Rollup merge of rust-lang#146155 - Shourya742:2025-09-03-make-test-run-parallel, r=Kobzol

Make bootstrap self test parallel

This PR refactors the bootstrap self test:

1. Replaced the hardcoded --test-threads=1 with std::thread::available_parallelism(), allowing tests to run with the maximum concurrency supported by the system.
2. Replaced custom hacks around OUT_DIR with TempDir and introduced TestCtx to simplify configuration setup.

r? `@Kobzol`

Author: Zalathar

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

@@ -3326,9 +3326,7 @@ impl Step for Bootstrap {
             .env("INSTA_WORKSPACE_ROOT", &builder.src)
             .env("RUSTC_BOOTSTRAP", "1");
 
-        // bootstrap tests are racy on directory creation so just run them one at a time.
-        // Since there's not many this shouldn't be a problem.
-        run_cargo_test(cargo, &["--test-threads=1"], &[], None, host, builder);
+        run_cargo_test(cargo, &[], &[], None, host, builder);
     }
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {

src/bootstrap/src/core/builder/tests.rs

@@ -10,8 +10,8 @@ use crate::core::build_steps::doc::DocumentationFormat;
 use crate::core::config::Config;
 use crate::utils::cache::ExecutedStep;
 use crate::utils::helpers::get_host_target;
-use crate::utils::tests::ConfigBuilder;
 use crate::utils::tests::git::{GitCtx, git_test};
+use crate::utils::tests::{ConfigBuilder, TestCtx};
 
 static TEST_TRIPLE_1: &str = "i686-unknown-haiku";
 static TEST_TRIPLE_2: &str = "i686-unknown-hurd-gnu";
@@ -22,38 +22,13 @@ fn configure(cmd: &str, host: &[&str], target: &[&str]) -> Config {
 }
 
 fn configure_with_args(cmd: &[&str], host: &[&str], target: &[&str]) -> Config {
-    let cmd = cmd.iter().copied().map(String::from).collect::<Vec<_>>();
-    let mut config = Config::parse(Flags::parse(&cmd));
-    // don't save toolstates
-    config.save_toolstates = None;
-    config.set_dry_run(DryRun::SelfCheck);
-
-    // Ignore most submodules, since we don't need them for a dry run, and the
-    // tests run much faster without them.
-    //
-    // The src/doc/book submodule is needed because TheBook step tries to
-    // access files even during a dry-run (may want to consider just skipping
-    // that in a dry run).
-    let submodule_build = Build::new(Config {
-        // don't include LLVM, so CI doesn't require ninja/cmake to be installed
-        rust_codegen_backends: vec![],
-        ..Config::parse(Flags::parse(&["check".to_owned()]))
-    });
-    submodule_build.require_submodule("src/doc/book", None);
-    config.submodules = Some(false);
-
-    config.ninja_in_file = false;
-    // try to avoid spurious failures in dist where we create/delete each others file
-    // HACK: rather than pull in `tempdir`, use the one that cargo has conveniently created for us
-    let dir = Path::new(env!("OUT_DIR"))
-        .join("tmp-rustbuild-tests")
-        .join(&thread::current().name().unwrap_or("unknown").replace(":", "-"));
-    t!(fs::create_dir_all(&dir));
-    config.out = dir;
-    config.host_target = TargetSelection::from_user(TEST_TRIPLE_1);
-    config.hosts = host.iter().map(|s| TargetSelection::from_user(s)).collect();
-    config.targets = target.iter().map(|s| TargetSelection::from_user(s)).collect();
-    config
+    TestCtx::new()
+        .config(cmd[0])
+        .args(&cmd[1..])
+        .hosts(host)
+        .targets(target)
+        .args(&["--build", TEST_TRIPLE_1])
+        .create_config()
 }
 
 fn first<A, B>(v: Vec<(A, B)>) -> Vec<A> {
@@ -547,8 +522,8 @@ mod snapshot {
 
     use crate::core::build_steps::{compile, dist, doc, test, tool};
     use crate::core::builder::tests::{
-        RenderConfig, TEST_TRIPLE_1, TEST_TRIPLE_2, TEST_TRIPLE_3, configure, configure_with_args,
-        first, host_target, render_steps, run_build,
+        RenderConfig, TEST_TRIPLE_1, TEST_TRIPLE_2, TEST_TRIPLE_3, configure, first, host_target,
+        render_steps, run_build,
     };
     use crate::core::builder::{Builder, Kind, StepDescription, StepMetadata};
     use crate::core::config::TargetSelection;

src/bootstrap/src/utils/cc_detect/tests.rs

@@ -3,7 +3,8 @@ use std::{env, iter};
 
 use super::*;
 use crate::core::config::{Target, TargetSelection};
-use crate::{Build, Config, Flags};
+use crate::utils::tests::TestCtx;
+use crate::{Build, Config, Flags, t};
 
 #[test]
 fn test_ndk_compiler_c() {
@@ -68,7 +69,8 @@ fn test_language_clang() {
 
 #[test]
 fn test_new_cc_build() {
-    let build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let build = Build::new(config);
     let target = TargetSelection::from_user("x86_64-unknown-linux-gnu");
     let cfg = new_cc_build(&build, target.clone());
     let compiler = cfg.get_compiler();
@@ -77,7 +79,8 @@ fn test_new_cc_build() {
 
 #[test]
 fn test_default_compiler_wasi() {
-    let mut build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let mut build = Build::new(config);
     let target = TargetSelection::from_user("wasm32-wasi");
     let wasi_sdk = PathBuf::from("/wasi-sdk");
     build.wasi_sdk_path = Some(wasi_sdk.clone());
@@ -98,7 +101,8 @@ fn test_default_compiler_wasi() {
 
 #[test]
 fn test_default_compiler_fallback() {
-    let build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let build = Build::new(config);
     let target = TargetSelection::from_user("x86_64-unknown-linux-gnu");
     let mut cfg = cc::Build::new();
     let result = default_compiler(&mut cfg, Language::C, target, &build);
@@ -107,7 +111,8 @@ fn test_default_compiler_fallback() {
 
 #[test]
 fn test_find_target_with_config() {
-    let mut build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let mut build = Build::new(config);
     let target = TargetSelection::from_user("x86_64-unknown-linux-gnu");
     let mut target_config = Target::default();
     target_config.cc = Some(PathBuf::from("dummy-cc"));
@@ -128,7 +133,8 @@ fn test_find_target_with_config() {
 
 #[test]
 fn test_find_target_without_config() {
-    let mut build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let mut build = Build::new(config);
     let target = TargetSelection::from_user("x86_64-unknown-linux-gnu");
     build.config.target_config.clear();
     fill_target_compiler(&mut build, target.clone());
@@ -141,7 +147,8 @@ fn test_find_target_without_config() {
 
 #[test]
 fn test_find() {
-    let mut build = Build::new(Config { ..Config::parse(Flags::parse(&["build".to_owned()])) });
+    let config = TestCtx::new().config("build").create_config();
+    let mut build = Build::new(config);
     let target1 = TargetSelection::from_user("x86_64-unknown-linux-gnu");
     let target2 = TargetSelection::from_user("x86_64-unknown-openbsd");
     build.targets.push(target1.clone());