p._2.map(_._2)))))
   }
@@ -67,17 +69,24 @@ object RunScript {
   def evaluateNamed(
       evaluator: Evaluator,
       targets: Agg[Task[Any]]
-  ): (Seq[PathRef], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]]) = {
+  ): (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]]) = {
     val evaluated: Evaluator.Results = evaluator.evaluate(targets)
     val watched = evaluated.results
       .iterator
       .collect {
-        case (t: SourcesImpl, Result.Success(ps: Seq[PathRef])) => ps
-        case (t: SourceImpl, Result.Success(p: PathRef)) => Seq(p)
+        case (t: SourcesImpl, Result.Success(ps: Seq[PathRef], _)) => ps.map(Watchable.Path(_))
+        case (t: SourceImpl, Result.Success(p: PathRef, _)) => Seq(Watchable.Path(p))
+        case (t: InputImpl[_], Result.Success(v, signature)) =>
+          val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
+          println("INPUT FOUND " + pretty)
+          Seq(Watchable.Value(() => signature(), signature(), pretty))
       }
       .flatten
       .toSeq
 
+    pprint.log(targets)
+    pprint.log(watched.map(_.pretty))
+
     val errorStr = Evaluator.formatFailing(evaluated)
 
     evaluated.failing.keyCount match {
diff --git a/main/src/mill/main/VisualizeModule.scala b/main/src/mill/main/VisualizeModule.scala
index f7ed10b61ee..809835d3513 100644
--- a/main/src/mill/main/VisualizeModule.scala
+++ b/main/src/mill/main/VisualizeModule.scala
@@ -43,7 +43,7 @@ trait VisualizeModule extends mill.define.TaskModule {
     )
     val visualizeThread = new java.lang.Thread(() =>
       while (true) {
-        val res = Result.create {
+        val res = Result.Success{
           val (targets, tasks, dest) = in.take()
           cl.loadClass("mill.main.graphviz.GraphvizTools")
             .getMethod("apply", classOf[Seq[_]], classOf[Seq[_]], classOf[os.Path])
diff --git a/main/src/mill/modules/CoursierSupport.scala b/main/src/mill/modules/CoursierSupport.scala
index b51f2c6f269..707474908b7 100644
--- a/main/src/mill/modules/CoursierSupport.scala
+++ b/main/src/mill/modules/CoursierSupport.scala
@@ -192,10 +192,11 @@ trait CoursierSupport {
       }
 
       if (errors.isEmpty) {
-        mill.Agg.from(
-          successes.map(os.Path(_)).filter(_.ext == "jar").map(PathRef(_, quick = true))
-        ).filter(x => resolveFilter(x.path)) ++ localTestDeps.flatten
-
+        Result.Success(
+          mill.Agg.from(
+            successes.map(os.Path(_)).filter(_.ext == "jar").map(PathRef(_, quick = true))
+          ).filter(x => resolveFilter(x.path)) ++ localTestDeps.flatten
+        )
       } else {
         val errorDetails = errors.map(e => s"${System.lineSeparator()}  ${e.describe}").mkString
         Result.Failure(
diff --git a/main/test/src/mill/main/MainModuleTests.scala b/main/test/src/mill/main/MainModuleTests.scala
index aca9b114add..4572e4247a6 100644
--- a/main/test/src/mill/main/MainModuleTests.scala
+++ b/main/test/src/mill/main/MainModuleTests.scala
@@ -49,7 +49,7 @@ object MainModuleTests extends TestSuite {
       val eval = new TestEvaluator(mainModule)
       test("single") {
         val res = eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello")))
-        val Result.Success(value: String) = res.rawValues.head
+        val Result.Success(value: String, _) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -59,7 +59,7 @@ object MainModuleTests extends TestSuite {
       test("multi") {
         val res =
           eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello", "hello2")))
-        val Result.Success(value: String) = res.rawValues.head
+        val Result.Success(value: String, _) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -77,7 +77,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(value, _) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq("hello", "world")))
       }
@@ -92,7 +92,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(value, _) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq(
           ujson.Arr.from(Seq("hello", "world")),
@@ -109,7 +109,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(value, _) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world"))
@@ -126,7 +126,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(value, _) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world")),
diff --git a/main/define/src/mill/define/Watchable.scala b/main/util/src/mill/util/Watchable.scala
similarity index 80%
rename from main/define/src/mill/define/Watchable.scala
rename to main/util/src/mill/util/Watchable.scala
index 66949e664d8..f465379937e 100644
--- a/main/define/src/mill/define/Watchable.scala
+++ b/main/util/src/mill/util/Watchable.scala
@@ -1,4 +1,4 @@
-package mill.define
+package mill.util
 
 import mill.api.internal
 
@@ -13,14 +13,16 @@ private[mill] trait Watchable {
   def poll(): Long
   def signature: Long
   def validate(): Boolean = poll() == signature
+  def pretty: String
 }
 @internal
 private[mill] object Watchable {
   case class Path(p: mill.api.PathRef) extends Watchable {
     def poll() = p.recomputeSig()
     def signature = p.sig
+    def pretty = p.toString
   }
-  case class Value(f: () => Long, signature: Long) extends Watchable {
+  case class Value(f: () => Long, signature: Long, pretty: String) extends Watchable {
     def poll() = f()
   }
 }
diff --git a/main/util/src/mill/util/Watched.scala b/main/util/src/mill/util/Watched.scala
index 4e7ee66a6ee..93ecc9704a5 100644
--- a/main/util/src/mill/util/Watched.scala
+++ b/main/util/src/mill/util/Watched.scala
@@ -2,8 +2,8 @@ package mill.util
 
 import mill.api.PathRef
 
-case class Watched[T](value: T, watched: Seq[PathRef])
+case class Watched[T](value: T, watched: Seq[Watchable])
 object Watched {
-  implicit def readWrite[T: upickle.default.ReadWriter]: upickle.default.ReadWriter[Watched[T]] =
-    upickle.default.macroRW[Watched[T]]
+//  implicit def readWrite[T: upickle.default.ReadWriter]: upickle.default.ReadWriter[Watched[T]] =
+//    upickle.default.macroRW[Watched[T]]
 }
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index 04b8c5f00af..5af8ba8768b 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -1,11 +1,11 @@
 package mill.runner
-import mill.util.{ColorLogger, PrefixLogger, Util}
+import mill.util.{ColorLogger, PrefixLogger, Util, Watchable}
 import mill.{BuildInfo, T}
 import mill.api.{PathRef, internal}
 import mill.eval.Evaluator
 import mill.main.{RootModule, RunScript, SelectMode}
 import mill.main.TokenReaders._
-import mill.define.{Discover, Segments, Watchable}
+import mill.define.{Discover, Segments}
 
 import java.net.URLClassLoader
 
@@ -48,6 +48,7 @@ class MillBuildBootstrap(
       )
     }
 
+    pprint.log(runnerState.frames.map(_.evalWatched.map(_.pretty)))
     Watching.Result(
       watched = runnerState.frames.flatMap(_.evalWatched),
       error = runnerState.errorOpt,
@@ -254,6 +255,7 @@ class MillBuildBootstrap(
     val (evaled, evalWatched, moduleWatches) =
       MillBuildBootstrap.evaluateWithWatches(rootModule, evaluator, targetsAndParams)
 
+
     val evalState = RunnerState.Frame(
       evaluator.workerCache.toMap,
       evalWatched,
@@ -338,11 +340,10 @@ object MillBuildBootstrap {
 
     evalTaskResult match {
       case Left(msg) => (Left(msg), Nil, moduleWatched)
-      case Right((watchedPaths, evaluated)) =>
-        val evalWatched = watchedPaths.map(Watchable.Path)
+      case Right((watched, evaluated)) =>
         evaluated match {
-          case Left(msg) => (Left(msg), evalWatched, moduleWatched)
-          case Right(results) => (Right(results.map(_._1)), evalWatched, moduleWatched)
+          case Left(msg) => (Left(msg), watched, moduleWatched)
+          case Right(results) => (Right(results.map(_._1)), watched, moduleWatched)
         }
     }
   }
diff --git a/runner/src/mill/runner/RunnerState.scala b/runner/src/mill/runner/RunnerState.scala
index 3c60d76a951..c7b05545661 100644
--- a/runner/src/mill/runner/RunnerState.scala
+++ b/runner/src/mill/runner/RunnerState.scala
@@ -1,7 +1,8 @@
 package mill.runner
 
 import mill.api.{PathRef, internal}
-import mill.define.{BaseModule, Segments, Watchable}
+import mill.define.{BaseModule, Segments}
+import mill.util.Watchable
 import upickle.default.{ReadWriter, macroRW}
 import mill.api.JsonFormatters._
 import mill.main.RootModule
diff --git a/runner/src/mill/runner/Watching.scala b/runner/src/mill/runner/Watching.scala
index a55f21bce62..2e65e36b161 100644
--- a/runner/src/mill/runner/Watching.scala
+++ b/runner/src/mill/runner/Watching.scala
@@ -1,8 +1,7 @@
 package mill.runner
 
 import mill.api.internal
-import mill.define.Watchable
-import mill.util.ColorLogger
+import mill.util.{ColorLogger, Watchable}
 import mill.api.SystemStreams
 import java.io.InputStream
 import scala.annotation.tailrec
diff --git a/scalalib/src/mill/scalalib/GenIdeaImpl.scala b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
index 4f0c97cc613..ae6b46793a5 100755
--- a/scalalib/src/mill/scalalib/GenIdeaImpl.scala
+++ b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
@@ -105,7 +105,7 @@ case class GenIdeaImpl(
             val millDeps = BuildInfo.millEmbeddedDeps.split(",").map(d => ivy"$d").map(dep =>
               BoundDep(Lib.depToDependency(dep, BuildInfo.scalaVersion, ""), dep.force)
             )
-            val Result.Success(res) = scalalib.Lib.resolveDependencies(
+            val Result.Success(res, _) = scalalib.Lib.resolveDependencies(
               repositories = repos.toList,
               deps = millDeps,
               sources = false,
diff --git a/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala b/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
index 3fe25078286..61404c4add5 100644
--- a/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
+++ b/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
@@ -19,20 +19,20 @@ object ResolveDepsTests extends TestSuite {
   val tests = Tests {
     "resolveValidDeps" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3")
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(paths.nonEmpty)
     }
 
     "resolveValidDepsWithClassifier" - {
       val deps = Agg(ivy"org.lwjgl:lwjgl:3.1.1;classifier=natives-macos")
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(paths.nonEmpty)
       assert(paths.items.next().path.toString.contains("natives-macos"))
     }
 
     "resolveTransitiveRuntimeDeps" - {
       val deps = Agg(ivy"org.mockito:mockito-core:2.7.22")
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(paths.nonEmpty)
       assert(paths.exists(_.path.toString.contains("objenesis")))
       assert(paths.exists(_.path.toString.contains("byte-buddy")))
@@ -40,13 +40,13 @@ object ResolveDepsTests extends TestSuite {
 
     "excludeTransitiveDeps" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".exclude("com.lihaoyi" -> "fansi_2.12"))
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(!paths.exists(_.path.toString.contains("fansi_2.12")))
     }
 
     "excludeTransitiveDepsByOrg" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".excludeOrg("com.lihaoyi"))
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(!paths.exists(path =>
         path.path.toString.contains("com/lihaoyi") && !path.path.toString.contains("pprint_2.12")
       ))
@@ -54,7 +54,7 @@ object ResolveDepsTests extends TestSuite {
 
     "excludeTransitiveDepsByName" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".excludeName("fansi_2.12"))
-      val Success(paths) = evalDeps(deps)
+      val Success(paths, _) = evalDeps(deps)
       assert(!paths.exists(_.path.toString.contains("fansi_2.12")))
     }
 

From 020964edcaca65891a9e79f828252a4a43251ed1 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 00:17:44 +0800
Subject: [PATCH 02/27] .

---
 example/basic/1-simple-scala/build.sc         | 125 +++++++++++++++++-
 main/api/src/mill/api/Ctx.scala               |   6 +-
 main/define/src/mill/define/Task.scala        |  12 +-
 main/eval/src/mill/eval/Evaluator.scala       |   4 +-
 main/src/mill/main/RunScript.scala            |   7 -
 .../src/mill/runner/MillBuildBootstrap.scala  |   1 -
 6 files changed, 132 insertions(+), 23 deletions(-)

diff --git a/example/basic/1-simple-scala/build.sc b/example/basic/1-simple-scala/build.sc
index a24fd0f20c8..3be43e9ade7 100644
--- a/example/basic/1-simple-scala/build.sc
+++ b/example/basic/1-simple-scala/build.sc
@@ -1,9 +1,124 @@
 
-import mill._
+import mill._, scalalib._
 
-//interp.watchValue(System.currentTimeMillis() / 1000)
+object foo extends RootModule with ScalaModule {
+  def scalaVersion = "2.13.8"
+  def ivyDeps = Agg(
+    ivy"com.lihaoyi::scalatags:0.8.2",
+    ivy"com.lihaoyi::mainargs:0.4.0"
+  )
 
-println("Setting up build.sc")
-def foo = T.input{ System.currentTimeMillis() / 1000 }
+  object test extends Tests {
+    def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.7.11")
+    def testFramework = "utest.runner.Framework"
+  }
+}
 
-def bar = T{ foo() + " seconds since the epoch" }
\ No newline at end of file
+// This is a basic Mill build for a single `ScalaModule`, with two
+// third-party dependencies and a test suite using the uTest framework. As a
+// single-module project, it `extends RootModule` to mark `object foo` as the
+// top-level module in the build. This lets us directly perform operations
+// `./mill compile` or `./mill run` without needing to prefix it as
+// `foo.compile` or `foo.run`.
+//
+// You can download this example project using the *download* link above
+// if you want to try out the commands below yourself. The only requirement is
+// that you have some version of the JVM installed; the `./mill` script takes
+// care of any further dependencies that need to be downloaded.
+//
+// The source code for this module lives in the `src/` folder.
+// Output for this module (compiled files, resolved dependency lists, ...)
+// lives in `out/`.
+//
+// This example project uses two third-party dependencies - MainArgs for CLI
+// argument parsing, Scalatags for HTML generation - and uses them to wrap a
+// given input string in HTML templates with proper escaping.
+//
+// You can run `assembly` to generate a standalone executable jar, which then
+// can be run from the command line or deployed to be run elsewhere.
+
+/** Usage
+
+> ./mill resolve _ # List what tasks are available to run
+assembly
+...
+clean
+...
+compile
+...
+run
+...
+show
+...
+inspect
+...
+
+> ./mill inspect compile # Show documentation and inputs of a task
+compile(ScalaModule.scala:...)
+    Compiles the current module to generate compiled classfiles/bytecode.
+Inputs:
+    scalaVersion
+    upstreamCompileOutput
+    allSourceFiles
+    compileClasspath
+
+> ./mill compile # compile sources into classfiles
+...
+compiling 1 Scala source to...
+
+> ./mill run # run the main method, if any
+error: Missing argument: --text <str>
+
+> ./mill run --text hello
+<h1>hello</h1>
+
+> ./mill test
+...
++ foo.FooTests.simple ...  <h1>hello</h1>
++ foo.FooTests.escaping ...  <h1>&lt;hello&gt;</h1>
+
+> ./mill assembly # bundle classfiles and libraries into a jar for deployment
+
+> ./mill show assembly # show the output of the assembly task
+".../out/assembly.dest/out.jar"
+
+> java -jar ./out/assembly.dest/out.jar --text hello
+<h1>hello</h1>
+
+> ./out/assembly.dest/out.jar --text hello # mac/linux
+<h1>hello</h1>
+
+*/
+
+// The output of every Mill task is stored in the `out/` folder under a name
+// corresponding to the task that created it. e.g. The `assembly` task puts its
+// metadata output in `out/assembly.json`, and its output files in
+// `out/assembly.dest`. You can also use `show` to make Mill print out the
+// metadata output for a particular task.
+//
+// Additional Mill tasks you would likely need include:
+//
+// [source,bash]
+// ----
+// $ mill runBackground # run the main method in the background
+//
+// $ mill clean <task>  # delete the cached output of a task, terminate any runBackground
+//
+// $ mill launcher      # prepares a foo/launcher.dest/run you can run later
+//
+// $ mill jar           # bundle the classfiles into a jar suitable for publishing
+//
+// $ mill -i console    # start a Scala console within your project
+//
+// $ mill -i repl       # start an Ammonite Scala REPL within your project
+// ----
+//
+// You can run `+mill resolve __+` to see a full list of the different tasks that
+// are available, `+mill resolve _+` to see the tasks within `foo`,
+// `mill inspect compile` to inspect a task's doc-comment documentation or what
+// it depends on, or `mill show foo.scalaVersion` to show the output of any task.
+//
+// The most common *tasks* that Mill can run are cached *targets*, such as
+// `compile`, and un-cached *commands* such as `foo.run`. Targets do not
+// re-evaluate unless one of their inputs changes, whereas commands re-run every
+// time.
\ No newline at end of file
diff --git a/main/api/src/mill/api/Ctx.scala b/main/api/src/mill/api/Ctx.scala
index 8455a9a9c36..c4cc74a22ff 100644
--- a/main/api/src/mill/api/Ctx.scala
+++ b/main/api/src/mill/api/Ctx.scala
@@ -111,7 +111,7 @@ object Ctx {
  * implementation of a `Task`.
  */
 class Ctx(
-    val args: IndexedSeq[_],
+    val args: IndexedSeq[Result.Success[_]],
     dest0: () => os.Path,
     val log: Logger,
     val home: os.Path,
@@ -127,8 +127,8 @@ class Ctx(
     with Ctx.Workspace {
 
   def dest: Path = dest0()
-  def arg[T](index: Int): T = {
-    if (index >= 0 && index < args.length) args(index).asInstanceOf[T]
+  def arg[T](index: Int): Result.Success[T] = {
+    if (index >= 0 && index < args.length) args(index).asInstanceOf[Result.Success[T]]
     else throw new IndexOutOfBoundsException(s"Index $index outside of range 0 - ${args.length}")
   }
 }
diff --git a/main/define/src/mill/define/Task.scala b/main/define/src/mill/define/Task.scala
index 2f5cfdf5881..aa1457ff096 100644
--- a/main/define/src/mill/define/Task.scala
+++ b/main/define/src/mill/define/Task.scala
@@ -58,7 +58,7 @@ object Task {
     val inputs = inputs0
     def evaluate(ctx: mill.api.Ctx) = {
       for (i <- 0 until ctx.args.length)
-        yield ctx.args(i).asInstanceOf[T]
+        yield ctx.arg[T](i).value
     }
   }
   private[define] class TraverseCtx[+T, V](
@@ -69,17 +69,19 @@ object Task {
     def evaluate(ctx: mill.api.Ctx) = {
       f(
         for (i <- 0 until ctx.args.length)
-          yield ctx.args(i).asInstanceOf[T],
+          yield ctx.arg[T](i).value,
         ctx
       )
     }
   }
   private[define] class Mapped[+T, +V](source: Task[T], f: T => V) extends Task[V] {
-    def evaluate(ctx: mill.api.Ctx) = f(ctx.arg(0))
+    def evaluate(ctx: mill.api.Ctx) = ctx.arg(0).map(f)
     val inputs = List(source)
   }
   private[define] class Zipped[+T, +V](source1: Task[T], source2: Task[V]) extends Task[(T, V)] {
-    def evaluate(ctx: mill.api.Ctx) = (ctx.arg(0), ctx.arg(1))
+    def evaluate(ctx: mill.api.Ctx) = (ctx.arg[T](0), ctx.arg[V](1)) match{
+      case (Result.Success(a, _), Result.Success(b, _)) => (a, b)
+    }
     val inputs = List(source1, source2)
   }
 }
@@ -105,7 +107,7 @@ trait NamedTask[+T] extends Task[T] {
   }
   override def toString = ctx.segments.render
 
-  def evaluate(ctx: mill.api.Ctx) = ctx.arg[T](0)
+  def evaluate(ctx: mill.api.Ctx): Result[T] = ctx.arg[T](0)
 
   val ctx = ctx0.withSegments(segments = ctx0.segments ++ Seq(ctx0.segment))
   val inputs = Seq(t)
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index bd26d4744a7..4bbf0475ecb 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -557,13 +557,13 @@ class Evaluator private (
       newEvaluated.append(task)
       val targetInputValues = task.inputs
         .map { x => newResults.getOrElse(x, results(x)) }
-        .collect { case mill.api.Result.Success((v, _), _) => v }
+        .collect { case Result.Success((v, _), sig) => Result.Success(v, sig) }
 
       val res =
         if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
         else {
           val args = new Ctx(
-            args = targetInputValues.toArray[Any].toIndexedSeq,
+            args = targetInputValues.toArray[Result.Success[Any]].toIndexedSeq,
             dest0 = () =>
               paths match {
                 case Some(dest) =>
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 109c56262d6..7e4f9e9d871 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -26,8 +26,6 @@ object RunScript {
           w <- extraWatched
         } yield w
 
-        pprint.log(watched.map(_.pretty))
-        pprint.log(watched2.map(_.pretty))
         (watched ++ watched2, res)
       }
   }
@@ -56,7 +54,6 @@ object RunScript {
       targets: Agg[Task[Any]]
   ): (Seq[Watchable], Either[String, Seq[(Any, Option[ujson.Value])]]) = {
     val (watched, results) = evaluateNamed(evaluator, targets)
-    pprint.log(watched.map(_.pretty))
     // we drop the task name in the inner tuple
     (watched, results.map(_.map(p => (p._1, p._2.map(_._2)))))
   }
@@ -78,15 +75,11 @@ object RunScript {
         case (t: SourceImpl, Result.Success(p: PathRef, _)) => Seq(Watchable.Path(p))
         case (t: InputImpl[_], Result.Success(v, signature)) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
-          println("INPUT FOUND " + pretty)
           Seq(Watchable.Value(() => signature(), signature(), pretty))
       }
       .flatten
       .toSeq
 
-    pprint.log(targets)
-    pprint.log(watched.map(_.pretty))
-
     val errorStr = Evaluator.formatFailing(evaluated)
 
     evaluated.failing.keyCount match {
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index 5af8ba8768b..75d602509d7 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -48,7 +48,6 @@ class MillBuildBootstrap(
       )
     }
 
-    pprint.log(runnerState.frames.map(_.evalWatched.map(_.pretty)))
     Watching.Result(
       watched = runnerState.frames.flatMap(_.evalWatched),
       error = runnerState.errorOpt,

From f1ca4c5dc409f00b778168af8ad904507888c98c Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 00:19:09 +0800
Subject: [PATCH 03/27] .

---
 main/api/src/mill/api/Result.scala | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/main/api/src/mill/api/Result.scala b/main/api/src/mill/api/Result.scala
index d5905fcef99..cb1ec623bf7 100644
--- a/main/api/src/mill/api/Result.scala
+++ b/main/api/src/mill/api/Result.scala
@@ -33,17 +33,7 @@ object Result {
     override def asSuccess: Option[Success[T]] = Some(this)
   }
   object Success{
-    def apply[T](value: => T) = {
-      new Success(
-        value,
-        () => {
-//          if (value.toString.length < 100) {
-//            mill.api.SystemStreams.originalErr.println("Signature " + System.identityHashCode(value))
-//          }
-          value.hashCode()
-        }
-      )
-    }
+    def apply[T](value: => T) = new Success(value, () => value.hashCode())
   }
 
   /**

From 590b09fc9b75e0ebffbcadf1a23617706522f128 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 01:14:37 +0800
Subject: [PATCH 04/27] .

---
 main/api/src/mill/api/Result.scala            |   6 +-
 main/eval/src/mill/eval/Evaluator.scala       |   2 +-
 main/src/mill/main/MainModule.scala           | 113 +++++++-----------
 main/src/mill/main/RunScript.scala            |  47 +-------
 main/util/src/mill/util/Watched.scala         |   9 --
 .../src/mill/runner/MillBuildBootstrap.scala  |  12 +-
 6 files changed, 60 insertions(+), 129 deletions(-)
 delete mode 100644 main/util/src/mill/util/Watched.scala

diff --git a/main/api/src/mill/api/Result.scala b/main/api/src/mill/api/Result.scala
index cb1ec623bf7..b88251b3cb3 100644
--- a/main/api/src/mill/api/Result.scala
+++ b/main/api/src/mill/api/Result.scala
@@ -27,13 +27,13 @@ object Result {
    * @param value The value computed by the task.
    * @tparam T The result type of the computed task.
    */
-  case class Success[+T](value: T, signature: () => Int) extends Result[T] {
-    def map[V](f: T => V): Success[V] = Result.Success(f(value), signature)
+  case class Success[+T](value: T, recalc: () => T) extends Result[T] {
+    def map[V](f: T => V): Success[V] = Result.Success(f(value), () => f(recalc()))
     def flatMap[V](f: T => Result[V]): Result[V] = f(value)
     override def asSuccess: Option[Success[T]] = Some(this)
   }
   object Success{
-    def apply[T](value: => T) = new Success(value, () => value.hashCode())
+    def apply[T](value: => T) = new Success(value, () => value)
   }
 
   /**
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 4bbf0475ecb..c57df7066be 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -423,7 +423,7 @@ class Evaluator private (
         upToDateWorker.map((_, inputsHash)) orElse cached match {
           case Some((v, hashCode)) =>
             val newResults = mutable.LinkedHashMap.empty[Task[_], mill.api.Result[(Any, Int)]]
-            newResults(labelledNamedTask.task) = mill.api.Result.Success((v, hashCode), () => 0)
+            newResults(labelledNamedTask.task) = Result.Success((v, hashCode), () => (v, hashCode))
 
             Evaluated(newResults, Nil, cached = true)
 
diff --git a/main/src/mill/main/MainModule.scala b/main/src/mill/main/MainModule.scala
index a9948128da7..d59e23a83ab 100644
--- a/main/src/mill/main/MainModule.scala
+++ b/main/src/mill/main/MainModule.scala
@@ -2,10 +2,11 @@ package mill.main
 
 import java.util.concurrent.LinkedBlockingQueue
 import mill.{BuildInfo, T}
-import mill.api.{Ctx, PathRef, Result, internal}
+import mill.api.{Ctx, Logger, PathRef, Result, internal}
 import mill.define.{Command, NamedTask, Segments, TargetImpl, Task}
 import mill.eval.{Evaluator, EvaluatorPaths}
-import mill.util.{PrintLogger, Watchable, Watched}
+import mill.main.SelectMode.Separated
+import mill.util.{PrintLogger, Watchable}
 import pprint.{Renderer, Tree, Truncated}
 import ujson.Value
 
@@ -25,32 +26,33 @@ object MainModule {
     }
   }
 
-  def evaluateTasks[T](
-      evaluator: Evaluator,
-      targets: Seq[String],
-      selectMode: SelectMode
-  )(f: Seq[(Any, Option[ujson.Value])] => T): Result[Watched[Unit]] = {
-    RunScript.evaluateTasks(evaluator, targets, selectMode) match {
+  private def show0(evaluator: Evaluator,
+                    targets: Seq[String],
+                    log: Logger,
+                    watch0: Watchable => Unit)
+                   (f: Seq[(Any, Option[(RunScript.TaskName, ujson.Value)])] => ujson.Value) = {
+    RunScript.evaluateTasksNamed(
+      evaluator.withBaseLogger(
+        // When using `show`, redirect all stdout of the evaluated tasks so the
+        // printed JSON is the only thing printed to stdout.
+        evaluator.baseLogger match {
+          case p: PrintLogger => p.withOutStream(p.errorStream)
+          case l => l
+        }
+      ),
+      targets,
+      Separated
+    ) match {
       case Left(err) => Result.Failure(err)
-      case Right((watched, Left(err))) => Result.Failure(err, Some(Watched((), watched)))
-      case Right((watched, Right(res))) =>
-        f(res)
-        Result.Success(Watched((), watched))
-    }
-  }
+      case Right((watched, Left(err))) =>
+        watched.foreach(watch0)
+        Result.Failure(err)
 
-  @internal
-  def evaluateTasksNamed[T](
-      evaluator: Evaluator,
-      targets: Seq[String],
-      selectMode: SelectMode
-  )(f: Seq[(Any, Option[(RunScript.TaskName, ujson.Value)])] => T): Result[Watched[Option[T]]] = {
-    RunScript.evaluateTasksNamed(evaluator, targets, selectMode) match {
-      case Left(err) => Result.Failure(err)
-      case Right((watched, Left(err))) => Result.Failure(err, Some(Watched(None, watched)))
       case Right((watched, Right(res))) =>
-        val fRes = f(res)
-        Result.Success(Watched(Some(fRes), watched))
+        val output = f(res)
+        watched.foreach(watch0)
+        log.outputStream.println(output.render(indent = 2))
+        Result.Success(output)
     }
   }
 }
@@ -61,6 +63,7 @@ object MainModule {
  */
 trait MainModule extends mill.Module {
   protected[mill] val watchedValues = mutable.Buffer.empty[Watchable]
+  protected[mill] val evalWatchedValues = mutable.Buffer.empty[Watchable]
 
   object interp {
 
@@ -84,6 +87,10 @@ trait MainModule extends mill.Module {
     def watch0(w: Watchable): Unit = {
       watchedValues.append(w)
     }
+
+    def evalWatch0(w: Watchable): Unit = {
+      evalWatchedValues.append(w)
+    }
   }
 
 
@@ -272,27 +279,11 @@ trait MainModule extends mill.Module {
    * to integrate Mill into external scripts and tooling.
    */
   def show(evaluator: Evaluator, targets: String*): Command[ujson.Value] = T.command {
-    MainModule.evaluateTasksNamed(
-      evaluator.withBaseLogger(
-        // When using `show`, redirect all stdout of the evaluated tasks so the
-        // printed JSON is the only thing printed to stdout.
-        evaluator.baseLogger match {
-          case p: PrintLogger => p.withOutStream(p.errorStream)
-          case l => l
-        }
-      ),
-      targets,
-      SelectMode.Separated
-    ) { res: Seq[(Any, Option[(String, ujson.Value)])] =>
-      val jsons = res.flatMap(_._2).map(_._2)
-      val output: ujson.Value =
-        if (jsons.size == 1) jsons.head
-        else { ujson.Arr.from(jsons) }
-      T.log.outputStream.println(output.render(indent = 2))
-      output
-    }.map { res: Watched[Option[Value]] =>
-      res.watched.foreach(interp.watch0)
-      res.value.getOrElse(ujson.Null)
+    MainModule.show0(evaluator, targets, T.log, interp.evalWatch0){ res =>
+      res.flatMap(_._2).map(_._2) match{
+        case Seq(single) => single
+        case multiple => multiple
+      }
     }
   }
 
@@ -301,24 +292,8 @@ trait MainModule extends mill.Module {
    * to integrate Mill into external scripts and tooling.
    */
   def showNamed(evaluator: Evaluator, targets: String*): Command[ujson.Value] = T.command {
-    MainModule.evaluateTasksNamed(
-      evaluator.withBaseLogger(
-        // When using `show`, redirect all stdout of the evaluated tasks so the
-        // printed JSON is the only thing printed to stdout.
-        evaluator.baseLogger match {
-          case p: PrintLogger => p.withOutStream(outStream = p.errorStream)
-          case l => l
-        }
-      ),
-      targets,
-      SelectMode.Separated
-    ) { res: Seq[(Any, Option[(String, ujson.Value)])] =>
-      val nameAndJson = res.flatMap(_._2)
-      val output: ujson.Value = ujson.Obj.from(nameAndJson)
-      T.log.outputStream.println(output.render(indent = 2))
-      output
-    }.map { res: Watched[Option[Value]] =>
-      res.value.getOrElse(ujson.Null)
+    MainModule.show0(evaluator, targets, T.log, interp.evalWatch0) { res =>
+      ujson.Obj.from(res.flatMap(_._2))
     }
   }
 
@@ -409,17 +384,19 @@ trait MainModule extends mill.Module {
   }
 
   /**
-   * The `init`` command generates a project based on a Giter8 template. It
+   * The `init` command generates a project based on a Giter8 template. It
    * prompts you to enter project name and creates a folder with that name.
    * You can use it to quickly generate a starter project. There are lots of
    * templates out there for many frameworks and tools!
    */
   def init(evaluator: Evaluator, args: String*): Command[Unit] = T.command {
-    MainModule.evaluateTasks(
+    RunScript.evaluateTasksNamed(
       evaluator,
       Seq("mill.scalalib.giter8.Giter8Module/init") ++ args,
-      selectMode = SelectMode.Single
-    )(identity).map(_.value)
+      SelectMode.Single
+    )
+
+    ()
   }
 
   private type VizWorker = (
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 7e4f9e9d871..7f2c7b1af32 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -2,7 +2,7 @@ package mill.main
 
 import mill.define._
 import mill.eval.{Evaluator, EvaluatorPaths}
-import mill.util.{Watchable, Watched}
+import mill.util.Watchable
 import mill.api.{PathRef, Result}
 import mill.api.Strict.Agg
 
@@ -11,51 +11,13 @@ object RunScript {
 
   type TaskName = String
 
-  def evaluateTasks(
-      evaluator: Evaluator,
-      scriptArgs: Seq[String],
-      selectMode: SelectMode
-  ): Either[String, (Seq[Watchable], Either[String, Seq[(Any, Option[ujson.Value])]])] = {
-    for (targets <- ResolveTasks.resolve(evaluator, scriptArgs, selectMode))
-      yield {
-        val (watched, res) = evaluate(evaluator, Agg.from(targets.distinct))
-
-        val watched2 = for {
-          x <- res.toSeq
-          (Watched(_, extraWatched), _) <- x
-          w <- extraWatched
-        } yield w
-
-        (watched ++ watched2, res)
-      }
-  }
-
   def evaluateTasksNamed[T](
       evaluator: Evaluator,
       scriptArgs: Seq[String],
       selectMode: SelectMode
   ): Either[String, (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])] = {
     for (targets <- ResolveTasks.resolve(evaluator, scriptArgs, selectMode))
-      yield {
-        val (watched, res) = evaluateNamed(evaluator, Agg.from(targets.distinct))
-
-        val watched2 = for {
-          x <- res.toSeq
-          (Watched(_, extraWatched), _) <- x
-          w <- extraWatched
-        } yield w
-
-        (watched ++ watched2, res)
-      }
-  }
-
-  def evaluate(
-      evaluator: Evaluator,
-      targets: Agg[Task[Any]]
-  ): (Seq[Watchable], Either[String, Seq[(Any, Option[ujson.Value])]]) = {
-    val (watched, results) = evaluateNamed(evaluator, targets)
-    // we drop the task name in the inner tuple
-    (watched, results.map(_.map(p => (p._1, p._2.map(_._2)))))
+    yield evaluateNamed(evaluator, Agg.from(targets.distinct))
   }
 
   /**
@@ -68,14 +30,15 @@ object RunScript {
       targets: Agg[Task[Any]]
   ): (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]]) = {
     val evaluated: Evaluator.Results = evaluator.evaluate(targets)
+
     val watched = evaluated.results
       .iterator
       .collect {
         case (t: SourcesImpl, Result.Success(ps: Seq[PathRef], _)) => ps.map(Watchable.Path(_))
         case (t: SourceImpl, Result.Success(p: PathRef, _)) => Seq(Watchable.Path(p))
-        case (t: InputImpl[_], Result.Success(v, signature)) =>
+        case (t: InputImpl[_], Result.Success(v, recalc)) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
-          Seq(Watchable.Value(() => signature(), signature(), pretty))
+          Seq(Watchable.Value(() => recalc().hashCode(), recalc().hashCode(), pretty))
       }
       .flatten
       .toSeq
diff --git a/main/util/src/mill/util/Watched.scala b/main/util/src/mill/util/Watched.scala
deleted file mode 100644
index 93ecc9704a5..00000000000
--- a/main/util/src/mill/util/Watched.scala
+++ /dev/null
@@ -1,9 +0,0 @@
-package mill.util
-
-import mill.api.PathRef
-
-case class Watched[T](value: T, watched: Seq[Watchable])
-object Watched {
-//  implicit def readWrite[T: upickle.default.ReadWriter]: upickle.default.ReadWriter[Watched[T]] =
-//    upickle.default.macroRW[Watched[T]]
-}
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index 75d602509d7..d6583ea28f3 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -49,7 +49,7 @@ class MillBuildBootstrap(
     }
 
     Watching.Result(
-      watched = runnerState.frames.flatMap(_.evalWatched),
+      watched = runnerState.frames.flatMap(f => f.evalWatched ++ f.moduleWatched),
       error = runnerState.errorOpt,
       result = runnerState
     )
@@ -254,7 +254,6 @@ class MillBuildBootstrap(
     val (evaled, evalWatched, moduleWatches) =
       MillBuildBootstrap.evaluateWithWatches(rootModule, evaluator, targetsAndParams)
 
-
     val evalState = RunnerState.Frame(
       evaluator.workerCache.toMap,
       evalWatched,
@@ -333,16 +332,17 @@ object MillBuildBootstrap {
       evaluator: Evaluator,
       targetsAndParams: Seq[String]
   ): (Either[String, Seq[Any]], Seq[Watchable], Seq[Watchable]) = {
-
-    val evalTaskResult = RunScript.evaluateTasks(evaluator, targetsAndParams, SelectMode.Separated)
+    rootModule.evalWatchedValues.clear()
+    val evalTaskResult = RunScript.evaluateTasksNamed(evaluator, targetsAndParams, SelectMode.Separated)
     val moduleWatched = rootModule.watchedValues.toVector
+    val addedEvalWatched = rootModule.evalWatchedValues.toVector
 
     evalTaskResult match {
       case Left(msg) => (Left(msg), Nil, moduleWatched)
       case Right((watched, evaluated)) =>
         evaluated match {
-          case Left(msg) => (Left(msg), watched, moduleWatched)
-          case Right(results) => (Right(results.map(_._1)), watched, moduleWatched)
+          case Left(msg) => (Left(msg), watched ++ addedEvalWatched, moduleWatched)
+          case Right(results) => (Right(results.map(_._1)), watched ++ addedEvalWatched, moduleWatched)
         }
     }
   }

From 467c0f2e5c7960b4bbe342bc28cacbfde3cb465d Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 18:05:07 +0800
Subject: [PATCH 05/27] compiles after moving recalc to Evaluator.EvalResult

---
 bsp/src/mill/bsp/BSP.scala                    |  2 +-
 bsp/worker/src/mill/bsp/worker/Utils.scala    |  4 +-
 main/api/src/mill/api/Ctx.scala               |  6 +-
 main/api/src/mill/api/Result.scala            |  7 +-
 main/define/src/mill/define/Task.scala        | 10 +--
 main/eval/src/mill/eval/Evaluator.scala       | 80 +++++++++++--------
 main/src/mill/main/RunScript.scala            |  6 +-
 main/test/src/mill/main/MainModuleTests.scala | 12 +--
 scalalib/src/mill/scalalib/GenIdeaImpl.scala  |  2 +-
 .../src/mill/scalalib/ResolveDepsTests.scala  | 12 +--
 10 files changed, 74 insertions(+), 67 deletions(-)

diff --git a/bsp/src/mill/bsp/BSP.scala b/bsp/src/mill/bsp/BSP.scala
index 3b16b7b54fb..a71c6844f30 100644
--- a/bsp/src/mill/bsp/BSP.scala
+++ b/bsp/src/mill/bsp/BSP.scala
@@ -95,7 +95,7 @@ object BSP extends ExternalModule with CoursierModule with BspServerStarter {
     val worker = BspWorker(ctx)
 
     worker match {
-      case Result.Success(worker, _) =>
+      case Result.Success(worker) =>
         worker.startBspServer(
           initialEvaluator,
           streams,
diff --git a/bsp/worker/src/mill/bsp/worker/Utils.scala b/bsp/worker/src/mill/bsp/worker/Utils.scala
index 64c54cc0fe6..b05c58ee9c8 100644
--- a/bsp/worker/src/mill/bsp/worker/Utils.scala
+++ b/bsp/worker/src/mill/bsp/worker/Utils.scala
@@ -45,8 +45,8 @@ object Utils {
       results: Evaluator.Results,
       task: mill.define.Task[_]
   ): StatusCode = {
-    results.results(task) match {
-      case Success(_, _) => StatusCode.OK
+    results.results(task).result match {
+      case Success(_) => StatusCode.OK
       case Skipped => StatusCode.CANCELLED
       case _ => StatusCode.ERROR
     }
diff --git a/main/api/src/mill/api/Ctx.scala b/main/api/src/mill/api/Ctx.scala
index c4cc74a22ff..8455a9a9c36 100644
--- a/main/api/src/mill/api/Ctx.scala
+++ b/main/api/src/mill/api/Ctx.scala
@@ -111,7 +111,7 @@ object Ctx {
  * implementation of a `Task`.
  */
 class Ctx(
-    val args: IndexedSeq[Result.Success[_]],
+    val args: IndexedSeq[_],
     dest0: () => os.Path,
     val log: Logger,
     val home: os.Path,
@@ -127,8 +127,8 @@ class Ctx(
     with Ctx.Workspace {
 
   def dest: Path = dest0()
-  def arg[T](index: Int): Result.Success[T] = {
-    if (index >= 0 && index < args.length) args(index).asInstanceOf[Result.Success[T]]
+  def arg[T](index: Int): T = {
+    if (index >= 0 && index < args.length) args(index).asInstanceOf[T]
     else throw new IndexOutOfBoundsException(s"Index $index outside of range 0 - ${args.length}")
   }
 }
diff --git a/main/api/src/mill/api/Result.scala b/main/api/src/mill/api/Result.scala
index b88251b3cb3..5ec9a6e99c3 100644
--- a/main/api/src/mill/api/Result.scala
+++ b/main/api/src/mill/api/Result.scala
@@ -27,14 +27,11 @@ object Result {
    * @param value The value computed by the task.
    * @tparam T The result type of the computed task.
    */
-  case class Success[+T](value: T, recalc: () => T) extends Result[T] {
-    def map[V](f: T => V): Success[V] = Result.Success(f(value), () => f(recalc()))
+  case class Success[+T](value: T) extends Result[T] {
+    def map[V](f: T => V): Success[V] = Result.Success(f(value))
     def flatMap[V](f: T => Result[V]): Result[V] = f(value)
     override def asSuccess: Option[Success[T]] = Some(this)
   }
-  object Success{
-    def apply[T](value: => T) = new Success(value, () => value)
-  }
 
   /**
    * A task execution was skipped because of failures in it's dependencies.
diff --git a/main/define/src/mill/define/Task.scala b/main/define/src/mill/define/Task.scala
index 22758da9d15..9a8ac145b7d 100644
--- a/main/define/src/mill/define/Task.scala
+++ b/main/define/src/mill/define/Task.scala
@@ -56,7 +56,7 @@ object Task {
     val inputs = inputs0
     def evaluate(ctx: mill.api.Ctx) = {
       for (i <- 0 until ctx.args.length)
-        yield ctx.arg[T](i).value
+        yield ctx.arg[T](i)
     }
   }
   private[define] class TraverseCtx[+T, V](
@@ -67,21 +67,19 @@ object Task {
     def evaluate(ctx: mill.api.Ctx) = {
       f(
         for (i <- 0 until ctx.args.length)
-          yield ctx.arg[T](i).value,
+          yield ctx.arg[T](i),
         ctx
       )
     }
   }
 
   private[define] class Mapped[+T, +V](source: Task[T], f: T => V) extends Task[V] {
-    def evaluate(ctx: mill.api.Ctx) = ctx.arg(0).map(f)
+    def evaluate(ctx: mill.api.Ctx) = f(ctx.arg(0))
     val inputs = List(source)
   }
 
   private[define] class Zipped[+T, +V](source1: Task[T], source2: Task[V]) extends Task[(T, V)] {
-    def evaluate(ctx: mill.api.Ctx) = (ctx.arg[T](0), ctx.arg[V](1)) match{
-      case (Result.Success(a, _), Result.Success(b, _)) => (a, b)
-    }
+    def evaluate(ctx: mill.api.Ctx) = (ctx.arg[T](0), ctx.arg[V](1))
     val inputs = List(source1, source2)
   }
 }
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index c57df7066be..86967c2acd5 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -122,14 +122,14 @@ class Evaluator private (
 
     val (sortedGroups, transitive) = Evaluator.plan(goals)
     val evaluated = new Agg.Mutable[Task[_]]
-    val results = mutable.LinkedHashMap.empty[Task[_], mill.api.Result[(Any, Int)]]
+    val results = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(_, Int)]]
     var someTaskFailed: Boolean = false
 
     val timings = mutable.ArrayBuffer.empty[(Either[Task[_], Labelled[_]], Int, Boolean)]
     for (((terminal, group), i) <- sortedGroups.items().zipWithIndex) {
       if (failFast && someTaskFailed) {
         // we exit early and set aborted state for all left tasks
-        group.iterator.foreach { task => results.put(task, Aborted) }
+        group.iterator.foreach { task => results.put(task, Evaluator.EvalResult(Aborted, None)) }
 
       } else {
 
@@ -170,21 +170,21 @@ class Evaluator private (
       evaluated = evaluated,
       transitive = transitive,
       failing = getFailing(sortedGroups, results),
-      results = results.map { case (k, v) => (k, v.map(_._1)) }
+      results = results
     )
   }
 
   def getFailing(
       sortedGroups: MultiBiMap[Either[Task[_], Labelled[Any]], Task[_]],
-      results: collection.Map[Task[_], mill.api.Result[(Any, Int)]]
+      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]]
   ): MultiBiMap.Mutable[Either[Task[_], Labelled[_]], Failing[_]] = {
     val failing = new MultiBiMap.Mutable[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]]
     for ((k, vs) <- sortedGroups.items()) {
       failing.addAll(
         k,
         Loose.Agg.from(
-          vs.items.flatMap(results.get).collect { case f: mill.api.Result.Failing[_] =>
-            f.map(_._1)
+          vs.items.flatMap(results.get).collect { case er @ Evaluator.EvalResult(f: mill.api.Result.Failing[_], _) =>
+            f
           }
         )
       )
@@ -254,7 +254,7 @@ class Evaluator private (
               contextLogger
             )
 
-            if (failFast && res.newResults.values.exists(_.asSuccess.isEmpty)) failed.set(true)
+            if (failFast && res.newResults.values.exists(_.result.asSuccess.isEmpty)) failed.set(true)
 
             val endTime = System.currentTimeMillis()
             timeLog.timeTrace(
@@ -275,16 +275,18 @@ class Evaluator private (
 
       val finishedOptsMap = finishedOpts.toMap
 
-      val results = terminals
+      val results0: Vector[(Task[_], Evaluator.EvalResult[(_, Int)])] = terminals
         .flatMap { t =>
           sortedGroups.lookupKey(t).flatMap { t0 =>
             finishedOptsMap(t) match {
-              case None => Some((t0, Aborted))
+              case None => Some((t0, Evaluator.EvalResult(Aborted, None)))
               case Some(res) => res.newResults.get(t0).map(r => (t0, r))
             }
           }
         }
-        .toMap
+
+      val results: Map[Task[_], Evaluator.EvalResult[(_, Int)]] =
+        results0.toMap
 
       timeLog.close()
 
@@ -304,7 +306,7 @@ class Evaluator private (
   protected def evaluateGroupCached(
       terminal: Terminal,
       group: Agg[Task[_]],
-      results: collection.Map[Task[_], mill.api.Result[(Any, Int)]],
+      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]],
       counterMsg: String,
       zincProblemReporter: Int => Option[CompileProblemReporter],
       testReporter: TestReporter,
@@ -313,7 +315,7 @@ class Evaluator private (
 
     val externalInputsHash = scala.util.hashing.MurmurHash3.orderedHash(
       group.items.flatMap(_.inputs).filter(!group.contains(_))
-        .flatMap(results(_).asSuccess.map(_.value._2))
+        .flatMap(results(_).result.asSuccess.map(_.value._2))
     )
 
     val sideHashes = scala.util.hashing.MurmurHash3.orderedHash(
@@ -422,8 +424,8 @@ class Evaluator private (
 
         upToDateWorker.map((_, inputsHash)) orElse cached match {
           case Some((v, hashCode)) =>
-            val newResults = mutable.LinkedHashMap.empty[Task[_], mill.api.Result[(Any, Int)]]
-            newResults(labelledNamedTask.task) = Result.Success((v, hashCode), () => (v, hashCode))
+            val newResults = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(Any, Int)]]
+            newResults(labelledNamedTask.task) = Evaluator.EvalResult(Result.Success((v, hashCode)), None)
 
             Evaluated(newResults, Nil, cached = true)
 
@@ -449,10 +451,10 @@ class Evaluator private (
               }
 
             newResults(labelledNamedTask.task) match {
-              case mill.api.Result.Failure(_, Some((v, _))) =>
+              case Evaluator.EvalResult(mill.api.Result.Failure(_, Some((v, _))), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
-              case mill.api.Result.Success((v, _), _) =>
+              case Evaluator.EvalResult(mill.api.Result.Success((v, _)), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case _ =>
@@ -512,7 +514,7 @@ class Evaluator private (
 
   protected def evaluateGroup(
       group: Agg[Task[_]],
-      results: collection.Map[Task[_], mill.api.Result[(Any, Int)]],
+      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]],
       inputsHash: Int,
       paths: Option[EvaluatorPaths],
       maybeTargetLabel: Option[String],
@@ -520,10 +522,10 @@ class Evaluator private (
       reporter: Int => Option[CompileProblemReporter],
       testReporter: TestReporter,
       logger: mill.api.Logger
-  ): (mutable.LinkedHashMap[Task[_], mill.api.Result[(Any, Int)]], mutable.Buffer[Task[_]]) = {
+  ): (mutable.LinkedHashMap[Task[_], Evaluator.EvalResult[(Any, Int)]], mutable.Buffer[Task[_]]) = {
 
     val newEvaluated = mutable.Buffer.empty[Task[_]]
-    val newResults = mutable.LinkedHashMap.empty[Task[_], mill.api.Result[(Any, Int)]]
+    val newResults = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(Any, Int)]]
 
     val nonEvaluatedTargets = group.indexed.filterNot(results.contains)
 
@@ -557,7 +559,7 @@ class Evaluator private (
       newEvaluated.append(task)
       val targetInputValues = task.inputs
         .map { x => newResults.getOrElse(x, results(x)) }
-        .collect { case Result.Success((v, _), sig) => Result.Success(v, sig) }
+        .collect { case Evaluator.EvalResult(Result.Success((v, _)), _) => Result.Success(v) }
 
       val res =
         if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
@@ -600,13 +602,16 @@ class Evaluator private (
 
         }
 
-      newResults(task) = for (v <- res) yield {
-        (
-          v,
-          if (task.isInstanceOf[Worker[_]]) inputsHash
-          else v.##
-        )
-      }
+      newResults(task) = Evaluator.EvalResult(
+        for (v <- res) yield {
+          (
+            v,
+            if (task.isInstanceOf[Worker[_]]) inputsHash
+            else v.##
+          )
+        },
+        None
+      )
     }
 
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>
@@ -764,20 +769,27 @@ object Evaluator {
     )
   }
 
+  case class EvalResult[T](result: Result[T],
+                           recalcOpt: Option[() => mill.api.Result[T]]){
+    def map[V](f: T => V) = EvalResult[V](
+      result.map(f),
+      recalcOpt.map(r => () => r().map(f))
+    )
+  }
   case class Results(
       rawValues: Seq[mill.api.Result[Any]],
       evaluated: Agg[Task[_]],
       transitive: Agg[Task[_]],
       failing: MultiBiMap[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]],
-      results: collection.Map[Task[_], mill.api.Result[Any]]
+      results: collection.Map[Task[_], EvalResult[_]]
   ) {
-    def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v, _) => v }
+    def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v) => v }
     private def copy(
         rawValues: Seq[Result[Any]] = rawValues,
         evaluated: Agg[Task[_]] = evaluated,
         transitive: Agg[Task[_]] = transitive,
         failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[_]] = failing,
-        results: collection.Map[Task[_], Result[Any]] = results
+        results: collection.Map[Task[_], EvalResult[_]]
     ): Results = new Results(
       rawValues,
       evaluated,
@@ -793,7 +805,7 @@ object Evaluator {
         Agg[Task[_]],
         Agg[Task[_]],
         MultiBiMap[Either[Task[_], Labelled[_]], Failing[_]],
-        collection.Map[Task[_], Result[Any]]
+          collection.Map[Task[_], EvalResult[_]]
     )] = Some((
       results.rawValues,
       results.evaluated,
@@ -844,12 +856,12 @@ object Evaluator {
   }
 
   case class Evaluated(
-      newResults: collection.Map[Task[_], Result[(Any, Int)]],
+      newResults: collection.Map[Task[_], EvalResult[(_, Int)]],
       newEvaluated: Seq[Task[_]],
       cached: Boolean
   ) {
     private[Evaluator] def copy(
-        newResults: collection.Map[Task[_], Result[(Any, Int)]] = newResults,
+        newResults: collection.Map[Task[_], EvalResult[(_, Int)]],
         newEvaluated: Seq[Task[_]] = newEvaluated,
         cached: Boolean = cached
     ): Evaluated = new Evaluated(newResults, newEvaluated, cached)
@@ -857,7 +869,7 @@ object Evaluator {
 
   object Evaluated {
     private[Evaluator] def unapply(evaluated: Evaluated)
-        : Option[(collection.Map[Task[_], Result[(Any, Int)]], Seq[Task[_]], Boolean)] =
+        : Option[(collection.Map[Task[_], EvalResult[(_, Int)]], Seq[Task[_]], Boolean)] =
       Some((evaluated.newResults, evaluated.newEvaluated, evaluated.cached))
   }
 
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 7f2c7b1af32..37b9309e028 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -34,9 +34,9 @@ object RunScript {
     val watched = evaluated.results
       .iterator
       .collect {
-        case (t: SourcesImpl, Result.Success(ps: Seq[PathRef], _)) => ps.map(Watchable.Path(_))
-        case (t: SourceImpl, Result.Success(p: PathRef, _)) => Seq(Watchable.Path(p))
-        case (t: InputImpl[_], Result.Success(v, recalc)) =>
+        case (t: SourcesImpl, Evaluator.EvalResult(Result.Success(ps: Seq[PathRef]), None)) => ps.map(Watchable.Path(_))
+        case (t: SourceImpl, Evaluator.EvalResult(Result.Success(p: PathRef), None)) => Seq(Watchable.Path(p))
+        case (t: InputImpl[_], Evaluator.EvalResult(Result.Success(v), Some(recalc))) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
           Seq(Watchable.Value(() => recalc().hashCode(), recalc().hashCode(), pretty))
       }
diff --git a/main/test/src/mill/main/MainModuleTests.scala b/main/test/src/mill/main/MainModuleTests.scala
index 4572e4247a6..aca9b114add 100644
--- a/main/test/src/mill/main/MainModuleTests.scala
+++ b/main/test/src/mill/main/MainModuleTests.scala
@@ -49,7 +49,7 @@ object MainModuleTests extends TestSuite {
       val eval = new TestEvaluator(mainModule)
       test("single") {
         val res = eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello")))
-        val Result.Success(value: String, _) = res.rawValues.head
+        val Result.Success(value: String) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -59,7 +59,7 @@ object MainModuleTests extends TestSuite {
       test("multi") {
         val res =
           eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello", "hello2")))
-        val Result.Success(value: String, _) = res.rawValues.head
+        val Result.Success(value: String) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -77,7 +77,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value, _) = results.rawValues.head
+        val Result.Success(value) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq("hello", "world")))
       }
@@ -92,7 +92,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value, _) = results.rawValues.head
+        val Result.Success(value) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq(
           ujson.Arr.from(Seq("hello", "world")),
@@ -109,7 +109,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value, _) = results.rawValues.head
+        val Result.Success(value) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world"))
@@ -126,7 +126,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value, _) = results.rawValues.head
+        val Result.Success(value) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world")),
diff --git a/scalalib/src/mill/scalalib/GenIdeaImpl.scala b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
index ae6b46793a5..4f0c97cc613 100755
--- a/scalalib/src/mill/scalalib/GenIdeaImpl.scala
+++ b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
@@ -105,7 +105,7 @@ case class GenIdeaImpl(
             val millDeps = BuildInfo.millEmbeddedDeps.split(",").map(d => ivy"$d").map(dep =>
               BoundDep(Lib.depToDependency(dep, BuildInfo.scalaVersion, ""), dep.force)
             )
-            val Result.Success(res, _) = scalalib.Lib.resolveDependencies(
+            val Result.Success(res) = scalalib.Lib.resolveDependencies(
               repositories = repos.toList,
               deps = millDeps,
               sources = false,
diff --git a/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala b/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
index 61404c4add5..3fe25078286 100644
--- a/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
+++ b/scalalib/test/src/mill/scalalib/ResolveDepsTests.scala
@@ -19,20 +19,20 @@ object ResolveDepsTests extends TestSuite {
   val tests = Tests {
     "resolveValidDeps" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3")
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(paths.nonEmpty)
     }
 
     "resolveValidDepsWithClassifier" - {
       val deps = Agg(ivy"org.lwjgl:lwjgl:3.1.1;classifier=natives-macos")
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(paths.nonEmpty)
       assert(paths.items.next().path.toString.contains("natives-macos"))
     }
 
     "resolveTransitiveRuntimeDeps" - {
       val deps = Agg(ivy"org.mockito:mockito-core:2.7.22")
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(paths.nonEmpty)
       assert(paths.exists(_.path.toString.contains("objenesis")))
       assert(paths.exists(_.path.toString.contains("byte-buddy")))
@@ -40,13 +40,13 @@ object ResolveDepsTests extends TestSuite {
 
     "excludeTransitiveDeps" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".exclude("com.lihaoyi" -> "fansi_2.12"))
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(!paths.exists(_.path.toString.contains("fansi_2.12")))
     }
 
     "excludeTransitiveDepsByOrg" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".excludeOrg("com.lihaoyi"))
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(!paths.exists(path =>
         path.path.toString.contains("com/lihaoyi") && !path.path.toString.contains("pprint_2.12")
       ))
@@ -54,7 +54,7 @@ object ResolveDepsTests extends TestSuite {
 
     "excludeTransitiveDepsByName" - {
       val deps = Agg(ivy"com.lihaoyi::pprint:0.5.3".excludeName("fansi_2.12"))
-      val Success(paths, _) = evalDeps(deps)
+      val Success(paths) = evalDeps(deps)
       assert(!paths.exists(_.path.toString.contains("fansi_2.12")))
     }
 

From 02f0cefd4ab37b827e52a60e2a02ee2d202a4714 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 18:18:10 +0800
Subject: [PATCH 06/27] wip

---
 example/basic/1-simple-scala/build.sc   | 125 +-----------------------
 main/define/src/mill/define/Task.scala  |   8 +-
 main/eval/src/mill/eval/Evaluator.scala |   5 +
 3 files changed, 14 insertions(+), 124 deletions(-)

diff --git a/example/basic/1-simple-scala/build.sc b/example/basic/1-simple-scala/build.sc
index 3be43e9ade7..f0cbc900579 100644
--- a/example/basic/1-simple-scala/build.sc
+++ b/example/basic/1-simple-scala/build.sc
@@ -1,124 +1,9 @@
 
-import mill._, scalalib._
+import mill._
 
-object foo extends RootModule with ScalaModule {
-  def scalaVersion = "2.13.8"
-  def ivyDeps = Agg(
-    ivy"com.lihaoyi::scalatags:0.8.2",
-    ivy"com.lihaoyi::mainargs:0.4.0"
-  )
+interp.watchValue(System.currentTimeMillis() / 5000)
 
-  object test extends Tests {
-    def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.7.11")
-    def testFramework = "utest.runner.Framework"
-  }
-}
+println("Setting up build.sc")
+def foo = T.input{ System.currentTimeMillis() / 1000 }
 
-// This is a basic Mill build for a single `ScalaModule`, with two
-// third-party dependencies and a test suite using the uTest framework. As a
-// single-module project, it `extends RootModule` to mark `object foo` as the
-// top-level module in the build. This lets us directly perform operations
-// `./mill compile` or `./mill run` without needing to prefix it as
-// `foo.compile` or `foo.run`.
-//
-// You can download this example project using the *download* link above
-// if you want to try out the commands below yourself. The only requirement is
-// that you have some version of the JVM installed; the `./mill` script takes
-// care of any further dependencies that need to be downloaded.
-//
-// The source code for this module lives in the `src/` folder.
-// Output for this module (compiled files, resolved dependency lists, ...)
-// lives in `out/`.
-//
-// This example project uses two third-party dependencies - MainArgs for CLI
-// argument parsing, Scalatags for HTML generation - and uses them to wrap a
-// given input string in HTML templates with proper escaping.
-//
-// You can run `assembly` to generate a standalone executable jar, which then
-// can be run from the command line or deployed to be run elsewhere.
-
-/** Usage
-
-> ./mill resolve _ # List what tasks are available to run
-assembly
-...
-clean
-...
-compile
-...
-run
-...
-show
-...
-inspect
-...
-
-> ./mill inspect compile # Show documentation and inputs of a task
-compile(ScalaModule.scala:...)
-    Compiles the current module to generate compiled classfiles/bytecode.
-Inputs:
-    scalaVersion
-    upstreamCompileOutput
-    allSourceFiles
-    compileClasspath
-
-> ./mill compile # compile sources into classfiles
-...
-compiling 1 Scala source to...
-
-> ./mill run # run the main method, if any
-error: Missing argument: --text <str>
-
-> ./mill run --text hello
-<h1>hello</h1>
-
-> ./mill test
-...
-+ foo.FooTests.simple ...  <h1>hello</h1>
-+ foo.FooTests.escaping ...  <h1>&lt;hello&gt;</h1>
-
-> ./mill assembly # bundle classfiles and libraries into a jar for deployment
-
-> ./mill show assembly # show the output of the assembly task
-".../out/assembly.dest/out.jar"
-
-> java -jar ./out/assembly.dest/out.jar --text hello
-<h1>hello</h1>
-
-> ./out/assembly.dest/out.jar --text hello # mac/linux
-<h1>hello</h1>
-
-*/
-
-// The output of every Mill task is stored in the `out/` folder under a name
-// corresponding to the task that created it. e.g. The `assembly` task puts its
-// metadata output in `out/assembly.json`, and its output files in
-// `out/assembly.dest`. You can also use `show` to make Mill print out the
-// metadata output for a particular task.
-//
-// Additional Mill tasks you would likely need include:
-//
-// [source,bash]
-// ----
-// $ mill runBackground # run the main method in the background
-//
-// $ mill clean <task>  # delete the cached output of a task, terminate any runBackground
-//
-// $ mill launcher      # prepares a foo/launcher.dest/run you can run later
-//
-// $ mill jar           # bundle the classfiles into a jar suitable for publishing
-//
-// $ mill -i console    # start a Scala console within your project
-//
-// $ mill -i repl       # start an Ammonite Scala REPL within your project
-// ----
-//
-// You can run `+mill resolve __+` to see a full list of the different tasks that
-// are available, `+mill resolve _+` to see the tasks within `foo`,
-// `mill inspect compile` to inspect a task's doc-comment documentation or what
-// it depends on, or `mill show foo.scalaVersion` to show the output of any task.
-//
-// The most common *tasks* that Mill can run are cached *targets*, such as
-// `compile`, and un-cached *commands* such as `foo.run`. Targets do not
-// re-evaluate unless one of their inputs changes, whereas commands re-run every
-// time.
\ No newline at end of file
+def bar = T{ foo() + " seconds since the epoch" }
\ No newline at end of file
diff --git a/main/define/src/mill/define/Task.scala b/main/define/src/mill/define/Task.scala
index 9a8ac145b7d..7a94d6d6c72 100644
--- a/main/define/src/mill/define/Task.scala
+++ b/main/define/src/mill/define/Task.scala
@@ -56,7 +56,7 @@ object Task {
     val inputs = inputs0
     def evaluate(ctx: mill.api.Ctx) = {
       for (i <- 0 until ctx.args.length)
-        yield ctx.arg[T](i)
+        yield ctx.args(i).asInstanceOf[T]
     }
   }
   private[define] class TraverseCtx[+T, V](
@@ -67,7 +67,7 @@ object Task {
     def evaluate(ctx: mill.api.Ctx) = {
       f(
         for (i <- 0 until ctx.args.length)
-          yield ctx.arg[T](i),
+          yield ctx.args(i).asInstanceOf[T],
         ctx
       )
     }
@@ -79,7 +79,7 @@ object Task {
   }
 
   private[define] class Zipped[+T, +V](source1: Task[T], source2: Task[V]) extends Task[(T, V)] {
-    def evaluate(ctx: mill.api.Ctx) = (ctx.arg[T](0), ctx.arg[V](1))
+    def evaluate(ctx: mill.api.Ctx) = (ctx.arg(0), ctx.arg(1))
     val inputs = List(source1, source2)
   }
 }
@@ -105,7 +105,7 @@ trait NamedTask[+T] extends Task[T] {
   }
   override def toString = ctx.segments.render
 
-  def evaluate(ctx: mill.api.Ctx): Result[T] = ctx.arg[T](0)
+  def evaluate(ctx: mill.api.Ctx) = ctx.arg[T](0)
 
   val ctx = ctx0.withSegments(segments = ctx0.segments ++ Seq(ctx0.segment))
   val inputs = Seq(t)
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 86967c2acd5..f3f576371f7 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -452,9 +452,11 @@ class Evaluator private (
 
             newResults(labelledNamedTask.task) match {
               case Evaluator.EvalResult(mill.api.Result.Failure(_, Some((v, _))), _) =>
+                pprint.log(v)
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case Evaluator.EvalResult(mill.api.Result.Success((v, _)), _) =>
+                pprint.log(v)
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case _ =>
@@ -602,6 +604,7 @@ class Evaluator private (
 
         }
 
+      pprint.log(res)
       newResults(task) = Evaluator.EvalResult(
         for (v <- res) yield {
           (
@@ -612,6 +615,8 @@ class Evaluator private (
         },
         None
       )
+
+      pprint.log(newResults(task))
     }
 
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>

From 0524586d359dae1e83308da5c23a28869dbd8eb7 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 18:20:32 +0800
Subject: [PATCH 07/27] wip

---
 main/eval/src/mill/eval/Evaluator.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index f3f576371f7..2585b9eaafd 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -170,7 +170,7 @@ class Evaluator private (
       evaluated = evaluated,
       transitive = transitive,
       failing = getFailing(sortedGroups, results),
-      results = results
+      results = results.map { case (k, v) => (k, v.map(_._1)) }
     )
   }
 

From f2a797e0472e3eb254b56a343bfaeebc2b81bb5f Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 18:47:26 +0800
Subject: [PATCH 08/27] things pass converted to Val

---
 main/eval/src/mill/eval/Evaluator.scala       | 78 +++++++++----------
 main/src/mill/main/RunScript.scala            | 10 +--
 .../src/mill/runner/MillBuildBootstrap.scala  |  4 +-
 3 files changed, 43 insertions(+), 49 deletions(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 2585b9eaafd..683a96c2b8a 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -42,7 +42,7 @@ class Evaluator private (
     _scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])]
 ) {
 
-  import Evaluator.Terminal
+  import Evaluator._
 
   def home: os.Path = _home
 
@@ -122,14 +122,14 @@ class Evaluator private (
 
     val (sortedGroups, transitive) = Evaluator.plan(goals)
     val evaluated = new Agg.Mutable[Task[_]]
-    val results = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(_, Int)]]
+    val results = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
     var someTaskFailed: Boolean = false
 
     val timings = mutable.ArrayBuffer.empty[(Either[Task[_], Labelled[_]], Int, Boolean)]
     for (((terminal, group), i) <- sortedGroups.items().zipWithIndex) {
       if (failFast && someTaskFailed) {
         // we exit early and set aborted state for all left tasks
-        group.iterator.foreach { task => results.put(task, Evaluator.EvalResult(Aborted, None)) }
+        group.iterator.foreach { task => results.put(task, TaskResult(Aborted, None)) }
 
       } else {
 
@@ -154,7 +154,7 @@ class Evaluator private (
           logger = contextLogger
         )
         someTaskFailed =
-          someTaskFailed || newResults.exists(task => !task._2.isInstanceOf[Success[_]])
+          someTaskFailed || newResults.exists(task => !task._2.result.isInstanceOf[Success[_]])
 
         for (ev <- newEvaluated) evaluated.append(ev)
         for ((k, v) <- newResults) results.put(k, v)
@@ -165,8 +165,9 @@ class Evaluator private (
     }
 
     Evaluator.writeTimings(timings.toSeq, outPath)
+
     Evaluator.Results(
-      rawValues = goals.indexed.map(results(_).map(_._1)),
+      rawValues = goals.indexed.map(results(_).result.map(_._1)),
       evaluated = evaluated,
       transitive = transitive,
       failing = getFailing(sortedGroups, results),
@@ -176,14 +177,14 @@ class Evaluator private (
 
   def getFailing(
       sortedGroups: MultiBiMap[Either[Task[_], Labelled[Any]], Task[_]],
-      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]]
+      results: collection.Map[Task[_], TaskResult[(Val, Int)]]
   ): MultiBiMap.Mutable[Either[Task[_], Labelled[_]], Failing[_]] = {
     val failing = new MultiBiMap.Mutable[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]]
     for ((k, vs) <- sortedGroups.items()) {
       failing.addAll(
         k,
         Loose.Agg.from(
-          vs.items.flatMap(results.get).collect { case er @ Evaluator.EvalResult(f: mill.api.Result.Failing[_], _) =>
+          vs.items.flatMap(results.get).collect { case er @ TaskResult(f: mill.api.Result.Failing[_], _) =>
             f
           }
         )
@@ -275,17 +276,17 @@ class Evaluator private (
 
       val finishedOptsMap = finishedOpts.toMap
 
-      val results0: Vector[(Task[_], Evaluator.EvalResult[(_, Int)])] = terminals
+      val results0: Vector[(Task[_], TaskResult[(Val, Int)])] = terminals
         .flatMap { t =>
           sortedGroups.lookupKey(t).flatMap { t0 =>
             finishedOptsMap(t) match {
-              case None => Some((t0, Evaluator.EvalResult(Aborted, None)))
+              case None => Some((t0, TaskResult(Aborted, None)))
               case Some(res) => res.newResults.get(t0).map(r => (t0, r))
             }
           }
         }
 
-      val results: Map[Task[_], Evaluator.EvalResult[(_, Int)]] =
+      val results: Map[Task[_], TaskResult[(Val, Int)]] =
         results0.toMap
 
       timeLog.close()
@@ -306,7 +307,7 @@ class Evaluator private (
   protected def evaluateGroupCached(
       terminal: Terminal,
       group: Agg[Task[_]],
-      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]],
+      results: collection.Map[Task[_], TaskResult[(Val, Int)]],
       counterMsg: String,
       zincProblemReporter: Int => Option[CompileProblemReporter],
       testReporter: TestReporter,
@@ -424,8 +425,8 @@ class Evaluator private (
 
         upToDateWorker.map((_, inputsHash)) orElse cached match {
           case Some((v, hashCode)) =>
-            val newResults = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(Any, Int)]]
-            newResults(labelledNamedTask.task) = Evaluator.EvalResult(Result.Success((v, hashCode)), None)
+            val newResults = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
+            newResults(labelledNamedTask.task) = TaskResult(Result.Success((Val(v), hashCode)), None)
 
             Evaluated(newResults, Nil, cached = true)
 
@@ -451,12 +452,10 @@ class Evaluator private (
               }
 
             newResults(labelledNamedTask.task) match {
-              case Evaluator.EvalResult(mill.api.Result.Failure(_, Some((v, _))), _) =>
-                pprint.log(v)
+              case TaskResult(mill.api.Result.Failure(_, Some((v, _))), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
-              case Evaluator.EvalResult(mill.api.Result.Success((v, _)), _) =>
-                pprint.log(v)
+              case TaskResult(mill.api.Result.Success((v, _)), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case _ =>
@@ -483,7 +482,7 @@ class Evaluator private (
   }
 
   def handleTaskResult(
-      v: Any,
+      v: Val,
       hashCode: Int,
       metaPath: os.Path,
       inputsHash: Int,
@@ -499,9 +498,9 @@ class Evaluator private (
           .task
           .writerOpt
           .asInstanceOf[Option[upickle.default.Writer[Any]]]
-          .map(w => upickle.default.writeJs(v)(w) -> v)
+          .map{w => upickle.default.writeJs(v.value)(w)}
 
-        for ((json, _) <- terminalResult) {
+        for (json <- terminalResult) {
           os.write.over(
             metaPath,
             upickle.default.stream(
@@ -516,7 +515,7 @@ class Evaluator private (
 
   protected def evaluateGroup(
       group: Agg[Task[_]],
-      results: collection.Map[Task[_], Evaluator.EvalResult[(_, Int)]],
+      results: collection.Map[Task[_], TaskResult[(Val, Int)]],
       inputsHash: Int,
       paths: Option[EvaluatorPaths],
       maybeTargetLabel: Option[String],
@@ -524,10 +523,10 @@ class Evaluator private (
       reporter: Int => Option[CompileProblemReporter],
       testReporter: TestReporter,
       logger: mill.api.Logger
-  ): (mutable.LinkedHashMap[Task[_], Evaluator.EvalResult[(Any, Int)]], mutable.Buffer[Task[_]]) = {
+  ): (mutable.LinkedHashMap[Task[_], TaskResult[(Val, Int)]], mutable.Buffer[Task[_]]) = {
 
     val newEvaluated = mutable.Buffer.empty[Task[_]]
-    val newResults = mutable.LinkedHashMap.empty[Task[_], Evaluator.EvalResult[(Any, Int)]]
+    val newResults = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
 
     val nonEvaluatedTargets = group.indexed.filterNot(results.contains)
 
@@ -537,7 +536,7 @@ class Evaluator private (
         target <- nonEvaluatedTargets
         item <- target.inputs.filterNot(group.contains)
       } yield results(item).map(_._1)
-      inputResults.forall(_.isInstanceOf[mill.api.Result.Success[_]])
+      inputResults.forall(_.result.isInstanceOf[mill.api.Result.Success[_]])
     }
 
     val tickerPrefix = maybeTargetLabel.map { targetLabel =>
@@ -561,13 +560,13 @@ class Evaluator private (
       newEvaluated.append(task)
       val targetInputValues = task.inputs
         .map { x => newResults.getOrElse(x, results(x)) }
-        .collect { case Evaluator.EvalResult(Result.Success((v, _)), _) => Result.Success(v) }
+        .collect { case TaskResult(Result.Success((v, _)), _) => v }
 
       val res =
         if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
         else {
           val args = new Ctx(
-            args = targetInputValues.toArray[Result.Success[Any]].toIndexedSeq,
+            args = targetInputValues.map(_.value).toIndexedSeq,
             dest0 = () =>
               paths match {
                 case Some(dest) =>
@@ -588,11 +587,8 @@ class Evaluator private (
             override def jobs: Int = effectiveThreadCount
           }
 
-          val out = System.out
-          val in = System.in
-          val err = System.err
           mill.api.SystemStreams.withStreams(multiLogger.systemStreams) {
-            try task.evaluate(args)
+            try task.evaluate(args).map(Val(_))
             catch {
               case NonFatal(e) =>
                 mill.api.Result.Exception(
@@ -601,11 +597,9 @@ class Evaluator private (
                 )
             }
           }
-
         }
 
-      pprint.log(res)
-      newResults(task) = Evaluator.EvalResult(
+      newResults(task) = TaskResult(
         for (v <- res) yield {
           (
             v,
@@ -616,7 +610,6 @@ class Evaluator private (
         None
       )
 
-      pprint.log(newResults(task))
     }
 
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>
@@ -774,19 +767,20 @@ object Evaluator {
     )
   }
 
-  case class EvalResult[T](result: Result[T],
+  case class TaskResult[T](result: Result[T],
                            recalcOpt: Option[() => mill.api.Result[T]]){
-    def map[V](f: T => V) = EvalResult[V](
+    def map[V](f: T => V) = TaskResult[V](
       result.map(f),
       recalcOpt.map(r => () => r().map(f))
     )
   }
+  case class Val(value: Any)
   case class Results(
       rawValues: Seq[mill.api.Result[Any]],
       evaluated: Agg[Task[_]],
       transitive: Agg[Task[_]],
       failing: MultiBiMap[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]],
-      results: collection.Map[Task[_], EvalResult[_]]
+      results: collection.Map[Task[_], TaskResult[Val]]
   ) {
     def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v) => v }
     private def copy(
@@ -794,7 +788,7 @@ object Evaluator {
         evaluated: Agg[Task[_]] = evaluated,
         transitive: Agg[Task[_]] = transitive,
         failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[_]] = failing,
-        results: collection.Map[Task[_], EvalResult[_]]
+        results: collection.Map[Task[_], TaskResult[Val]]
     ): Results = new Results(
       rawValues,
       evaluated,
@@ -810,7 +804,7 @@ object Evaluator {
         Agg[Task[_]],
         Agg[Task[_]],
         MultiBiMap[Either[Task[_], Labelled[_]], Failing[_]],
-          collection.Map[Task[_], EvalResult[_]]
+          collection.Map[Task[_], TaskResult[_]]
     )] = Some((
       results.rawValues,
       results.evaluated,
@@ -861,12 +855,12 @@ object Evaluator {
   }
 
   case class Evaluated(
-      newResults: collection.Map[Task[_], EvalResult[(_, Int)]],
+      newResults: collection.Map[Task[_], TaskResult[(Val, Int)]],
       newEvaluated: Seq[Task[_]],
       cached: Boolean
   ) {
     private[Evaluator] def copy(
-        newResults: collection.Map[Task[_], EvalResult[(_, Int)]],
+        newResults: collection.Map[Task[_], TaskResult[(Val, Int)]],
         newEvaluated: Seq[Task[_]] = newEvaluated,
         cached: Boolean = cached
     ): Evaluated = new Evaluated(newResults, newEvaluated, cached)
@@ -874,7 +868,7 @@ object Evaluator {
 
   object Evaluated {
     private[Evaluator] def unapply(evaluated: Evaluated)
-        : Option[(collection.Map[Task[_], EvalResult[(_, Int)]], Seq[Task[_]], Boolean)] =
+        : Option[(collection.Map[Task[_], TaskResult[(Val, Int)]], Seq[Task[_]], Boolean)] =
       Some((evaluated.newResults, evaluated.newEvaluated, evaluated.cached))
   }
 
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 37b9309e028..56382384525 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -5,7 +5,7 @@ import mill.eval.{Evaluator, EvaluatorPaths}
 import mill.util.Watchable
 import mill.api.{PathRef, Result}
 import mill.api.Strict.Agg
-
+import Evaluator._
 
 object RunScript {
 
@@ -29,14 +29,14 @@ object RunScript {
       evaluator: Evaluator,
       targets: Agg[Task[Any]]
   ): (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]]) = {
-    val evaluated: Evaluator.Results = evaluator.evaluate(targets)
+    val evaluated: Results = evaluator.evaluate(targets)
 
     val watched = evaluated.results
       .iterator
       .collect {
-        case (t: SourcesImpl, Evaluator.EvalResult(Result.Success(ps: Seq[PathRef]), None)) => ps.map(Watchable.Path(_))
-        case (t: SourceImpl, Evaluator.EvalResult(Result.Success(p: PathRef), None)) => Seq(Watchable.Path(p))
-        case (t: InputImpl[_], Evaluator.EvalResult(Result.Success(v), Some(recalc))) =>
+        case (t: SourcesImpl, TaskResult(Result.Success(Val(ps: Seq[PathRef])), None)) => ps.map(Watchable.Path(_))
+        case (t: SourceImpl, TaskResult(Result.Success(Val(p: PathRef)), None)) => Seq(Watchable.Path(p))
+        case (t: InputImpl[_], TaskResult(Result.Success(Val(v)), Some(recalc))) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
           Seq(Watchable.Value(() => recalc().hashCode(), recalc().hashCode(), pretty))
       }
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index 4b0b8f22b9c..36455e6b3c2 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -194,8 +194,8 @@ class MillBuildBootstrap(
 
       case (
             Right(Seq(
-              runClasspath: Seq[PathRef],
-              scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])]
+              Evaluator.Val(runClasspath: Seq[PathRef]),
+              Evaluator.Val(scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])])
             )),
             evalWatches,
             moduleWatches

From a823018569553b0a36a38202961155d41a5ca1e2 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 18:48:23 +0800
Subject: [PATCH 09/27] things pass converted to Val

---
 main/eval/src/mill/eval/Evaluator.scala | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 683a96c2b8a..f66b82abfaa 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -599,15 +599,16 @@ class Evaluator private (
           }
         }
 
+      def makeTuple() = for (v <- res) yield {
+        (
+          v,
+          if (task.isInstanceOf[Worker[_]]) inputsHash
+          else v.##
+        )
+      }
       newResults(task) = TaskResult(
-        for (v <- res) yield {
-          (
-            v,
-            if (task.isInstanceOf[Worker[_]]) inputsHash
-            else v.##
-          )
-        },
-        None
+        makeTuple(),
+        Option.when(task.isInstanceOf[InputImpl[_]])(() => makeTuple())
       )
 
     }

From bd4326fe6685f19b82ce9153534f83e6d7159c27 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Tue, 2 May 2023 19:19:48 +0800
Subject: [PATCH 10/27] fix crash

---
 example/basic/1-simple-scala/build.sc   |   4 +-
 main/eval/src/mill/eval/Evaluator.scala | 177 +++++++++++++-----------
 main/src/mill/main/RunScript.scala      |   6 +-
 3 files changed, 101 insertions(+), 86 deletions(-)

diff --git a/example/basic/1-simple-scala/build.sc b/example/basic/1-simple-scala/build.sc
index f0cbc900579..e9b3366cd8b 100644
--- a/example/basic/1-simple-scala/build.sc
+++ b/example/basic/1-simple-scala/build.sc
@@ -1,9 +1,9 @@
 
 import mill._
 
-interp.watchValue(System.currentTimeMillis() / 5000)
+interp.watchValue{ System.currentTimeMillis() / 5000 }
 
 println("Setting up build.sc")
 def foo = T.input{ System.currentTimeMillis() / 1000 }
 
-def bar = T{ foo() + " seconds since the epoch" }
\ No newline at end of file
+def bar = T{ foo() + " seconds since the epoch" }
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index f66b82abfaa..5f9b14dff3d 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -354,7 +354,7 @@ class Evaluator private (
       case Left(task) =>
         val (newResults, newEvaluated) = evaluateGroup(
           group,
-          results,
+          results.toMap,
           inputsHash,
           paths = None,
           maybeTargetLabel = None,
@@ -440,7 +440,7 @@ class Evaluator private (
               Evaluator.dynamicTickerPrefix.withValue(s"[$counterMsg] $targetLabel > ") {
                 evaluateGroup(
                   group,
-                  results,
+                  results.toMap,
                   inputsHash,
                   paths = Some(paths),
                   maybeTargetLabel = Some(targetLabel),
@@ -491,7 +491,7 @@ class Evaluator private (
     labelledNamedTask.task.asWorker match {
       case Some(w) =>
         workerCache.synchronized {
-          workerCache.update(w.ctx.segments, (inputsHash, v))
+          workerCache.update(w.ctx.segments, (inputsHash, v.value))
         }
       case None =>
         val terminalResult = labelledNamedTask
@@ -525,94 +525,97 @@ class Evaluator private (
       logger: mill.api.Logger
   ): (mutable.LinkedHashMap[Task[_], TaskResult[(Val, Int)]], mutable.Buffer[Task[_]]) = {
 
-    val newEvaluated = mutable.Buffer.empty[Task[_]]
-    val newResults = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
+    def computeAll() = {
+      val newEvaluated = mutable.Buffer.empty[Task[_]]
+      val newResults = mutable.LinkedHashMap.empty[Task[_], Result[(Val, Int)]]
 
-    val nonEvaluatedTargets = group.indexed.filterNot(results.contains)
+      val nonEvaluatedTargets = group.indexed.filterNot(results.contains)
 
-    // should we log progress?
-    val logRun = maybeTargetLabel.isDefined && {
-      val inputResults = for {
-        target <- nonEvaluatedTargets
-        item <- target.inputs.filterNot(group.contains)
-      } yield results(item).map(_._1)
-      inputResults.forall(_.result.isInstanceOf[mill.api.Result.Success[_]])
-    }
+      // should we log progress?
+      val logRun = maybeTargetLabel.isDefined && {
+        val inputResults = for {
+          target <- nonEvaluatedTargets
+          item <- target.inputs.filterNot(group.contains)
+        } yield results(item).map(_._1)
+        inputResults.forall(_.result.isInstanceOf[mill.api.Result.Success[_]])
+      }
 
-    val tickerPrefix = maybeTargetLabel.map { targetLabel =>
-      val prefix = s"[$counterMsg] $targetLabel "
-      if (logRun) logger.ticker(prefix)
-      prefix + "| "
-    }
+      val tickerPrefix = maybeTargetLabel.map { targetLabel =>
+        val prefix = s"[$counterMsg] $targetLabel "
+        if (logRun) logger.ticker(prefix)
+        prefix + "| "
+      }
 
-    val multiLogger = new ProxyLogger(resolveLogger(paths.map(_.log), logger)) {
-      override def ticker(s: String): Unit = {
-        super.ticker(tickerPrefix.getOrElse("") + s)
+      val multiLogger = new ProxyLogger(resolveLogger(paths.map(_.log), logger)) {
+        override def ticker(s: String): Unit = {
+          super.ticker(tickerPrefix.getOrElse("") + s)
+        }
       }
-    }
-    // This is used to track the usage of `T.dest` in more than one Task
-    // But it's not really clear what issue we try to prevent here
-    // Vice versa, being able to use T.dest in multiple `T.task`
-    // is rather essential to split up larger tasks into small parts
-    // So I like to disable this detection for now
-    var usedDest = Option.empty[(Task[_], Array[StackTraceElement])]
-    for (task <- nonEvaluatedTargets) {
-      newEvaluated.append(task)
-      val targetInputValues = task.inputs
-        .map { x => newResults.getOrElse(x, results(x)) }
-        .collect { case TaskResult(Result.Success((v, _)), _) => v }
-
-      val res =
-        if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
-        else {
-          val args = new Ctx(
-            args = targetInputValues.map(_.value).toIndexedSeq,
-            dest0 = () =>
-              paths match {
-                case Some(dest) =>
-                  if (usedDest.isEmpty) os.makeDir.all(dest.dest)
-                  usedDest = Some((task, new Exception().getStackTrace))
-                  dest.dest
-                case None =>
-                  throw new Exception("No `dest` folder available here")
-                //                }
-              },
-            log = multiLogger,
-            home = home,
-            env = env,
-            reporter = reporter,
-            testReporter = testReporter,
-            workspace = rootModule.millSourcePath
-          ) with mill.api.Ctx.Jobs {
-            override def jobs: Int = effectiveThreadCount
-          }
+      // This is used to track the usage of `T.dest` in more than one Task
+      // But it's not really clear what issue we try to prevent here
+      // Vice versa, being able to use T.dest in multiple `T.task`
+      // is rather essential to split up larger tasks into small parts
+      // So I like to disable this detection for now
+      var usedDest = Option.empty[(Task[_], Array[StackTraceElement])]
+      for (task <- nonEvaluatedTargets) {
+        newEvaluated.append(task)
+        val targetInputValues = task.inputs
+          .map { x => newResults.getOrElse(x, results(x).result) }
+          .collect { case Result.Success((v, _)) => v }
+
+        val compute = {
+          if (targetInputValues.length != task.inputs.length) () => mill.api.Result.Skipped
+          else {  () =>
+            val args = new Ctx(
+              args = targetInputValues.map(_.value).toIndexedSeq,
+              dest0 = () =>
+                paths match {
+                  case Some(dest) =>
+                    if (usedDest.isEmpty) os.makeDir.all(dest.dest)
+                    usedDest = Some((task, new Exception().getStackTrace))
+                    dest.dest
+                  case None =>
+                    throw new Exception("No `dest` folder available here")
+                  //                }
+                },
+              log = multiLogger,
+              home = home,
+              env = env,
+              reporter = reporter,
+              testReporter = testReporter,
+              workspace = rootModule.millSourcePath
+            ) with mill.api.Ctx.Jobs {
+              override def jobs: Int = effectiveThreadCount
+            }
 
-          mill.api.SystemStreams.withStreams(multiLogger.systemStreams) {
-            try task.evaluate(args).map(Val(_))
-            catch {
-              case NonFatal(e) =>
-                mill.api.Result.Exception(
-                  e,
-                  new OuterStack(new Exception().getStackTrace.toIndexedSeq)
-                )
+            mill.api.SystemStreams.withStreams(multiLogger.systemStreams) {
+              try task.evaluate(args).map(Val(_))
+              catch {
+                case NonFatal(e) =>
+                  mill.api.Result.Exception(
+                    e,
+                    new OuterStack(new Exception().getStackTrace.toIndexedSeq)
+                  )
+              }
             }
           }
         }
 
-      def makeTuple() = for (v <- res) yield {
-        (
-          v,
-          if (task.isInstanceOf[Worker[_]]) inputsHash
-          else v.##
-        )
+        newResults(task) = for (v <- compute()) yield {
+          (
+            v,
+            if (task.isInstanceOf[Worker[_]]) inputsHash
+            else v.##
+          )
+        }
       }
-      newResults(task) = TaskResult(
-        makeTuple(),
-        Option.when(task.isInstanceOf[InputImpl[_]])(() => makeTuple())
-      )
-
+      multiLogger.close()
+      (newResults, newEvaluated)
     }
 
+    val (newResults, newEvaluated) = computeAll()
+
+
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>
       val taskFailed = newResults.exists(task => !task._2.isInstanceOf[Success[_]])
       if (taskFailed) {
@@ -620,9 +623,21 @@ class Evaluator private (
       }
     }
 
-    multiLogger.close()
-
-    (newResults, newEvaluated)
+    (
+      newResults.map{case (k, v) =>
+        (
+          k,
+          TaskResult(
+            v,
+            Some{ () =>
+              val (recalced, _) = computeAll()
+              recalced.apply(k)
+            }
+          )
+        )
+      },
+      newEvaluated
+    )
   }
 
   def resolveLogger(logPath: Option[os.Path], logger: mill.api.Logger): mill.api.Logger =
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index 56382384525..f7201b07ccb 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -34,9 +34,9 @@ object RunScript {
     val watched = evaluated.results
       .iterator
       .collect {
-        case (t: SourcesImpl, TaskResult(Result.Success(Val(ps: Seq[PathRef])), None)) => ps.map(Watchable.Path(_))
-        case (t: SourceImpl, TaskResult(Result.Success(Val(p: PathRef)), None)) => Seq(Watchable.Path(p))
-        case (t: InputImpl[_], TaskResult(Result.Success(Val(v)), Some(recalc))) =>
+        case (t: SourcesImpl, TaskResult(Result.Success(Val(ps: Seq[PathRef])), _)) => ps.map(Watchable.Path(_))
+        case (t: SourceImpl, TaskResult(Result.Success(Val(p: PathRef)), _)) => Seq(Watchable.Path(p))
+        case (t: InputImpl[_], TaskResult(_, Some(recalc))) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
           Seq(Watchable.Value(() => recalc().hashCode(), recalc().hashCode(), pretty))
       }

From ad0f6f9f8db9a2d0b981558c4d607d9af3aad807 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 10:24:08 +0800
Subject: [PATCH 11/27] wip

---
 example/basic/1-simple-scala/build.sc         | 125 +++++++++++++++++-
 .../feature/watch-inputs/repo/build.sc        |  15 +++
 .../test/src/WatchInputsTests.scala           |  15 +++
 3 files changed, 150 insertions(+), 5 deletions(-)
 create mode 100644 integration/feature/watch-inputs/repo/build.sc
 create mode 100644 integration/feature/watch-inputs/test/src/WatchInputsTests.scala

diff --git a/example/basic/1-simple-scala/build.sc b/example/basic/1-simple-scala/build.sc
index e9b3366cd8b..3be43e9ade7 100644
--- a/example/basic/1-simple-scala/build.sc
+++ b/example/basic/1-simple-scala/build.sc
@@ -1,9 +1,124 @@
 
-import mill._
+import mill._, scalalib._
 
-interp.watchValue{ System.currentTimeMillis() / 5000 }
+object foo extends RootModule with ScalaModule {
+  def scalaVersion = "2.13.8"
+  def ivyDeps = Agg(
+    ivy"com.lihaoyi::scalatags:0.8.2",
+    ivy"com.lihaoyi::mainargs:0.4.0"
+  )
 
-println("Setting up build.sc")
-def foo = T.input{ System.currentTimeMillis() / 1000 }
+  object test extends Tests {
+    def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.7.11")
+    def testFramework = "utest.runner.Framework"
+  }
+}
 
-def bar = T{ foo() + " seconds since the epoch" }
+// This is a basic Mill build for a single `ScalaModule`, with two
+// third-party dependencies and a test suite using the uTest framework. As a
+// single-module project, it `extends RootModule` to mark `object foo` as the
+// top-level module in the build. This lets us directly perform operations
+// `./mill compile` or `./mill run` without needing to prefix it as
+// `foo.compile` or `foo.run`.
+//
+// You can download this example project using the *download* link above
+// if you want to try out the commands below yourself. The only requirement is
+// that you have some version of the JVM installed; the `./mill` script takes
+// care of any further dependencies that need to be downloaded.
+//
+// The source code for this module lives in the `src/` folder.
+// Output for this module (compiled files, resolved dependency lists, ...)
+// lives in `out/`.
+//
+// This example project uses two third-party dependencies - MainArgs for CLI
+// argument parsing, Scalatags for HTML generation - and uses them to wrap a
+// given input string in HTML templates with proper escaping.
+//
+// You can run `assembly` to generate a standalone executable jar, which then
+// can be run from the command line or deployed to be run elsewhere.
+
+/** Usage
+
+> ./mill resolve _ # List what tasks are available to run
+assembly
+...
+clean
+...
+compile
+...
+run
+...
+show
+...
+inspect
+...
+
+> ./mill inspect compile # Show documentation and inputs of a task
+compile(ScalaModule.scala:...)
+    Compiles the current module to generate compiled classfiles/bytecode.
+Inputs:
+    scalaVersion
+    upstreamCompileOutput
+    allSourceFiles
+    compileClasspath
+
+> ./mill compile # compile sources into classfiles
+...
+compiling 1 Scala source to...
+
+> ./mill run # run the main method, if any
+error: Missing argument: --text <str>
+
+> ./mill run --text hello
+<h1>hello</h1>
+
+> ./mill test
+...
++ foo.FooTests.simple ...  <h1>hello</h1>
++ foo.FooTests.escaping ...  <h1>&lt;hello&gt;</h1>
+
+> ./mill assembly # bundle classfiles and libraries into a jar for deployment
+
+> ./mill show assembly # show the output of the assembly task
+".../out/assembly.dest/out.jar"
+
+> java -jar ./out/assembly.dest/out.jar --text hello
+<h1>hello</h1>
+
+> ./out/assembly.dest/out.jar --text hello # mac/linux
+<h1>hello</h1>
+
+*/
+
+// The output of every Mill task is stored in the `out/` folder under a name
+// corresponding to the task that created it. e.g. The `assembly` task puts its
+// metadata output in `out/assembly.json`, and its output files in
+// `out/assembly.dest`. You can also use `show` to make Mill print out the
+// metadata output for a particular task.
+//
+// Additional Mill tasks you would likely need include:
+//
+// [source,bash]
+// ----
+// $ mill runBackground # run the main method in the background
+//
+// $ mill clean <task>  # delete the cached output of a task, terminate any runBackground
+//
+// $ mill launcher      # prepares a foo/launcher.dest/run you can run later
+//
+// $ mill jar           # bundle the classfiles into a jar suitable for publishing
+//
+// $ mill -i console    # start a Scala console within your project
+//
+// $ mill -i repl       # start an Ammonite Scala REPL within your project
+// ----
+//
+// You can run `+mill resolve __+` to see a full list of the different tasks that
+// are available, `+mill resolve _+` to see the tasks within `foo`,
+// `mill inspect compile` to inspect a task's doc-comment documentation or what
+// it depends on, or `mill show foo.scalaVersion` to show the output of any task.
+//
+// The most common *tasks* that Mill can run are cached *targets*, such as
+// `compile`, and un-cached *commands* such as `foo.run`. Targets do not
+// re-evaluate unless one of their inputs changes, whereas commands re-run every
+// time.
\ No newline at end of file
diff --git a/integration/feature/watch-inputs/repo/build.sc b/integration/feature/watch-inputs/repo/build.sc
new file mode 100644
index 00000000000..ef50bef1627
--- /dev/null
+++ b/integration/feature/watch-inputs/repo/build.sc
@@ -0,0 +1,15 @@
+
+import mill._
+
+interp.watchValue{ System.currentTimeMillis() / 5000 }
+
+println("Setting up build.sc")
+def foo = T.input{
+  println("Running foo")
+  System.currentTimeMillis() / 1000
+}
+
+def bar = T{
+  println("Running bar")
+  foo() + " seconds since the epoch"
+}
diff --git a/integration/feature/watch-inputs/test/src/WatchInputsTests.scala b/integration/feature/watch-inputs/test/src/WatchInputsTests.scala
new file mode 100644
index 00000000000..f5d7c4703f9
--- /dev/null
+++ b/integration/feature/watch-inputs/test/src/WatchInputsTests.scala
@@ -0,0 +1,15 @@
+package mill.integration
+
+import utest._
+
+object WatchInputsTests extends IntegrationTestSuite {
+  val tests = Tests {
+    initWorkspace()
+    test{
+      val t = new Thread(() => {
+        evalStdout("--watch", "bar")
+      })
+
+    }
+  }
+}

From 6f443cf47059c288533f959b16c33f02835a639d Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 12:47:20 +0800
Subject: [PATCH 12/27] WatchSourceInputTests pass

---
 .../feature/watch-inputs/repo/build.sc        |  15 --
 .../test/src/WatchInputsTests.scala           |  15 --
 .../feature/watch-source-input/repo/bar.txt   |   1 +
 .../feature/watch-source-input/repo/baz.txt   |   1 +
 .../feature/watch-source-input/repo/build.sc  |  47 ++++++
 .../feature/watch-source-input/repo/foo1.txt  |   1 +
 .../feature/watch-source-input/repo/foo2.txt  |   1 +
 .../watch-source-input/repo/watchValue.txt    |   1 +
 .../test/src/WatchSourceInputTests.scala      | 157 ++++++++++++++++++
 .../integration/IntegrationTestSuite.scala    |  27 ++-
 10 files changed, 222 insertions(+), 44 deletions(-)
 delete mode 100644 integration/feature/watch-inputs/repo/build.sc
 delete mode 100644 integration/feature/watch-inputs/test/src/WatchInputsTests.scala
 create mode 100644 integration/feature/watch-source-input/repo/bar.txt
 create mode 100644 integration/feature/watch-source-input/repo/baz.txt
 create mode 100644 integration/feature/watch-source-input/repo/build.sc
 create mode 100644 integration/feature/watch-source-input/repo/foo1.txt
 create mode 100644 integration/feature/watch-source-input/repo/foo2.txt
 create mode 100644 integration/feature/watch-source-input/repo/watchValue.txt
 create mode 100644 integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala

diff --git a/integration/feature/watch-inputs/repo/build.sc b/integration/feature/watch-inputs/repo/build.sc
deleted file mode 100644
index ef50bef1627..00000000000
--- a/integration/feature/watch-inputs/repo/build.sc
+++ /dev/null
@@ -1,15 +0,0 @@
-
-import mill._
-
-interp.watchValue{ System.currentTimeMillis() / 5000 }
-
-println("Setting up build.sc")
-def foo = T.input{
-  println("Running foo")
-  System.currentTimeMillis() / 1000
-}
-
-def bar = T{
-  println("Running bar")
-  foo() + " seconds since the epoch"
-}
diff --git a/integration/feature/watch-inputs/test/src/WatchInputsTests.scala b/integration/feature/watch-inputs/test/src/WatchInputsTests.scala
deleted file mode 100644
index f5d7c4703f9..00000000000
--- a/integration/feature/watch-inputs/test/src/WatchInputsTests.scala
+++ /dev/null
@@ -1,15 +0,0 @@
-package mill.integration
-
-import utest._
-
-object WatchInputsTests extends IntegrationTestSuite {
-  val tests = Tests {
-    initWorkspace()
-    test{
-      val t = new Thread(() => {
-        evalStdout("--watch", "bar")
-      })
-
-    }
-  }
-}
diff --git a/integration/feature/watch-source-input/repo/bar.txt b/integration/feature/watch-source-input/repo/bar.txt
new file mode 100644
index 00000000000..8634afda766
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/bar.txt
@@ -0,0 +1 @@
+initial-bar
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/repo/baz.txt b/integration/feature/watch-source-input/repo/baz.txt
new file mode 100644
index 00000000000..62fca0a765b
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/baz.txt
@@ -0,0 +1 @@
+initial-baz
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/repo/build.sc b/integration/feature/watch-source-input/repo/build.sc
new file mode 100644
index 00000000000..b033c0aecce
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/build.sc
@@ -0,0 +1,47 @@
+import mill._
+
+println("Setting up build.sc")
+
+def foo = T.sources(millSourcePath / "foo1.txt", millSourcePath / "foo2.txt")
+def bar = T.source(millSourcePath / "bar.txt")
+
+def qux = T{
+  val fooMsg = "Running qux foo contents " + foo().map(p => os.read(p.path)).mkString(" ")
+  println(fooMsg)
+
+  val barMsg = "Running qux bar contents " + os.read(bar().path)
+  println(barMsg)
+
+  writeCompletionMarker("quxRan")
+
+  fooMsg + " " + barMsg
+}
+
+interp.watchValue(PathRef(millSourcePath / "watchValue.txt"))
+
+def baz = T.input(PathRef(millSourcePath / "baz.txt"))
+
+def lol = T{
+  val barMsg = "Running lol baz contents " + os.read(baz().path)
+  println(barMsg)
+
+  writeCompletionMarker("lolRan")
+
+  barMsg
+}
+
+
+def writeCompletionMarker(name: String) = {
+
+  Range(0, 10)
+    .map(i => os.pwd / s"$name$i")
+    .find(!os.exists(_))
+    .foreach(os.write(_, ""))
+}
+
+writeCompletionMarker("initialized")
+
+if (os.read(millSourcePath / "watchValue.txt").contains("exit")){
+  Thread.sleep(1000)
+  System.exit(0)
+}
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/repo/foo1.txt b/integration/feature/watch-source-input/repo/foo1.txt
new file mode 100644
index 00000000000..acc9bce3c86
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/foo1.txt
@@ -0,0 +1 @@
+initial-foo1
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/repo/foo2.txt b/integration/feature/watch-source-input/repo/foo2.txt
new file mode 100644
index 00000000000..b9491ded04b
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/foo2.txt
@@ -0,0 +1 @@
+initial-foo2
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/repo/watchValue.txt b/integration/feature/watch-source-input/repo/watchValue.txt
new file mode 100644
index 00000000000..49e2fc36b56
--- /dev/null
+++ b/integration/feature/watch-source-input/repo/watchValue.txt
@@ -0,0 +1 @@
+initial-watchValue2
\ No newline at end of file
diff --git a/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
new file mode 100644
index 00000000000..1801fa488d0
--- /dev/null
+++ b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
@@ -0,0 +1,157 @@
+package mill.integration
+
+import utest._
+import scala.concurrent.{Await, Future}
+import scala.concurrent.duration.Duration
+import scala.concurrent.duration.SECONDS
+import scala.concurrent.ExecutionContext.Implicits.global
+
+/**
+ * Test to make sure that `--watch` works in the following cases:
+ *
+ * 1. `T.source`
+ * 2. `T.sources`
+ * 3. `T.input`
+ * 4. `interp.watchValue`
+ * 5. Implicitly watched files, like `build.sc`
+ *
+ */
+object WatchSourceInputTests extends IntegrationTestSuite {
+
+  val maxDuration = 30000
+  val tests = Tests {
+    val wsRoot = initWorkspace()
+
+    def awaitCompletionMarker(name: String) = {
+      val maxTime = System.currentTimeMillis() + maxDuration
+      while (!os.exists(wsRoot / name)) {
+        if (System.currentTimeMillis() > maxTime) {
+          sys.error(s"awaitCompletionMarker($name) timed out")
+        }
+        Thread.sleep(100)
+      }
+    }
+
+    def testWatchSource(show: Boolean) = {
+      val showArgs = if (show) Seq("show") else Nil
+
+      val evalResult = Future { evalTimeoutStdout(maxDuration, "--watch", showArgs, "qux") }
+      val expectedPrints = collection.mutable.Buffer.empty[String]
+      val expectedShows = collection.mutable.Buffer.empty[String]
+
+      awaitCompletionMarker("initialized0")
+      awaitCompletionMarker("quxRan0")
+      expectedPrints.append(
+        "Setting up build.sc",
+        "Running qux foo contents initial-foo1 initial-foo2",
+        "Running qux bar contents initial-bar"
+      )
+      expectedShows.append(
+        "Running qux foo contents initial-foo1 initial-foo2 Running qux bar contents initial-bar"
+      )
+
+      os.write.over(wsRoot / "foo1.txt", "edited-foo1")
+      awaitCompletionMarker("quxRan1")
+      expectedPrints.append(
+        "Running qux foo contents edited-foo1 initial-foo2",
+        "Running qux bar contents initial-bar",
+      )
+      expectedShows.append(
+        "Running qux foo contents edited-foo1 initial-foo2 Running qux bar contents initial-bar",
+      )
+
+      os.write.over(wsRoot / "foo2.txt", "edited-foo2")
+      awaitCompletionMarker("quxRan2")
+      expectedPrints.append(
+        "Running qux foo contents edited-foo1 edited-foo2",
+        "Running qux bar contents initial-bar",
+      )
+      expectedShows.append(
+        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents initial-bar",
+      )
+
+      os.write.over(wsRoot / "bar.txt", "edited-bar")
+      awaitCompletionMarker("quxRan3")
+      expectedPrints.append(
+        "Running qux foo contents edited-foo1 edited-foo2",
+        "Running qux bar contents edited-bar",
+      )
+      expectedShows.append(
+        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents edited-bar",
+      )
+
+      os.write.append(wsRoot / "build.sc", "\ndef unrelated = true")
+      awaitCompletionMarker("initialized1")
+      expectedPrints.append(
+        "Setting up build.sc",
+        "Running qux foo contents edited-foo1 edited-foo2",
+        "Running qux bar contents edited-bar",
+      )
+      expectedShows.append(
+        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents edited-bar"
+      )
+
+      os.write.over(wsRoot / "watchValue.txt", "exit")
+      awaitCompletionMarker("initialized2")
+      expectedPrints.append("Setting up build.sc")
+
+      val res = Await.result(evalResult, Duration.apply(maxDuration, SECONDS))
+
+
+
+      val (shows, prints) = res.out.linesIterator.toVector.partition(_.startsWith("\""))
+
+      assert(prints == expectedPrints)
+      if (show) assert(shows == expectedShows.map('"' + _ + '"'))
+    }
+
+    test("sources"){
+
+      test("noshow") - testWatchSource(false)
+      test("show") - testWatchSource(true)
+    }
+
+    def testWatchInput(show: Boolean) = {
+      val showArgs = if (show) Seq("show") else Nil
+
+      val evalResult = Future{ evalTimeoutStdout(maxDuration, "--watch", showArgs, "lol") }
+      val expectedPrints = collection.mutable.Buffer.empty[String]
+      val expectedShows = collection.mutable.Buffer.empty[String]
+
+      awaitCompletionMarker("initialized0")
+      awaitCompletionMarker("lolRan0")
+      expectedPrints.append(
+        "Setting up build.sc",
+        "Running lol baz contents initial-baz",
+      )
+      expectedShows.append("Running lol baz contents initial-baz")
+
+      os.write.over(wsRoot / "baz.txt", "edited-baz")
+      awaitCompletionMarker("lolRan1")
+      expectedPrints.append("Running lol baz contents edited-baz")
+      expectedShows.append("Running lol baz contents edited-baz")
+
+      os.write.over(wsRoot / "watchValue.txt", "edited-watchValue")
+      awaitCompletionMarker("initialized1")
+      expectedPrints.append("Setting up build.sc")
+      expectedShows.append("Running lol baz contents edited-baz")
+
+      os.write.over(wsRoot / "watchValue.txt", "exit")
+      awaitCompletionMarker("initialized2")
+      expectedPrints.append("Setting up build.sc")
+
+      val res = Await.result(evalResult, Duration.apply(maxDuration, SECONDS))
+
+
+      val (shows, prints) = res.out.linesIterator.toVector.partition(_.startsWith("\""))
+      assert(prints == expectedPrints)
+      if (show) assert(shows == expectedShows.map('"' + _ + '"'))
+    }
+
+    test("input"){
+
+      test("noshow") - testWatchInput(false)
+      test("show") - testWatchInput(true)
+    }
+  }
+}
diff --git a/integration/src/mill/integration/IntegrationTestSuite.scala b/integration/src/mill/integration/IntegrationTestSuite.scala
index e59e275e44d..b8f32182831 100644
--- a/integration/src/mill/integration/IntegrationTestSuite.scala
+++ b/integration/src/mill/integration/IntegrationTestSuite.scala
@@ -1,21 +1,14 @@
 package mill.integration
 
-import mainargs.Flag
-import mill.runner.MillCliConfig
 import mill.main.SelectMode
-import mill.runner.{MillBuildBootstrap, MillMain, RunnerState, Watching}
-import mill.api.SystemStreams
-import mill.util.PrintLogger
-import os.Path
+import mill.runner.RunnerState
+import os.{Path, Shellable}
 import utest._
 
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream, PrintStream}
-import java.nio.file.NoSuchFileException
 import scala.util.control.NonFatal
 
 object IntegrationTestSuite {
   case class EvalResult(isSuccess: Boolean, out: String, err: String)
-
 }
 
 abstract class IntegrationTestSuite extends TestSuite {
@@ -37,16 +30,20 @@ abstract class IntegrationTestSuite extends TestSuite {
 
   var runnerState = RunnerState.empty
 
-  def eval(s: String*): Boolean = evalFork(os.Inherit, os.Inherit, s)
+  def eval(s: Shellable*): Boolean = evalFork(os.Inherit, os.Inherit, s, -1)
+
+  def evalStdout(s: Shellable*): IntegrationTestSuite.EvalResult = {
+    evalTimeoutStdout(-1, s:_*)
+  }
 
-  def evalStdout(s: String*): IntegrationTestSuite.EvalResult = {
+  def evalTimeoutStdout(timeout: Long, s: Shellable*): IntegrationTestSuite.EvalResult = {
 
     val output = Seq.newBuilder[String]
     val error = Seq.newBuilder[String]
     val processOutput = os.ProcessOutput.Readlines(output += _)
     val processError = os.ProcessOutput.Readlines(error += _)
 
-    val result = evalFork(processOutput, processError, s)
+    val result = evalFork(processOutput, processError, s, timeout)
     IntegrationTestSuite.EvalResult(
       result,
       output.result().mkString("\n"),
@@ -61,7 +58,8 @@ abstract class IntegrationTestSuite extends TestSuite {
   private def evalFork(
       stdout: os.ProcessOutput,
       stderr: os.ProcessOutput,
-      s: Seq[String]
+      s: Seq[Shellable],
+      timeout: Long
   ): Boolean = {
     val serverArgs =
       if (integrationTestMode == "server" || integrationTestMode == "local") Seq()
@@ -75,7 +73,8 @@ abstract class IntegrationTestSuite extends TestSuite {
         stdin = os.Inherit,
         stdout = stdout,
         stderr = stderr,
-        env = millTestSuiteEnv
+        env = millTestSuiteEnv,
+        timeout = timeout
       )
       true
     } catch {

From 1e3e92d4a4f21978f49160baae683c3680a8339c Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 13:10:13 +0800
Subject: [PATCH 13/27] wip

---
 .../mill/integration/ExampleTestSuite.scala   |  2 +-
 .../test/src/WatchSourceInputTests.scala      | 26 ++++------
 .../integration/IntegrationTestSuite.scala    |  2 +-
 main/api/src/mill/api/Val.scala               | 10 ++++
 main/eval/src/mill/eval/Evaluator.scala       | 51 ++++++++++---------
 main/src/mill/main/MainModule.scala           | 16 +++---
 main/src/mill/main/RunScript.scala            | 15 ++++--
 main/src/mill/main/VisualizeModule.scala      |  2 +-
 main/test/src/mill/main/MainModuleTests.scala | 14 ++---
 .../src/mill/runner/MillBuildBootstrap.scala  | 15 +++---
 runner/src/mill/runner/RunnerState.scala      |  5 +-
 11 files changed, 86 insertions(+), 72 deletions(-)
 create mode 100644 main/api/src/mill/api/Val.scala

diff --git a/example/src/mill/integration/ExampleTestSuite.scala b/example/src/mill/integration/ExampleTestSuite.scala
index cd068300fc8..15d996f1a84 100644
--- a/example/src/mill/integration/ExampleTestSuite.scala
+++ b/example/src/mill/integration/ExampleTestSuite.scala
@@ -88,7 +88,7 @@ object ExampleTestSuite extends IntegrationTestSuite {
     BashTokenizer.tokenize(commandStr) match {
       case Seq(s"./$command", rest @ _*) =>
         val evalResult = command match {
-          case "mill" => evalStdout(rest: _*)
+          case "mill" => evalStdout(rest)
           case cmd =>
             val tokens = cmd +: rest
             val executable = workspaceRoot / os.RelPath(tokens.head)
diff --git a/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
index 1801fa488d0..38b8f0ca221 100644
--- a/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
+++ b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
@@ -14,7 +14,6 @@ import scala.concurrent.ExecutionContext.Implicits.global
  * 3. `T.input`
  * 4. `interp.watchValue`
  * 5. Implicitly watched files, like `build.sc`
- *
  */
 object WatchSourceInputTests extends IntegrationTestSuite {
 
@@ -54,30 +53,30 @@ object WatchSourceInputTests extends IntegrationTestSuite {
       awaitCompletionMarker("quxRan1")
       expectedPrints.append(
         "Running qux foo contents edited-foo1 initial-foo2",
-        "Running qux bar contents initial-bar",
+        "Running qux bar contents initial-bar"
       )
       expectedShows.append(
-        "Running qux foo contents edited-foo1 initial-foo2 Running qux bar contents initial-bar",
+        "Running qux foo contents edited-foo1 initial-foo2 Running qux bar contents initial-bar"
       )
 
       os.write.over(wsRoot / "foo2.txt", "edited-foo2")
       awaitCompletionMarker("quxRan2")
       expectedPrints.append(
         "Running qux foo contents edited-foo1 edited-foo2",
-        "Running qux bar contents initial-bar",
+        "Running qux bar contents initial-bar"
       )
       expectedShows.append(
-        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents initial-bar",
+        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents initial-bar"
       )
 
       os.write.over(wsRoot / "bar.txt", "edited-bar")
       awaitCompletionMarker("quxRan3")
       expectedPrints.append(
         "Running qux foo contents edited-foo1 edited-foo2",
-        "Running qux bar contents edited-bar",
+        "Running qux bar contents edited-bar"
       )
       expectedShows.append(
-        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents edited-bar",
+        "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents edited-bar"
       )
 
       os.write.append(wsRoot / "build.sc", "\ndef unrelated = true")
@@ -85,7 +84,7 @@ object WatchSourceInputTests extends IntegrationTestSuite {
       expectedPrints.append(
         "Setting up build.sc",
         "Running qux foo contents edited-foo1 edited-foo2",
-        "Running qux bar contents edited-bar",
+        "Running qux bar contents edited-bar"
       )
       expectedShows.append(
         "Running qux foo contents edited-foo1 edited-foo2 Running qux bar contents edited-bar"
@@ -97,15 +96,13 @@ object WatchSourceInputTests extends IntegrationTestSuite {
 
       val res = Await.result(evalResult, Duration.apply(maxDuration, SECONDS))
 
-
-
       val (shows, prints) = res.out.linesIterator.toVector.partition(_.startsWith("\""))
 
       assert(prints == expectedPrints)
       if (show) assert(shows == expectedShows.map('"' + _ + '"'))
     }
 
-    test("sources"){
+    test("sources") {
 
       test("noshow") - testWatchSource(false)
       test("show") - testWatchSource(true)
@@ -114,7 +111,7 @@ object WatchSourceInputTests extends IntegrationTestSuite {
     def testWatchInput(show: Boolean) = {
       val showArgs = if (show) Seq("show") else Nil
 
-      val evalResult = Future{ evalTimeoutStdout(maxDuration, "--watch", showArgs, "lol") }
+      val evalResult = Future { evalTimeoutStdout(maxDuration, "--watch", showArgs, "lol") }
       val expectedPrints = collection.mutable.Buffer.empty[String]
       val expectedShows = collection.mutable.Buffer.empty[String]
 
@@ -122,7 +119,7 @@ object WatchSourceInputTests extends IntegrationTestSuite {
       awaitCompletionMarker("lolRan0")
       expectedPrints.append(
         "Setting up build.sc",
-        "Running lol baz contents initial-baz",
+        "Running lol baz contents initial-baz"
       )
       expectedShows.append("Running lol baz contents initial-baz")
 
@@ -142,13 +139,12 @@ object WatchSourceInputTests extends IntegrationTestSuite {
 
       val res = Await.result(evalResult, Duration.apply(maxDuration, SECONDS))
 
-
       val (shows, prints) = res.out.linesIterator.toVector.partition(_.startsWith("\""))
       assert(prints == expectedPrints)
       if (show) assert(shows == expectedShows.map('"' + _ + '"'))
     }
 
-    test("input"){
+    test("input") {
 
       test("noshow") - testWatchInput(false)
       test("show") - testWatchInput(true)
diff --git a/integration/src/mill/integration/IntegrationTestSuite.scala b/integration/src/mill/integration/IntegrationTestSuite.scala
index b8f32182831..75086dd1b15 100644
--- a/integration/src/mill/integration/IntegrationTestSuite.scala
+++ b/integration/src/mill/integration/IntegrationTestSuite.scala
@@ -33,7 +33,7 @@ abstract class IntegrationTestSuite extends TestSuite {
   def eval(s: Shellable*): Boolean = evalFork(os.Inherit, os.Inherit, s, -1)
 
   def evalStdout(s: Shellable*): IntegrationTestSuite.EvalResult = {
-    evalTimeoutStdout(-1, s:_*)
+    evalTimeoutStdout(-1, s: _*)
   }
 
   def evalTimeoutStdout(timeout: Long, s: Shellable*): IntegrationTestSuite.EvalResult = {
diff --git a/main/api/src/mill/api/Val.scala b/main/api/src/mill/api/Val.scala
new file mode 100644
index 00000000000..e80d92b393d
--- /dev/null
+++ b/main/api/src/mill/api/Val.scala
@@ -0,0 +1,10 @@
+package mill.api
+
+/**
+ * A somewhat-type-safe wrapper around `Any`. Stores an un-typed value, but
+ * can only be created explicitly by wrapping in `Val(_)` and de-constructed
+ * explicitly via `.value`. That makes it much less likely to introduce bugs
+ * passing the wrong thing, e.g. `(Any, Int)` can be passed to `Any`, but
+ * `(Val, Int)` cannot be passed to `Val`
+ */
+case class Val(value: Any)
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 5f9b14dff3d..0ffefc46cef 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -10,7 +10,8 @@ import mill.api.{
   PathRef,
   Result,
   Strict,
-  TestReporter
+  TestReporter,
+  Val
 }
 import mill.api.Result.{Aborted, Failing, OuterStack, Success}
 import mill.api.Strict.Agg
@@ -35,7 +36,7 @@ class Evaluator private (
     _rootModule: mill.define.BaseModule,
     _baseLogger: ColorLogger,
     _classLoaderSigHash: Int,
-    _workerCache: mutable.Map[Segments, (Int, Any)],
+    _workerCache: mutable.Map[Segments, (Int, Val)],
     _env: Map[String, String],
     _failFast: Boolean,
     _threadCount: Option[Int],
@@ -65,7 +66,7 @@ class Evaluator private (
   /**
    * Mutable worker cache.
    */
-  def workerCache: mutable.Map[Segments, (Int, Any)] = _workerCache
+  def workerCache: mutable.Map[Segments, (Int, Val)] = _workerCache
   def env: Map[String, String] = _env
 
   /**
@@ -184,8 +185,9 @@ class Evaluator private (
       failing.addAll(
         k,
         Loose.Agg.from(
-          vs.items.flatMap(results.get).collect { case er @ TaskResult(f: mill.api.Result.Failing[_], _) =>
-            f
+          vs.items.flatMap(results.get).collect {
+            case er @ TaskResult(f: mill.api.Result.Failing[_], _) =>
+              f
           }
         )
       )
@@ -255,7 +257,8 @@ class Evaluator private (
               contextLogger
             )
 
-            if (failFast && res.newResults.values.exists(_.result.asSuccess.isEmpty)) failed.set(true)
+            if (failFast && res.newResults.values.exists(_.result.asSuccess.isEmpty))
+              failed.set(true)
 
             val endTime = System.currentTimeMillis()
             timeLog.timeTrace(
@@ -292,7 +295,7 @@ class Evaluator private (
       timeLog.close()
 
       Evaluator.Results(
-        goals.indexed.map(results(_).map(_._1)),
+        goals.indexed.map(results(_).map(_._1).result),
         finishedOpts.map(_._2).flatMap(_.toSeq.flatMap(_.newEvaluated)),
         transitive,
         getFailing(sortedGroups, results),
@@ -375,7 +378,7 @@ class Evaluator private (
           destSegments(labelledNamedTask)
         )
 
-        val cached: Option[(Any, Int)] = for {
+        val cached: Option[(Val, Int)] = for {
           cached <-
             try Some(upickle.default.read[Evaluator.Cached](paths.meta.toIO))
             catch {
@@ -393,12 +396,12 @@ class Evaluator private (
                 None
               case NonFatal(_) => None
             }
-        } yield (parsed, cached.valueHash)
+        } yield (Val(parsed), cached.valueHash)
 
         val previousWorker = labelledNamedTask.task.asWorker.flatMap { w =>
           workerCache.synchronized { workerCache.get(w.ctx.segments) }
         }
-        val upToDateWorker: Option[Any] = previousWorker.flatMap {
+        val upToDateWorker: Option[Val] = previousWorker.flatMap {
           case (`inputsHash`, upToDate) =>
             // worker cached and up-to-date
             Some(upToDate)
@@ -426,7 +429,7 @@ class Evaluator private (
         upToDateWorker.map((_, inputsHash)) orElse cached match {
           case Some((v, hashCode)) =>
             val newResults = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
-            newResults(labelledNamedTask.task) = TaskResult(Result.Success((Val(v), hashCode)), None)
+            newResults(labelledNamedTask.task) = TaskResult(Result.Success((v, hashCode)), None)
 
             Evaluated(newResults, Nil, cached = true)
 
@@ -491,14 +494,14 @@ class Evaluator private (
     labelledNamedTask.task.asWorker match {
       case Some(w) =>
         workerCache.synchronized {
-          workerCache.update(w.ctx.segments, (inputsHash, v.value))
+          workerCache.update(w.ctx.segments, (inputsHash, v))
         }
       case None =>
         val terminalResult = labelledNamedTask
           .task
           .writerOpt
           .asInstanceOf[Option[upickle.default.Writer[Any]]]
-          .map{w => upickle.default.writeJs(v.value)(w)}
+          .map { w => upickle.default.writeJs(v.value)(w) }
 
         for (json <- terminalResult) {
           os.write.over(
@@ -565,7 +568,7 @@ class Evaluator private (
 
         val compute = {
           if (targetInputValues.length != task.inputs.length) () => mill.api.Result.Skipped
-          else {  () =>
+          else { () =>
             val args = new Ctx(
               args = targetInputValues.map(_.value).toIndexedSeq,
               dest0 = () =>
@@ -615,7 +618,6 @@ class Evaluator private (
 
     val (newResults, newEvaluated) = computeAll()
 
-
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>
       val taskFailed = newResults.exists(task => !task._2.isInstanceOf[Success[_]])
       if (taskFailed) {
@@ -624,12 +626,12 @@ class Evaluator private (
     }
 
     (
-      newResults.map{case (k, v) =>
+      newResults.map { case (k, v) =>
         (
           k,
           TaskResult(
             v,
-            Some{ () =>
+            Some { () =>
               val (recalced, _) = computeAll()
               recalced.apply(k)
             }
@@ -704,7 +706,7 @@ class Evaluator private (
       rootModule: mill.define.BaseModule = this.rootModule,
       baseLogger: ColorLogger = this.baseLogger,
       classLoaderSigHash: Int = this.classLoaderSigHash,
-      workerCache: mutable.Map[Segments, (Int, Any)] = this.workerCache,
+      workerCache: mutable.Map[Segments, (Int, Val)] = this.workerCache,
       env: Map[String, String] = this.env,
       failFast: Boolean = this.failFast,
       threadCount: Option[Int] = this.threadCount,
@@ -731,7 +733,7 @@ class Evaluator private (
     copy(rootModule = rootModule)
   def withBaseLogger(baseLogger: ColorLogger): Evaluator = copy(baseLogger = baseLogger)
 
-  def withWorkerCache(workerCache: mutable.Map[Segments, (Int, Any)]): Evaluator =
+  def withWorkerCache(workerCache: mutable.Map[Segments, (Int, Val)]): Evaluator =
     copy(workerCache = workerCache)
   def withEnv(env: Map[String, String]): Evaluator = copy(env = env)
   def withFailFast(failFast: Boolean): Evaluator = copy(failFast = failFast)
@@ -783,16 +785,15 @@ object Evaluator {
     )
   }
 
-  case class TaskResult[T](result: Result[T],
-                           recalcOpt: Option[() => mill.api.Result[T]]){
+  case class TaskResult[T](result: Result[T], recalcOpt: Option[() => mill.api.Result[T]]) {
     def map[V](f: T => V) = TaskResult[V](
       result.map(f),
       recalcOpt.map(r => () => r().map(f))
     )
   }
-  case class Val(value: Any)
+
   case class Results(
-      rawValues: Seq[mill.api.Result[Any]],
+      rawValues: Seq[mill.api.Result[Val]],
       evaluated: Agg[Task[_]],
       transitive: Agg[Task[_]],
       failing: MultiBiMap[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]],
@@ -800,7 +801,7 @@ object Evaluator {
   ) {
     def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v) => v }
     private def copy(
-        rawValues: Seq[Result[Any]] = rawValues,
+        rawValues: Seq[Result[Val]] = rawValues,
         evaluated: Agg[Task[_]] = evaluated,
         transitive: Agg[Task[_]] = transitive,
         failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[_]] = failing,
@@ -820,7 +821,7 @@ object Evaluator {
         Agg[Task[_]],
         Agg[Task[_]],
         MultiBiMap[Either[Task[_], Labelled[_]], Failing[_]],
-          collection.Map[Task[_], TaskResult[_]]
+        collection.Map[Task[_], TaskResult[_]]
     )] = Some((
       results.rawValues,
       results.evaluated,
diff --git a/main/src/mill/main/MainModule.scala b/main/src/mill/main/MainModule.scala
index d59e23a83ab..ba6116b9cb6 100644
--- a/main/src/mill/main/MainModule.scala
+++ b/main/src/mill/main/MainModule.scala
@@ -26,11 +26,12 @@ object MainModule {
     }
   }
 
-  private def show0(evaluator: Evaluator,
-                    targets: Seq[String],
-                    log: Logger,
-                    watch0: Watchable => Unit)
-                   (f: Seq[(Any, Option[(RunScript.TaskName, ujson.Value)])] => ujson.Value) = {
+  private def show0(
+      evaluator: Evaluator,
+      targets: Seq[String],
+      log: Logger,
+      watch0: Watchable => Unit
+  )(f: Seq[(Any, Option[(RunScript.TaskName, ujson.Value)])] => ujson.Value) = {
     RunScript.evaluateTasksNamed(
       evaluator.withBaseLogger(
         // When using `show`, redirect all stdout of the evaluated tasks so the
@@ -93,7 +94,6 @@ trait MainModule extends mill.Module {
     }
   }
 
-
   implicit def millDiscover: mill.define.Discover[_]
 
   /**
@@ -279,8 +279,8 @@ trait MainModule extends mill.Module {
    * to integrate Mill into external scripts and tooling.
    */
   def show(evaluator: Evaluator, targets: String*): Command[ujson.Value] = T.command {
-    MainModule.show0(evaluator, targets, T.log, interp.evalWatch0){ res =>
-      res.flatMap(_._2).map(_._2) match{
+    MainModule.show0(evaluator, targets, T.log, interp.evalWatch0) { res =>
+      res.flatMap(_._2).map(_._2) match {
         case Seq(single) => single
         case multiple => multiple
       }
diff --git a/main/src/mill/main/RunScript.scala b/main/src/mill/main/RunScript.scala
index f7201b07ccb..713012cb224 100644
--- a/main/src/mill/main/RunScript.scala
+++ b/main/src/mill/main/RunScript.scala
@@ -3,7 +3,7 @@ package mill.main
 import mill.define._
 import mill.eval.{Evaluator, EvaluatorPaths}
 import mill.util.Watchable
-import mill.api.{PathRef, Result}
+import mill.api.{PathRef, Result, Val}
 import mill.api.Strict.Agg
 import Evaluator._
 
@@ -15,9 +15,12 @@ object RunScript {
       evaluator: Evaluator,
       scriptArgs: Seq[String],
       selectMode: SelectMode
-  ): Either[String, (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])] = {
+  ): Either[
+    String,
+    (Seq[Watchable], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])
+  ] = {
     for (targets <- ResolveTasks.resolve(evaluator, scriptArgs, selectMode))
-    yield evaluateNamed(evaluator, Agg.from(targets.distinct))
+      yield evaluateNamed(evaluator, Agg.from(targets.distinct))
   }
 
   /**
@@ -34,8 +37,10 @@ object RunScript {
     val watched = evaluated.results
       .iterator
       .collect {
-        case (t: SourcesImpl, TaskResult(Result.Success(Val(ps: Seq[PathRef])), _)) => ps.map(Watchable.Path(_))
-        case (t: SourceImpl, TaskResult(Result.Success(Val(p: PathRef)), _)) => Seq(Watchable.Path(p))
+        case (t: SourcesImpl, TaskResult(Result.Success(Val(ps: Seq[PathRef])), _)) =>
+          ps.map(Watchable.Path(_))
+        case (t: SourceImpl, TaskResult(Result.Success(Val(p: PathRef)), _)) =>
+          Seq(Watchable.Path(p))
         case (t: InputImpl[_], TaskResult(_, Some(recalc))) =>
           val pretty = t.ctx0.fileName + ":" + t.ctx0.lineNum
           Seq(Watchable.Value(() => recalc().hashCode(), recalc().hashCode(), pretty))
diff --git a/main/src/mill/main/VisualizeModule.scala b/main/src/mill/main/VisualizeModule.scala
index fa13cbe2927..e4309949db5 100644
--- a/main/src/mill/main/VisualizeModule.scala
+++ b/main/src/mill/main/VisualizeModule.scala
@@ -42,7 +42,7 @@ trait VisualizeModule extends mill.define.TaskModule {
     )
     val visualizeThread = new java.lang.Thread(() =>
       while (true) {
-        val res = Result.Success{
+        val res = Result.Success {
           val (targets, tasks, dest) = in.take()
           cl.loadClass("mill.main.graphviz.GraphvizTools")
             .getMethod("apply", classOf[Seq[_]], classOf[Seq[_]], classOf[os.Path])
diff --git a/main/test/src/mill/main/MainModuleTests.scala b/main/test/src/mill/main/MainModuleTests.scala
index aca9b114add..9a4115fcafa 100644
--- a/main/test/src/mill/main/MainModuleTests.scala
+++ b/main/test/src/mill/main/MainModuleTests.scala
@@ -1,6 +1,6 @@
 package mill.main
 
-import mill.api.{PathRef, Result}
+import mill.api.{PathRef, Result, Val}
 import mill.{Agg, T}
 import mill.define.{Cross, Module}
 import mill.util.{TestEvaluator, TestUtil}
@@ -49,7 +49,7 @@ object MainModuleTests extends TestSuite {
       val eval = new TestEvaluator(mainModule)
       test("single") {
         val res = eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello")))
-        val Result.Success(value: String) = res.rawValues.head
+        val Result.Success(Val(value: String)) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -59,7 +59,7 @@ object MainModuleTests extends TestSuite {
       test("multi") {
         val res =
           eval.evaluator.evaluate(Agg(mainModule.inspect(eval.evaluator, "hello", "hello2")))
-        val Result.Success(value: String) = res.rawValues.head
+        val Result.Success(Val(value: String)) = res.rawValues.head
         assert(
           res.failing.keyCount == 0,
           value.startsWith("hello("),
@@ -77,7 +77,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(Val(value)) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq("hello", "world")))
       }
@@ -92,7 +92,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(Val(value)) = results.rawValues.head
 
         assert(value == ujson.Arr.from(Seq(
           ujson.Arr.from(Seq("hello", "world")),
@@ -109,7 +109,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(Val(value)) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world"))
@@ -126,7 +126,7 @@ object MainModuleTests extends TestSuite {
 
         assert(results.failing.keyCount == 0)
 
-        val Result.Success(value) = results.rawValues.head
+        val Result.Success(Val(value)) = results.rawValues.head
 
         assert(value == ujson.Obj.from(Map(
           "hello" -> ujson.Arr.from(Seq("hello", "world")),
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index 36455e6b3c2..0b09606e8e3 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -1,9 +1,8 @@
 package mill.runner
 import mill.util.{ColorLogger, PrefixLogger, Util, Watchable}
 import mill.{BuildInfo, T}
-import mill.api.{PathRef, internal}
+import mill.api.{PathRef, Val, internal}
 import mill.eval.Evaluator
-
 import mill.main.{RootModule, RunScript, SelectMode}
 import mill.main.TokenReaders._
 import mill.define.{Discover, Segments}
@@ -194,8 +193,8 @@ class MillBuildBootstrap(
 
       case (
             Right(Seq(
-              Evaluator.Val(runClasspath: Seq[PathRef]),
-              Evaluator.Val(scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])])
+              Val(runClasspath: Seq[PathRef]),
+              Val(scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])])
             )),
             evalWatches,
             moduleWatches
@@ -268,7 +267,7 @@ class MillBuildBootstrap(
   }
 
   def makeEvaluator(
-      workerCache: Map[Segments, (Int, Any)],
+      workerCache: Map[Segments, (Int, Val)],
       scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])],
       rootModule: RootModule,
       millClassloaderSigHash: Int,
@@ -334,7 +333,8 @@ object MillBuildBootstrap {
       targetsAndParams: Seq[String]
   ): (Either[String, Seq[Any]], Seq[Watchable], Seq[Watchable]) = {
     rootModule.evalWatchedValues.clear()
-    val evalTaskResult = RunScript.evaluateTasksNamed(evaluator, targetsAndParams, SelectMode.Separated)
+    val evalTaskResult =
+      RunScript.evaluateTasksNamed(evaluator, targetsAndParams, SelectMode.Separated)
     val moduleWatched = rootModule.watchedValues.toVector
     val addedEvalWatched = rootModule.evalWatchedValues.toVector
 
@@ -343,7 +343,8 @@ object MillBuildBootstrap {
       case Right((watched, evaluated)) =>
         evaluated match {
           case Left(msg) => (Left(msg), watched ++ addedEvalWatched, moduleWatched)
-          case Right(results) => (Right(results.map(_._1)), watched ++ addedEvalWatched, moduleWatched)
+          case Right(results) =>
+            (Right(results.map(_._1)), watched ++ addedEvalWatched, moduleWatched)
         }
     }
   }
diff --git a/runner/src/mill/runner/RunnerState.scala b/runner/src/mill/runner/RunnerState.scala
index c7b05545661..399d8c20fa5 100644
--- a/runner/src/mill/runner/RunnerState.scala
+++ b/runner/src/mill/runner/RunnerState.scala
@@ -1,10 +1,11 @@
 package mill.runner
 
-import mill.api.{PathRef, internal}
+import mill.api.{PathRef, Val, internal}
 import mill.define.{BaseModule, Segments}
 import mill.util.Watchable
 import upickle.default.{ReadWriter, macroRW}
 import mill.api.JsonFormatters._
+import mill.eval.Evaluator
 import mill.main.RootModule
 
 /**
@@ -51,7 +52,7 @@ object RunnerState {
 
   @internal
   case class Frame(
-      workerCache: Map[Segments, (Int, Any)],
+      workerCache: Map[Segments, (Int, Val)],
       evalWatched: Seq[Watchable],
       moduleWatched: Seq[Watchable],
       scriptImportGraph: Map[os.Path, (Int, Seq[os.Path])],

From 2d79417e6dbec889886a78e49fbf8f208ea13ef9 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 13:38:34 +0800
Subject: [PATCH 14/27] pass

---
 example/tasks/2-primary-tasks/src/Foo.java      |  2 --
 .../feature/watch-source-input/repo/build.sc    |  2 +-
 .../test/src/WatchSourceInputTests.scala        |  2 +-
 main/eval/src/mill/eval/Evaluator.scala         | 17 +++++++++--------
 .../src/mill/runner/MillBuildRootModule.scala   | 10 +++++-----
 5 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/example/tasks/2-primary-tasks/src/Foo.java b/example/tasks/2-primary-tasks/src/Foo.java
index 0c688a3e9ec..7f6eaa4135a 100644
--- a/example/tasks/2-primary-tasks/src/Foo.java
+++ b/example/tasks/2-primary-tasks/src/Foo.java
@@ -13,6 +13,4 @@ public static void main(String[] args) throws IOException{
             System.out.println("foo.txt resource: " + br.readLine());
         }
     }
-
-
 }
diff --git a/integration/feature/watch-source-input/repo/build.sc b/integration/feature/watch-source-input/repo/build.sc
index b033c0aecce..70bf339d6c2 100644
--- a/integration/feature/watch-source-input/repo/build.sc
+++ b/integration/feature/watch-source-input/repo/build.sc
@@ -34,7 +34,7 @@ def lol = T{
 def writeCompletionMarker(name: String) = {
 
   Range(0, 10)
-    .map(i => os.pwd / s"$name$i")
+    .map(i => os.pwd / "out" / s"$name$i")
     .find(!os.exists(_))
     .foreach(os.write(_, ""))
 }
diff --git a/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
index 38b8f0ca221..c2f869007c0 100644
--- a/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
+++ b/integration/feature/watch-source-input/test/src/WatchSourceInputTests.scala
@@ -23,7 +23,7 @@ object WatchSourceInputTests extends IntegrationTestSuite {
 
     def awaitCompletionMarker(name: String) = {
       val maxTime = System.currentTimeMillis() + maxDuration
-      while (!os.exists(wsRoot / name)) {
+      while (!os.exists(wsRoot / "out" / name)) {
         if (System.currentTimeMillis() > maxTime) {
           sys.error(s"awaitCompletionMarker($name) timed out")
         }
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 0ffefc46cef..865c64e8b9c 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -528,7 +528,7 @@ class Evaluator private (
       logger: mill.api.Logger
   ): (mutable.LinkedHashMap[Task[_], TaskResult[(Val, Int)]], mutable.Buffer[Task[_]]) = {
 
-    def computeAll() = {
+    def computeAll(enableTicker: Boolean) = {
       val newEvaluated = mutable.Buffer.empty[Task[_]]
       val newResults = mutable.LinkedHashMap.empty[Task[_], Result[(Val, Int)]]
 
@@ -551,7 +551,8 @@ class Evaluator private (
 
       val multiLogger = new ProxyLogger(resolveLogger(paths.map(_.log), logger)) {
         override def ticker(s: String): Unit = {
-          super.ticker(tickerPrefix.getOrElse("") + s)
+          if (enableTicker) super.ticker(tickerPrefix.getOrElse("") + s)
+          else () // do nothing
         }
       }
       // This is used to track the usage of `T.dest` in more than one Task
@@ -566,9 +567,9 @@ class Evaluator private (
           .map { x => newResults.getOrElse(x, results(x).result) }
           .collect { case Result.Success((v, _)) => v }
 
-        val compute = {
-          if (targetInputValues.length != task.inputs.length) () => mill.api.Result.Skipped
-          else { () =>
+        val res = {
+          if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
+          else {
             val args = new Ctx(
               args = targetInputValues.map(_.value).toIndexedSeq,
               dest0 = () =>
@@ -604,7 +605,7 @@ class Evaluator private (
           }
         }
 
-        newResults(task) = for (v <- compute()) yield {
+        newResults(task) = for (v <- res) yield {
           (
             v,
             if (task.isInstanceOf[Worker[_]]) inputsHash
@@ -616,7 +617,7 @@ class Evaluator private (
       (newResults, newEvaluated)
     }
 
-    val (newResults, newEvaluated) = computeAll()
+    val (newResults, newEvaluated) = computeAll(enableTicker = true)
 
     if (!failFast) maybeTargetLabel.foreach { targetLabel =>
       val taskFailed = newResults.exists(task => !task._2.isInstanceOf[Success[_]])
@@ -632,7 +633,7 @@ class Evaluator private (
           TaskResult(
             v,
             Some { () =>
-              val (recalced, _) = computeAll()
+              val (recalced, _) = computeAll(enableTicker = false)
               recalced.apply(k)
             }
           )
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 4c321a73fb1..62698df9c0a 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -129,11 +129,11 @@ class MillBuildRootModule()(implicit
     Lib.findSourceFiles(allSources(), Seq("scala", "java", "sc")).map(PathRef(_))
   }
 
-  override def unmanagedClasspath: T[Agg[PathRef]] = mill.define.Target.input {
-    mill.api.Loose.Agg.from(
-      millBuildRootModule.enclosingClasspath.map(p => mill.api.PathRef(p, quick = true))
-    ) ++
-      lineNumberPluginClasspath()
+  def enclosingClasspath = T.sources {
+    millBuildRootModule.enclosingClasspath.map(p => mill.api.PathRef(p, quick = true))
+  }
+  override def unmanagedClasspath: T[Agg[PathRef]] = T{
+    enclosingClasspath() ++ lineNumberPluginClasspath()
   }
 
   override def scalacPluginIvyDeps = Agg(

From 1a69380a918fd92c18b3771acc772af23a519439 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 14:32:25 +0800
Subject: [PATCH 15/27] .

---
 .../src/mill/runner/MillBuildRootModule.scala | 28 ++++++++++++++-----
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 62698df9c0a..7936ebd7eb3 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -27,7 +27,7 @@ import scala.util.Try
 @internal
 class MillBuildRootModule()(implicit
     baseModuleInfo: RootModule.Info,
-    millBuildRootModule: MillBuildRootModule.Info
+    millBuildRootModuleInfo: MillBuildRootModule.Info
 ) extends RootModule() with ScalaModule {
 
   override def millSourcePath = millBuildRootModule.projectRoot / os.up / "mill-build"
@@ -46,11 +46,18 @@ class MillBuildRootModule()(implicit
 
   override def scalaVersion = "2.13.10"
 
-  def parseBuildFiles: T[FileImportGraph] = T.input {
-    FileImportGraph.parseBuildFiles(
-      millBuildRootModule.topLevelProjectRoot,
-      millBuildRootModule.projectRoot / os.up
-    )
+  def allBuildFiles = T.sources {
+    MillBuildRootModule
+      .parseBuildFiles(millBuildRootModuleInfo)
+      .seenScripts
+      .keys
+      .map(PathRef(_))
+      .toSeq
+  }
+
+  def parseBuildFiles = T {
+    allBuildFiles()
+    MillBuildRootModule.parseBuildFiles(millBuildRootModuleInfo)
   }
 
   override def repositoriesTask: Task[Seq[Repository]] = {
@@ -132,7 +139,7 @@ class MillBuildRootModule()(implicit
   def enclosingClasspath = T.sources {
     millBuildRootModule.enclosingClasspath.map(p => mill.api.PathRef(p, quick = true))
   }
-  override def unmanagedClasspath: T[Agg[PathRef]] = T{
+  override def unmanagedClasspath: T[Agg[PathRef]] = T {
     enclosingClasspath() ++ lineNumberPluginClasspath()
   }
 
@@ -185,6 +192,13 @@ object MillBuildRootModule {
       topLevelProjectRoot: os.Path
   )
 
+  def parseBuildFiles(millBuildRootModule: MillBuildRootModule.Info) = {
+    FileImportGraph.parseBuildFiles(
+      millBuildRootModule.topLevelProjectRoot,
+      millBuildRootModule.projectRoot / os.up
+    )
+  }
+
   def generateWrappedSources(
       base: os.Path,
       scriptSources: Seq[PathRef],

From 2ff49e4bc14dcf207265107ab96268c4fec84978 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 14:33:08 +0800
Subject: [PATCH 16/27] .

---
 runner/src/mill/runner/MillBuildRootModule.scala | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 7936ebd7eb3..87a948953c8 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -30,7 +30,7 @@ class MillBuildRootModule()(implicit
     millBuildRootModuleInfo: MillBuildRootModule.Info
 ) extends RootModule() with ScalaModule {
 
-  override def millSourcePath = millBuildRootModule.projectRoot / os.up / "mill-build"
+  override def millSourcePath = millBuildRootModuleInfo.projectRoot / os.up / "mill-build"
 
   override def resolveDeps(
       deps: Task[Agg[BoundDep]],
@@ -113,12 +113,12 @@ class MillBuildRootModule()(implicit
     if (parsed.errors.nonEmpty) Result.Failure(parsed.errors.mkString("\n"))
     else {
       MillBuildRootModule.generateWrappedSources(
-        millBuildRootModule.projectRoot / os.up,
+        millBuildRootModuleInfo.projectRoot / os.up,
         scriptSources(),
         parsed.seenScripts,
         T.dest,
-        millBuildRootModule.enclosingClasspath,
-        millBuildRootModule.topLevelProjectRoot
+        millBuildRootModuleInfo.enclosingClasspath,
+        millBuildRootModuleInfo.topLevelProjectRoot
       )
       Result.Success(Seq(PathRef(T.dest)))
     }
@@ -137,7 +137,7 @@ class MillBuildRootModule()(implicit
   }
 
   def enclosingClasspath = T.sources {
-    millBuildRootModule.enclosingClasspath.map(p => mill.api.PathRef(p, quick = true))
+    millBuildRootModuleInfo.enclosingClasspath.map(p => mill.api.PathRef(p, quick = true))
   }
   override def unmanagedClasspath: T[Agg[PathRef]] = T {
     enclosingClasspath() ++ lineNumberPluginClasspath()
@@ -192,10 +192,10 @@ object MillBuildRootModule {
       topLevelProjectRoot: os.Path
   )
 
-  def parseBuildFiles(millBuildRootModule: MillBuildRootModule.Info) = {
+  def parseBuildFiles(millBuildRootModuleInfo: MillBuildRootModule.Info) = {
     FileImportGraph.parseBuildFiles(
-      millBuildRootModule.topLevelProjectRoot,
-      millBuildRootModule.projectRoot / os.up
+      millBuildRootModuleInfo.topLevelProjectRoot,
+      millBuildRootModuleInfo.projectRoot / os.up
     )
   }
 

From d227ee654f3b1eab4ad1b66711c306b5e9ca2f9d Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 14:52:38 +0800
Subject: [PATCH 17/27] update-patch

---
 ci/mill-bootstrap.patch | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/ci/mill-bootstrap.patch b/ci/mill-bootstrap.patch
index 13c9465df92..42b80893553 100644
--- a/ci/mill-bootstrap.patch
+++ b/ci/mill-bootstrap.patch
@@ -1,5 +1,5 @@
 diff --git a/build.sc b/build.sc
-index 0f664c99c3..7d8788e7a8 100644
+index 0f664c99c3..d738fbe351 100644
 --- a/build.sc
 +++ b/build.sc
 @@ -19,17 +19,18 @@ import com.github.lolgab.mill.mima.{
@@ -518,7 +518,7 @@ index 0f664c99c3..7d8788e7a8 100644
      os.copy(examplePath, T.dest / exampleStr, createFolders = true)
      os.copy(bootstrapLauncher().path, T.dest / exampleStr / "mill")
      val zip = T.dest / s"$exampleStr.zip"
-@@ -2018,47 +1735,6 @@ def exampleZips: Target[Seq[PathRef]] = T {
+@@ -2018,51 +1735,10 @@ def exampleZips: Target[Seq[PathRef]] = T {
  }
  
  def uploadToGithub(authKey: String) = T.command {
@@ -566,3 +566,18 @@ index 0f664c99c3..7d8788e7a8 100644
  }
  
  def validate(ev: Evaluator): Command[Unit] = T.command {
+-  T.task(MainModule.evaluateTasks(
++  mill.main.RunScript.evaluateTasksNamed(
+     ev.withFailFast(false),
+     Seq(
+       "__.compile",
+@@ -2075,7 +1751,8 @@ def validate(ev: Evaluator): Command[Unit] = T.command {
+       "docs.localPages"
+     ),
+     selectMode = SelectMode.Separated
+-  )(identity))()
++  )
++
+   ()
+ }
+ 

From e7ded2d20fde8563f68a5d0935bb03f3274fca90 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 14:55:37 +0800
Subject: [PATCH 18/27] .

---
 main/testkit/src/mill/testkit/MillTestkit.scala | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/main/testkit/src/mill/testkit/MillTestkit.scala b/main/testkit/src/mill/testkit/MillTestkit.scala
index cfd7d3cc2fd..f9a09c6dfe8 100644
--- a/main/testkit/src/mill/testkit/MillTestkit.scala
+++ b/main/testkit/src/mill/testkit/MillTestkit.scala
@@ -1,8 +1,8 @@
 package mill.testkit
 
 import mill._
-import mill.define.{Discover, TargetImpl, InputImpl}
-import mill.api.{DummyInputStream, Result, SystemStreams}
+import mill.define.{Discover, InputImpl, TargetImpl}
+import mill.api.{DummyInputStream, Result, SystemStreams, Val}
 import mill.api.Result.OuterStack
 import mill.api.Strict.Agg
 
@@ -109,7 +109,7 @@ trait MillTestKit {
       if (evaluated.failing.keyCount == 0) {
         Right(
           Tuple2(
-            evaluated.rawValues.head.asInstanceOf[Result.Success[T]].value,
+            evaluated.rawValues.head.asInstanceOf[Result.Success[Val]].value.value.asInstanceOf[T],
             evaluated.evaluated.collect {
               case t: TargetImpl[_]
                   if module.millInternal.targets.contains(t)

From d38944ed0960df6542f69f2baed87f0f49583cc6 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 15:11:49 +0800
Subject: [PATCH 19/27] cleanup

---
 .../feature/editing/test/src/MultiLevelBuildTests.scala   | 2 +-
 main/eval/src/mill/eval/Evaluator.scala                   | 2 +-
 runner/src/mill/runner/MillBuildRootModule.scala          | 8 ++------
 3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/integration/feature/editing/test/src/MultiLevelBuildTests.scala b/integration/feature/editing/test/src/MultiLevelBuildTests.scala
index b962f70cd1c..48b55d99264 100644
--- a/integration/feature/editing/test/src/MultiLevelBuildTests.scala
+++ b/integration/feature/editing/test/src/MultiLevelBuildTests.scala
@@ -58,7 +58,7 @@ object MultiLevelBuildTests extends IntegrationTestSuite {
      */
     def checkWatchedFiles(expected0: Seq[os.Path]*) = {
       for ((expectedWatched0, (frame, path)) <- expected0.zip(loadFrames(expected0.length))) {
-        val frameWatched = frame.evalWatched.map(_.path).sorted
+        val frameWatched = frame.evalWatched.map(_.path).sorted.filter(_.startsWith(wsRoot))
         val expectedWatched = expectedWatched0.sorted
         assert(frameWatched == expectedWatched)
       }
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 865c64e8b9c..9520d4aa1bc 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -545,7 +545,7 @@ class Evaluator private (
 
       val tickerPrefix = maybeTargetLabel.map { targetLabel =>
         val prefix = s"[$counterMsg] $targetLabel "
-        if (logRun) logger.ticker(prefix)
+        if (logRun && enableTicker) logger.ticker(prefix)
         prefix + "| "
       }
 
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 87a948953c8..af94a7d52f3 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -46,7 +46,7 @@ class MillBuildRootModule()(implicit
 
   override def scalaVersion = "2.13.10"
 
-  def allBuildFiles = T.sources {
+  def scriptSources = T.sources {
     MillBuildRootModule
       .parseBuildFiles(millBuildRootModuleInfo)
       .seenScripts
@@ -56,7 +56,7 @@ class MillBuildRootModule()(implicit
   }
 
   def parseBuildFiles = T {
-    allBuildFiles()
+    scriptSources()
     MillBuildRootModule.parseBuildFiles(millBuildRootModuleInfo)
   }
 
@@ -100,10 +100,6 @@ class MillBuildRootModule()(implicit
       Seq(ivy"com.lihaoyi::mill-moduledefs:${Versions.millModuledefsVersion}")
   }
 
-  def scriptSources: T[Seq[PathRef]] = T.sources {
-    for ((p, s) <- parseBuildFiles().seenScripts.toSeq) yield PathRef(p)
-  }
-
   override def generatedSources: T[Seq[PathRef]] = T {
     generateScriptSources()
   }

From f406c1089c0d15ca16573c33521f19170f92ec14 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 16:41:13 +0800
Subject: [PATCH 20/27] wip

---
 example/tasks/2-primary-tasks/build.sc        |  4 +--
 main/eval/src/mill/eval/Evaluator.scala       | 30 +++++++++----------
 .../src/mill/testkit/MillTestkit.scala        | 12 ++++++--
 .../mill/scalajslib/HelloJSWorldTests.scala   |  4 +--
 .../HelloNativeWorldTests.scala               |  4 +--
 5 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/example/tasks/2-primary-tasks/build.sc b/example/tasks/2-primary-tasks/build.sc
index 670ad446e97..ea06479d28a 100644
--- a/example/tasks/2-primary-tasks/build.sc
+++ b/example/tasks/2-primary-tasks/build.sc
@@ -34,10 +34,10 @@ def lineCount: T[Int] = T {
 
 > ./mill show lineCount
 Computing line count
-18
+16
 
 > ./mill show lineCount # line count already cached, doesn't need to be computed
-18
+16
 
 */
 
diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 9520d4aa1bc..00262c454f4 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -179,15 +179,15 @@ class Evaluator private (
   def getFailing(
       sortedGroups: MultiBiMap[Either[Task[_], Labelled[Any]], Task[_]],
       results: collection.Map[Task[_], TaskResult[(Val, Int)]]
-  ): MultiBiMap.Mutable[Either[Task[_], Labelled[_]], Failing[_]] = {
-    val failing = new MultiBiMap.Mutable[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]]
+  ): MultiBiMap.Mutable[Either[Task[_], Labelled[_]], Failing[Val]] = {
+    val failing = new MultiBiMap.Mutable[Either[Task[_], Labelled[_]], Result.Failing[Val]]
     for ((k, vs) <- sortedGroups.items()) {
       failing.addAll(
         k,
         Loose.Agg.from(
           vs.items.flatMap(results.get).collect {
-            case er @ TaskResult(f: mill.api.Result.Failing[_], _) =>
-              f
+            case er @ TaskResult(f: Result.Failing[(Val, Int)], _) =>
+              f.map(_._1)
           }
         )
       )
@@ -455,10 +455,10 @@ class Evaluator private (
               }
 
             newResults(labelledNamedTask.task) match {
-              case TaskResult(mill.api.Result.Failure(_, Some((v, _))), _) =>
+              case TaskResult(Result.Failure(_, Some((v, _))), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
-              case TaskResult(mill.api.Result.Success((v, _)), _) =>
+              case TaskResult(Result.Success((v, _)), _) =>
                 handleTaskResult(v, v.##, paths.meta, inputsHash, labelledNamedTask)
 
               case _ =>
@@ -540,7 +540,7 @@ class Evaluator private (
           target <- nonEvaluatedTargets
           item <- target.inputs.filterNot(group.contains)
         } yield results(item).map(_._1)
-        inputResults.forall(_.result.isInstanceOf[mill.api.Result.Success[_]])
+        inputResults.forall(_.result.isInstanceOf[Result.Success[_]])
       }
 
       val tickerPrefix = maybeTargetLabel.map { targetLabel =>
@@ -568,7 +568,7 @@ class Evaluator private (
           .collect { case Result.Success((v, _)) => v }
 
         val res = {
-          if (targetInputValues.length != task.inputs.length) mill.api.Result.Skipped
+          if (targetInputValues.length != task.inputs.length) Result.Skipped
           else {
             val args = new Ctx(
               args = targetInputValues.map(_.value).toIndexedSeq,
@@ -596,7 +596,7 @@ class Evaluator private (
               try task.evaluate(args).map(Val(_))
               catch {
                 case NonFatal(e) =>
-                  mill.api.Result.Exception(
+                  Result.Exception(
                     e,
                     new OuterStack(new Exception().getStackTrace.toIndexedSeq)
                   )
@@ -786,7 +786,7 @@ object Evaluator {
     )
   }
 
-  case class TaskResult[T](result: Result[T], recalcOpt: Option[() => mill.api.Result[T]]) {
+  case class TaskResult[T](result: Result[T], recalcOpt: Option[() => Result[T]]) {
     def map[V](f: T => V) = TaskResult[V](
       result.map(f),
       recalcOpt.map(r => () => r().map(f))
@@ -794,18 +794,18 @@ object Evaluator {
   }
 
   case class Results(
-      rawValues: Seq[mill.api.Result[Val]],
+      rawValues: Seq[Result[Val]],
       evaluated: Agg[Task[_]],
       transitive: Agg[Task[_]],
-      failing: MultiBiMap[Either[Task[_], Labelled[_]], mill.api.Result.Failing[_]],
+      failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[Val]],
       results: collection.Map[Task[_], TaskResult[Val]]
   ) {
-    def values: Seq[Any] = rawValues.collect { case mill.api.Result.Success(v) => v }
+    def values: Seq[Any] = rawValues.collect { case Result.Success(v) => v }
     private def copy(
         rawValues: Seq[Result[Val]] = rawValues,
         evaluated: Agg[Task[_]] = evaluated,
         transitive: Agg[Task[_]] = transitive,
-        failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[_]] = failing,
+        failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[Val]] = failing,
         results: collection.Map[Task[_], TaskResult[Val]]
     ): Results = new Results(
       rawValues,
@@ -821,7 +821,7 @@ object Evaluator {
         Seq[Result[Any]],
         Agg[Task[_]],
         Agg[Task[_]],
-        MultiBiMap[Either[Task[_], Labelled[_]], Failing[_]],
+        MultiBiMap[Either[Task[_], Labelled[_]], Failing[Val]],
         collection.Map[Task[_], TaskResult[_]]
     )] = Some((
       results.rawValues,
diff --git a/main/testkit/src/mill/testkit/MillTestkit.scala b/main/testkit/src/mill/testkit/MillTestkit.scala
index f9a09c6dfe8..2581050ba32 100644
--- a/main/testkit/src/mill/testkit/MillTestkit.scala
+++ b/main/testkit/src/mill/testkit/MillTestkit.scala
@@ -120,8 +120,16 @@ trait MillTestKit {
         )
       } else {
         Left(
-          evaluated.failing.lookupKey(evaluated.failing.keys().next).items.next()
-            .asInstanceOf[Result.Failing[T]]
+          evaluated
+            .failing
+            .lookupKey(evaluated.failing.keys().next)
+            .items
+            .next()
+            .asInstanceOf[Result.Failing[Val]]
+            .map{(x: Val) =>
+              x.value.asInstanceOf[T]
+            }
+
         )
       }
     }
diff --git a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
index 50ae3bc5265..af794e3de18 100644
--- a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
@@ -28,8 +28,8 @@ object HelloJSWorldTests extends TestSuite {
   }
 
   object HelloJSWorld extends TestUtil.BaseModule {
-    val scalaVersions = Seq("2.13.3", "3.0.0-RC1", "2.12.12", "2.11.12")
-    val scalaJSVersions = Seq("1.8.0", "1.3.1", "1.0.1")
+    val scalaVersions = Seq("2.13.3", "2.12.12", "2.11.12")
+    val scalaJSVersions = Seq("1.8.0")
     val matrix = for {
       scala <- scalaVersions
       scalaJS <- scalaJSVersions
diff --git a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
index 1019ddcec35..4ce32ef1ab4 100644
--- a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
+++ b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
@@ -38,8 +38,8 @@ object HelloNativeWorldTests extends TestSuite {
         extends Cross.ToSegments[ReleaseMode](v => List(v.toString))
 
     val matrix = for {
-      scala <- Seq("3.2.1", "3.1.3", scala213, "2.12.13", "2.11.12")
-      scalaNative <- Seq(scalaNative04, "0.4.9")
+      scala <- Seq("3.2.1", scala213, "2.12.13", "2.11.12")
+      scalaNative <- Seq(scalaNative04)
       mode <- List(ReleaseMode.Debug, ReleaseMode.ReleaseFast)
       if !(ZincWorkerUtil.isScala3(scala) && scalaNative == scalaNative04)
     } yield (scala, scalaNative, mode)

From a07fc7d044640bd59d76bea8809842b30153afe9 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 16:42:27 +0800
Subject: [PATCH 21/27] wip

---
 example/tasks/2-primary-tasks/build.sc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/example/tasks/2-primary-tasks/build.sc b/example/tasks/2-primary-tasks/build.sc
index ea06479d28a..d8483daebe2 100644
--- a/example/tasks/2-primary-tasks/build.sc
+++ b/example/tasks/2-primary-tasks/build.sc
@@ -111,7 +111,7 @@ def hugeFileName = T{
 /** Usage
 
 > ./mill show lineCount
-18
+16
 
 > ./mill show hugeFileName # This still runs `largestFile` even though `lineCount() < 999`
 Finding Largest File

From 5eae38170bfc403137f8d41a0ec97a8861fb0b9b Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 20:14:27 +0800
Subject: [PATCH 22/27] .

---
 main/eval/src/mill/eval/Evaluator.scala                     | 6 +++---
 scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala | 4 ++--
 .../src/mill/scalanativelib/HelloNativeWorldTests.scala     | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 00262c454f4..7dfacffc04d 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -800,7 +800,7 @@ object Evaluator {
       failing: MultiBiMap[Either[Task[_], Labelled[_]], Result.Failing[Val]],
       results: collection.Map[Task[_], TaskResult[Val]]
   ) {
-    def values: Seq[Any] = rawValues.collect { case Result.Success(v) => v }
+    def values: Seq[Val] = rawValues.collect { case Result.Success(v) => v }
     private def copy(
         rawValues: Seq[Result[Val]] = rawValues,
         evaluated: Agg[Task[_]] = evaluated,
@@ -914,14 +914,14 @@ object Evaluator {
           throw exceptionFactory(r)
         case r =>
           // Input is a single-item Agg, so we also expect a single-item result
-          val Seq(e: T) = r.values
+          val Seq(Val(e: T)) = r.values
           e
       }
     def apply[T: ClassTag](tasks: Seq[Task[T]]): Seq[T] =
       evaluator.evaluate(tasks) match {
         case r if r.failing.items().nonEmpty =>
           throw exceptionFactory(r)
-        case r => r.values.asInstanceOf[Seq[T]]
+        case r => r.values.map(_.value).asInstanceOf[Seq[T]]
       }
   }
 
diff --git a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
index af794e3de18..50ae3bc5265 100644
--- a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
@@ -28,8 +28,8 @@ object HelloJSWorldTests extends TestSuite {
   }
 
   object HelloJSWorld extends TestUtil.BaseModule {
-    val scalaVersions = Seq("2.13.3", "2.12.12", "2.11.12")
-    val scalaJSVersions = Seq("1.8.0")
+    val scalaVersions = Seq("2.13.3", "3.0.0-RC1", "2.12.12", "2.11.12")
+    val scalaJSVersions = Seq("1.8.0", "1.3.1", "1.0.1")
     val matrix = for {
       scala <- scalaVersions
       scalaJS <- scalaJSVersions
diff --git a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
index 4ce32ef1ab4..1019ddcec35 100644
--- a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
+++ b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
@@ -38,8 +38,8 @@ object HelloNativeWorldTests extends TestSuite {
         extends Cross.ToSegments[ReleaseMode](v => List(v.toString))
 
     val matrix = for {
-      scala <- Seq("3.2.1", scala213, "2.12.13", "2.11.12")
-      scalaNative <- Seq(scalaNative04)
+      scala <- Seq("3.2.1", "3.1.3", scala213, "2.12.13", "2.11.12")
+      scalaNative <- Seq(scalaNative04, "0.4.9")
       mode <- List(ReleaseMode.Debug, ReleaseMode.ReleaseFast)
       if !(ZincWorkerUtil.isScala3(scala) && scalaNative == scalaNative04)
     } yield (scala, scalaNative, mode)

From 080527d91a4b437eab2fe7637052e051d5713863 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 21:14:00 +0800
Subject: [PATCH 23/27] fix main.__.test

---
 main/eval/src/mill/eval/Evaluator.scala            | 2 +-
 main/eval/test/src/mill/eval/EvaluationTests.scala | 4 ++--
 main/testkit/src/mill/testkit/MillTestkit.scala    | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 7dfacffc04d..6eb69d3488c 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -405,7 +405,7 @@ class Evaluator private (
           case (`inputsHash`, upToDate) =>
             // worker cached and up-to-date
             Some(upToDate)
-          case (_, obsolete: AutoCloseable) =>
+          case (_, Val(obsolete: AutoCloseable)) =>
             // worker cached but obsolete, needs to be closed
             try {
               logger.debug(s"Closing previous worker: ${labelledNamedTask.segments.render}")
diff --git a/main/eval/test/src/mill/eval/EvaluationTests.scala b/main/eval/test/src/mill/eval/EvaluationTests.scala
index 47d0d3241f8..fd2ee31f4be 100644
--- a/main/eval/test/src/mill/eval/EvaluationTests.scala
+++ b/main/eval/test/src/mill/eval/EvaluationTests.scala
@@ -43,7 +43,7 @@ class EvaluationTests(threadCount: Option[Int]) extends TestSuite {
         evaled.evaluated.indexed.partition(expEvaled.contains)
 
       assert(
-        evaled.values == Seq(expValue),
+        evaled.values.map(_.value) == Seq(expValue),
         matchingReturnedEvaled.toSet == expEvaled.toSet,
         extraEvaled == -1 || extra.length == extraEvaled
       )
@@ -53,7 +53,7 @@ class EvaluationTests(threadCount: Option[Int]) extends TestSuite {
         val evaled2 = evaluator.evaluate(Agg(target))
         val expecteSecondRunEvaluated = Agg()
         assert(
-          evaled2.values == evaled.values,
+          evaled2.values.map(_.value) == evaled.values.map(_.value),
           evaled2.evaluated == expecteSecondRunEvaluated
         )
       }
diff --git a/main/testkit/src/mill/testkit/MillTestkit.scala b/main/testkit/src/mill/testkit/MillTestkit.scala
index 2581050ba32..016cda0eaca 100644
--- a/main/testkit/src/mill/testkit/MillTestkit.scala
+++ b/main/testkit/src/mill/testkit/MillTestkit.scala
@@ -140,7 +140,7 @@ trait MillTestKit {
 
       val cleaned = res.rawValues.map {
         case Result.Exception(ex, _) => Result.Exception(ex, new OuterStack(Nil))
-        case x => x
+        case x => x.map(_.value)
       }
 
       assert(

From 137e47986cfb4e6433cf3a106bd47bd72bd63e04 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 21:22:06 +0800
Subject: [PATCH 24/27] .

---
 main/api/src/mill/api/Result.scala           | 4 ++++
 scalalib/src/mill/scalalib/GenIdeaImpl.scala | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/main/api/src/mill/api/Result.scala b/main/api/src/mill/api/Result.scala
index ab55c0aaad3..efc85651890 100644
--- a/main/api/src/mill/api/Result.scala
+++ b/main/api/src/mill/api/Result.scala
@@ -11,6 +11,8 @@ sealed trait Result[+T] {
   def map[V](f: T => V): Result[V]
   def flatMap[V](f: T => Result[V]): Result[V]
   def asSuccess: Option[Result.Success[T]] = None
+  def asFailing: Option[Result.Failing[T]] = None
+
 }
 
 object Result {
@@ -56,6 +58,8 @@ object Result {
   sealed trait Failing[+T] extends Result[T] {
     def map[V](f: T => V): Failing[V]
     def flatMap[V](f: T => Result[V]): Failing[V]
+    override def asFailing: Option[Result.Failing[T]] = Some(this)
+
   }
 
   /**
diff --git a/scalalib/src/mill/scalalib/GenIdeaImpl.scala b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
index 4f0c97cc613..10433d13257 100755
--- a/scalalib/src/mill/scalalib/GenIdeaImpl.scala
+++ b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
@@ -243,7 +243,7 @@ case class GenIdeaImpl(
       evaluator.evaluate(resolveTasks) match {
         case r if r.failing.items().nonEmpty =>
           throw GenIdeaException(s"Failure during resolving modules: ${Evaluator.formatFailing(r)}")
-        case r => r.values.asInstanceOf[Seq[ResolvedModule]]
+        case r => r.values.map(_.value).asInstanceOf[Seq[ResolvedModule]]
       }
 
     val moduleLabels = modules.map(_.swap).toMap
@@ -537,6 +537,7 @@ case class GenIdeaImpl(
             )
           )
           .values
+          .map(_.value)
 
         val generatedSourcePaths = generatedSourcePathRefs.map(_.path)
         val normalSourcePaths = (allSourcesPathRefs
@@ -550,6 +551,7 @@ case class GenIdeaImpl(
                 .evaluate(Agg(x.scalaVersion))
                 .values
                 .head
+                .value
                 .asInstanceOf[String]
             )
           case _ => None

From 28d6ac4e050529e083c6fe58682918e5e4829d23 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Wed, 3 May 2023 21:28:43 +0800
Subject: [PATCH 25/27] .

---
 .../feature/editing/test/src/MultiLevelBuildTests.scala    | 7 ++++++-
 main/testkit/src/mill/testkit/MillTestkit.scala            | 3 ++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/integration/feature/editing/test/src/MultiLevelBuildTests.scala b/integration/feature/editing/test/src/MultiLevelBuildTests.scala
index 48b55d99264..c0a703033c5 100644
--- a/integration/feature/editing/test/src/MultiLevelBuildTests.scala
+++ b/integration/feature/editing/test/src/MultiLevelBuildTests.scala
@@ -58,7 +58,12 @@ object MultiLevelBuildTests extends IntegrationTestSuite {
      */
     def checkWatchedFiles(expected0: Seq[os.Path]*) = {
       for ((expectedWatched0, (frame, path)) <- expected0.zip(loadFrames(expected0.length))) {
-        val frameWatched = frame.evalWatched.map(_.path).sorted.filter(_.startsWith(wsRoot))
+        val frameWatched = frame
+          .evalWatched
+          .map(_.path)
+          .sorted.filter(_.startsWith(wsRoot))
+          .filter(!_.segments.contains("mill-launcher"))
+
         val expectedWatched = expectedWatched0.sorted
         assert(frameWatched == expectedWatched)
       }
diff --git a/main/testkit/src/mill/testkit/MillTestkit.scala b/main/testkit/src/mill/testkit/MillTestkit.scala
index 016cda0eaca..63ab77f77df 100644
--- a/main/testkit/src/mill/testkit/MillTestkit.scala
+++ b/main/testkit/src/mill/testkit/MillTestkit.scala
@@ -125,7 +125,8 @@ trait MillTestKit {
             .lookupKey(evaluated.failing.keys().next)
             .items
             .next()
-            .asInstanceOf[Result.Failing[Val]]
+            .asFailing
+            .get
             .map{(x: Val) =>
               x.value.asInstanceOf[T]
             }

From 8a623c4fa6fd6f2c9cbeebdf6ddd098bb11867ca Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Thu, 4 May 2023 09:34:55 +0800
Subject: [PATCH 26/27] cleanups

---
 main/eval/src/mill/eval/Evaluator.scala | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/main/eval/src/mill/eval/Evaluator.scala b/main/eval/src/mill/eval/Evaluator.scala
index 6eb69d3488c..f7d6c6d88b8 100644
--- a/main/eval/src/mill/eval/Evaluator.scala
+++ b/main/eval/src/mill/eval/Evaluator.scala
@@ -123,14 +123,14 @@ class Evaluator private (
 
     val (sortedGroups, transitive) = Evaluator.plan(goals)
     val evaluated = new Agg.Mutable[Task[_]]
-    val results = mutable.LinkedHashMap.empty[Task[_], TaskResult[(Val, Int)]]
+    var results = Map.empty[Task[_], TaskResult[(Val, Int)]]
     var someTaskFailed: Boolean = false
 
     val timings = mutable.ArrayBuffer.empty[(Either[Task[_], Labelled[_]], Int, Boolean)]
     for (((terminal, group), i) <- sortedGroups.items().zipWithIndex) {
       if (failFast && someTaskFailed) {
         // we exit early and set aborted state for all left tasks
-        group.iterator.foreach { task => results.put(task, TaskResult(Aborted, None)) }
+        group.iterator.foreach { task => results += (task -> TaskResult(Aborted, None)) }
 
       } else {
 
@@ -143,7 +143,7 @@ class Evaluator private (
         val startTime = System.currentTimeMillis()
 
         // Increment the counter message by 1 to go from 1/10 to 10/10 instead of 0/10 to 9/10
-        val counterMsg = s"${(i + 1)}/${sortedGroups.keyCount}"
+        val counterMsg = s"${i + 1}/${sortedGroups.keyCount}"
 
         val Evaluated(newResults, newEvaluated, cached) = evaluateGroupCached(
           terminal = terminal,
@@ -157,8 +157,8 @@ class Evaluator private (
         someTaskFailed =
           someTaskFailed || newResults.exists(task => !task._2.result.isInstanceOf[Success[_]])
 
-        for (ev <- newEvaluated) evaluated.append(ev)
-        for ((k, v) <- newResults) results.put(k, v)
+        evaluated.appendAll(newEvaluated)
+        results ++= newResults
         val endTime = System.currentTimeMillis()
 
         timings.append((terminal, (endTime - startTime).toInt, cached))
@@ -310,7 +310,7 @@ class Evaluator private (
   protected def evaluateGroupCached(
       terminal: Terminal,
       group: Agg[Task[_]],
-      results: collection.Map[Task[_], TaskResult[(Val, Int)]],
+      results: Map[Task[_], TaskResult[(Val, Int)]],
       counterMsg: String,
       zincProblemReporter: Int => Option[CompileProblemReporter],
       testReporter: TestReporter,
@@ -357,7 +357,7 @@ class Evaluator private (
       case Left(task) =>
         val (newResults, newEvaluated) = evaluateGroup(
           group,
-          results.toMap,
+          results,
           inputsHash,
           paths = None,
           maybeTargetLabel = None,

From 3a35c1fff223fefe3420b41007f83f19c98e5d49 Mon Sep 17 00:00:00 2001
From: Your Name <haoyi.sg@gmail.com>
Date: Thu, 4 May 2023 09:41:08 +0800
Subject: [PATCH 27/27] .

---
 main/testkit/src/mill/testkit/MillTestkit.scala | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/main/testkit/src/mill/testkit/MillTestkit.scala b/main/testkit/src/mill/testkit/MillTestkit.scala
index 63ab77f77df..a923a63410d 100644
--- a/main/testkit/src/mill/testkit/MillTestkit.scala
+++ b/main/testkit/src/mill/testkit/MillTestkit.scala
@@ -127,10 +127,9 @@ trait MillTestKit {
             .next()
             .asFailing
             .get
-            .map{(x: Val) =>
+            .map { (x: Val) =>
               x.value.asInstanceOf[T]
             }
-
         )
       }
     }