Auto merge of #9206 - ehuss:testsuite-rustup, r=Eh2406

testsuite: Improve performance when using rustup.

The rustup wrapper adds a considerable amount of overhead when running processes like `rustc`.  This overrides `PATH` when running the testsuite to prioritize the actual executables to avoid the wrapper.

I'm not 100% confident this won't break something somewhere, but it seems like it should be safe.

In my tests, this makes the testsuite 1.5 to 1.7 times faster.

crates/cargo-test-support/src/lib.rs

@@ -1582,6 +1582,16 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
  p.env_remove(&k);
  }
  }
+ if env::var_os("RUSTUP_TOOLCHAIN").is_some() {
+ // Override the PATH to avoid executing the rustup wrapper thousands
+ // of times. This makes the testsuite run substantially faster.
+ let path = env::var_os("PATH").unwrap_or_default();
+ let paths = env::split_paths(&path);
+ let mut outer_cargo = PathBuf::from(env::var_os("CARGO").unwrap());
+ outer_cargo.pop();
+ let new_path = env::join_paths(std::iter::once(outer_cargo).chain(paths)).unwrap();
+ p.env("PATH", new_path);
+ }
 
  p.cwd(&paths::root())
  .env("HOME", paths::home())

tests/testsuite/old_cargos.rs

@@ -19,7 +19,7 @@ use semver::Version;
 use std::fs;
 
 fn tc_process(cmd: &str, toolchain: &str) -> ProcessBuilder {
- if toolchain == "this" {
+ let mut p = if toolchain == "this" {
  if cmd == "cargo" {
  process(&cargo_exe())
  } else {
@@ -29,7 +29,10 @@ fn tc_process(cmd: &str, toolchain: &str) -> ProcessBuilder {
  let mut cmd = process(cmd);
  cmd.arg(format!("+{}", toolchain));
  cmd
- }
+ };
+ // Reset PATH since `process` modifies it to remove rustup.
+ p.env("PATH", std::env::var_os("PATH").unwrap());
+ p
 }
 
 /// Returns a sorted list of all toolchains.