Skip unpublish on projects marked skip on publish

src/main/scala/BintrayPlugin.scala

@@ -103,10 +103,7 @@ object BintrayPlugin extends AutoPlugin {
       }
     },
     bintrayEnsureBintrayPackageExists := ensurePackageTask.value,
-    bintrayUnpublish := Def.task {
-      val repo = bintrayRepo.value
-      repo.unpublish(bintrayPackage.value, version.value, streams.value.log)
-    }.dependsOn(bintrayEnsureBintrayPackageExists, bintrayEnsureLicenses).value,
+    bintrayUnpublish := dynamicallyBintrayUnpublish.value,
     bintrayRemoteSign := {
       val repo = bintrayRepo.value
       repo.remoteSign(bintrayPackage.value, version.value, streams.value.log)
@@ -155,6 +152,26 @@ object BintrayPlugin extends AutoPlugin {
       (if (bintrayReleaseOnPublish.value) bintrayRelease else warnToRelease).dependsOn(publishTask(publishConfiguration, deliver))
     } dependsOn(bintrayEnsureBintrayPackageExists, bintrayEnsureLicenses)
 
+  // uses taskDyn because it can return one of two potential tasks
+  // as its result, each with their own dependencies
+  // see also: http://www.scala-sbt.org/0.13/docs/Tasks.html#Dynamic+Computations+with
+  private def dynamicallyBintrayUnpublish: Initialize[Task[Unit]] =
+    taskDyn {
+      val repo = bintrayRepo.value
+      val sk = ((skip in publish) ?? false).value
+      val s = streams.value
+      val ref = thisProjectRef.value
+      if (sk) Def.task {
+        s.log.debug(s"Skipping bintrayUnpublish for ${ref.project}")
+      } else dynamicallyBintrayUnpublish0
+    }
+
+  private def dynamicallyBintrayUnpublish0: Initialize[Task[Unit]] =
+    Def.task {
+      val repo = bintrayRepo.value
+      repo.unpublish(bintrayPackage.value, version.value, streams.value.log)
+    }.dependsOn(bintrayEnsureBintrayPackageExists, bintrayEnsureLicenses)
+
   private def warnToRelease: Initialize[Task[Unit]] =
     task {
       val log = streams.value.log

src/main/scala/BintrayRepo.scala

@@ -80,7 +80,8 @@ case class BintrayRepo(credential: BintrayCredentials, org: Option[String], repo
   /** unpublish (delete) a version of a package */
   def unpublish(packageName: String, vers: String, log: Logger): Unit =
     await.result(repo.get(packageName).version(vers).delete(asStatusAndBody)) match {
-      case (200, _) =>  log.info(s"$owner/$packageName@$vers was discarded")
+      case (200, _) => log.info(s"$owner/$packageName@$vers was discarded")
+      case (404, _) => log.warn(s"$owner/$packageName@$vers was not found")
       case (_, fail) => sys.error(s"failed to discard $owner/$packageName@$vers: $fail")
     }