improve the external clippy usage

Signed-off-by: onur-ozkan <work@onurozkan.dev>

config.example.toml

@@ -233,15 +233,10 @@
 # Instead of downloading the src/stage0 version of cargo-clippy specified,
 # use this cargo-clippy binary instead as the stage0 snapshot cargo-clippy.
 #
-# Note that this option must be used together with `clippy-driver` below.
+# Note that this option should be used together with `rustc` option above,
+# otherwise clippy will most likely fail due to toolchain conflict.
 #cargo-clippy = "/path/to/cargo-clippy"
 
-# Instead of downloading the src/stage0 version of clippy-driver specified,
-# use this clippy-driver binary instead as the stage0 snapshot clippy-driver.
-#
-# Note that this option must be used together with `cargo-clippy` above.
-#clippy-driver = "/path/to/clippy-driver"
-
 # Whether to build documentation by default. If false, rustdoc and
 # friends will still be compiled but they will not be used to generate any
 # documentation.

src/bootstrap/src/core/build_steps/tool.rs

@@ -1148,32 +1148,3 @@ impl<'a> Builder<'a> {
         cmd
     }
 }
-
-pub(crate) fn install_external_stage0_clippy(builder: &Builder<'_>) -> PathBuf {
-    if builder.config.dry_run() {
-        return PathBuf::default();
-    }
-
-    builder.info("Installing external clippy to stage0 sysroot.");
-
-    let (Some(external_cargo_clippy), Some(external_clippy_driver)) =
-        (&builder.config.external_cargo_clippy, &builder.config.external_clippy_driver)
-    else {
-        panic!("`build.cargo-clippy` and `build.clippy-driver` must be configured together.");
-    };
-
-    let host = builder.config.build;
-    let bindir = builder.out.join(host.triple).join("stage0/bin");
-    t!(fs::create_dir_all(&bindir));
-
-    let cargo_clippy_destination = bindir.join(exe("cargo-clippy", host));
-    let _ = fs::remove_file(&cargo_clippy_destination);
-    builder.copy_link(external_cargo_clippy, &cargo_clippy_destination);
-
-    let clippy_driver_destination = bindir.join(exe("clippy-driver", host));
-    let _ = fs::remove_file(&clippy_driver_destination);
-    builder.copy_link(external_clippy_driver, &clippy_driver_destination);
-
-    assert!(cargo_clippy_destination.exists());
-    cargo_clippy_destination
-}

src/bootstrap/src/core/builder.rs

@@ -1298,12 +1298,11 @@ impl<'a> Builder<'a> {
 
     pub fn cargo_clippy_cmd(&self, run_compiler: Compiler) -> BootstrapCommand {
         if run_compiler.stage == 0 {
-            let cargo_clippy = if self.config.external_cargo_clippy.is_some() {
-                tool::install_external_stage0_clippy(self)
-            } else {
-                // `ensure(Clippy { stage: 0 })` *builds* clippy with stage0, it doesn't use the beta clippy.
-                self.build.config.download_clippy()
-            };
+            let cargo_clippy = self
+                .config
+                .initial_cargo_clippy
+                .clone()
+                .unwrap_or_else(|| self.build.config.download_clippy());
 
             let mut cmd = command(cargo_clippy);
             cmd.env("CARGO", &self.initial_cargo);

src/bootstrap/src/core/config/config.rs

@@ -336,8 +336,8 @@ pub struct Config {
     // These are either the stage0 downloaded binaries or the locally installed ones.
     pub initial_cargo: PathBuf,
     pub initial_rustc: PathBuf,
+    pub initial_cargo_clippy: Option<PathBuf>,
 
-    pub external_cargo_clippy: Option<PathBuf>,
     pub external_clippy_driver: Option<PathBuf>,
 
     #[cfg(not(test))]
@@ -830,7 +830,6 @@ define_config! {
         rustc: Option<PathBuf> = "rustc",
         rustfmt: Option<PathBuf> = "rustfmt",
         cargo_clippy: Option<PathBuf> = "cargo-clippy",
-        clippy_driver: Option<PathBuf> = "clippy-driver",
         docs: Option<bool> = "docs",
         compiler_docs: Option<bool> = "compiler-docs",
         library_docs_private_items: Option<bool> = "library-docs-private-items",
@@ -1426,7 +1425,6 @@ impl Config {
             rustc,
             rustfmt,
             cargo_clippy,
-            clippy_driver,
             docs,
             compiler_docs,
             library_docs_private_items,
@@ -1479,6 +1477,12 @@ impl Config {
             config.out = absolute(&config.out).expect("can't make empty path absolute");
         }
 
+        if cargo_clippy.is_some() && rustc.is_none() {
+            println!(
+                "WARNING: Using `build.cargo-clippy` without `build.rustc` usually fails due to toolchain conflict."
+            );
+        }
+
         config.initial_rustc = if let Some(rustc) = rustc {
             if !flags.skip_stage0_validation {
                 config.check_stage0_version(&rustc, "rustc");
@@ -1509,13 +1513,7 @@ impl Config {
                 .join(exe("cargo", config.build))
         };
 
-        assert_eq!(
-            cargo_clippy.is_some(),
-            clippy_driver.is_some(),
-            "`build.cargo-clippy` and `build.clippy-driver` must be configured together."
-        );
-        config.external_cargo_clippy = cargo_clippy;
-        config.external_clippy_driver = clippy_driver;
+        config.initial_cargo_clippy = cargo_clippy;
 
         // NOTE: it's important this comes *after* we set `initial_rustc` just above.
         if config.dry_run() {