Rollup merge of #135231 - Zalathar:test-step-notes, r=jieyouxu

bootstrap: Add more comments to some of the test steps

Some of the test steps have names that don't clearly indicate what they actually do.

While there is ongoing experimental work to actually rename the steps (e.g. #135071), that's dependent on figuring out what the new names should actually be. In the meantime, we can still improve things by adding comments to help describe the steps, which will remain useful even after any renaming.

src/bootstrap/src/core/build_steps/test.rs

@@ -31,6 +31,7 @@ use crate::{CLang, DocTests, GitRepo, Mode, PathSet, envify};
 
 const ADB_TEST_DIR: &str = "/data/local/tmp/work";
 
+/// Runs `cargo test` on various internal tools used by bootstrap.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct CrateBootstrap {
     path: PathBuf,
@@ -43,13 +44,21 @@ impl Step for CrateBootstrap {
     const DEFAULT: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        // This step is responsible for several different tool paths. By default
+        // it will test all of them, but requesting specific tools on the
+        // command-line (e.g. `./x test suggest-tests`) will test only the
+        // specified tools.
         run.path("src/tools/jsondoclint")
             .path("src/tools/suggest-tests")
             .path("src/tools/replace-version-placeholder")
+            // We want `./x test tidy` to _run_ the tidy tool, not its tests.
+            // So we need a separate alias to test the tidy tool itself.
             .alias("tidyselftest")
     }
 
     fn make_run(run: RunConfig<'_>) {
+        // Create and ensure a separate instance of this step for each path
+        // that was selected on the command-line (or selected by default).
         for path in run.paths {
             let path = path.assert_single_path().path.clone();
             run.builder.ensure(CrateBootstrap { host: run.target, path });
@@ -60,6 +69,8 @@ impl Step for CrateBootstrap {
         let bootstrap_host = builder.config.build;
         let compiler = builder.compiler(0, bootstrap_host);
         let mut path = self.path.to_str().unwrap();
+
+        // Map alias `tidyselftest` back to the actual crate path of tidy.
         if path == "tidyselftest" {
             path = "src/tools/tidy";
         }
@@ -212,6 +223,9 @@ impl Step for HtmlCheck {
     }
 }
 
+/// Builds cargo and then runs the `src/tools/cargotest` tool, which checks out
+/// some representative crate repositories and runs `cargo test` on them, in
+/// order to test cargo.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Cargotest {
     stage: u32,
@@ -257,6 +271,7 @@ impl Step for Cargotest {
     }
 }
 
+/// Runs `cargo test` for cargo itself.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Cargo {
     stage: u32,
@@ -385,6 +400,7 @@ impl Step for RustAnalyzer {
     }
 }
 
+/// Runs `cargo test` for rustfmt.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Rustfmt {
     stage: u32,
@@ -589,6 +605,8 @@ impl Step for Miri {
     }
 }
 
+/// Runs `cargo miri test` to demonstrate that `src/tools/miri/cargo-miri`
+/// works and that libtest works under miri.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct CargoMiri {
     target: TargetSelection,
@@ -1020,6 +1038,10 @@ impl Step for RustdocGUI {
     }
 }
 
+/// Runs `src/tools/tidy` and `cargo fmt --check` to detect various style
+/// problems in the repository.
+///
+/// (To run the tidy tool's internal tests, use the alias "tidyselftest" instead.)
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Tidy;
 
@@ -1230,6 +1252,8 @@ impl Step for RunMakeSupport {
     }
 }
 
+/// Runs `cargo test` on the `src/tools/run-make-support` crate.
+/// That crate is used by run-make tests.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct CrateRunMakeSupport {
     host: TargetSelection,
@@ -2466,6 +2490,10 @@ fn markdown_test(builder: &Builder<'_>, compiler: Compiler, markdown: &Path) ->
     }
 }
 
+/// Runs `cargo test` for the compiler crates in `compiler/`.
+///
+/// (This step does not test `rustc_codegen_cranelift` or `rustc_codegen_gcc`,
+/// which have their own separate test steps.)
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct CrateLibrustc {
     compiler: Compiler,
@@ -2494,6 +2522,7 @@ impl Step for CrateLibrustc {
     fn run(self, builder: &Builder<'_>) {
         builder.ensure(compile::Std::new(self.compiler, self.target));
 
+        // To actually run the tests, delegate to a copy of the `Crate` step.
         builder.ensure(Crate {
             compiler: self.compiler,
             target: self.target,
@@ -2619,6 +2648,13 @@ fn prepare_cargo_test(
     cargo
 }
 
+/// Runs `cargo test` for standard library crates.
+///
+/// (Also used internally to run `cargo test` for compiler crates.)
+///
+/// FIXME(Zalathar): Try to split this into two separate steps: a user-visible
+/// step for testing standard library crates, and an internal step used for both
+/// library crates and compiler crates.
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Crate {
     pub compiler: Compiler,
@@ -3552,6 +3588,10 @@ impl Step for CodegenGCC {
     }
 }
 
+/// Test step that does two things:
+/// - Runs `cargo test` for the `src/etc/test-float-parse` tool.
+/// - Invokes the `test-float-parse` tool to test the standard library's
+///   float parsing routines.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct TestFloatParse {
     path: PathBuf,
@@ -3625,6 +3665,9 @@ impl Step for TestFloatParse {
     }
 }
 
+/// Runs the tool `src/tools/collect-license-metadata` in `ONLY_CHECK=1` mode,
+/// which verifies that `license-metadata.json` is up-to-date and therefore
+/// running the tool normally would not update anything.
 #[derive(Debug, PartialOrd, Ord, Clone, Hash, PartialEq, Eq)]
 pub struct CollectLicenseMetadata;