test(pgo): determine llvm-profdata existence at compile time

.github/workflows/main.yml

@@ -163,6 +163,9 @@ jobs:
     - run: rustup target add ${{ matrix.other }}
     - run: rustup component add rustc-dev llvm-tools-preview rust-docs
       if: startsWith(matrix.rust, 'nightly')
+    - name: Append rustup toolchain target bins to PATH
+      run: echo "$(dirname $(rustc --print target-libdir))/bin" >> "$GITHUB_PATH"
+      if: matrix.os == 'ubuntu-latest'
     - run: sudo apt update -y && sudo apt install lldb gcc-multilib libsecret-1-0 libsecret-1-dev -y
       if: matrix.os == 'ubuntu-latest'
     - run: rustup component add rustfmt || echo "rustfmt not available"

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

@@ -326,19 +326,30 @@ fn check_command(command_path: &Path, args: &[&str]) -> Result<(), CheckCommandE
 }
 
 fn has_command(command: &str) -> bool {
-    match check_command(Path::new(command), &["--version"]).as_ref() {
-        Ok(()) => true,
-        Err(e @ CheckCommandError::CannotExecute { program, .. }) => {
-            // * hg is not installed on GitHub macOS or certain constrained
-            //   environments like Docker. Consider installing it if Cargo
-            //   gains more hg support, but otherwise it isn't critical.
-            // * lldb is not pre-installed on Ubuntu and Windows, so skip.
-            if is_ci() && !matches!(program.as_str(), "hg" | "lldb") {
-                panic!("{e}")
+    let cmd = Path::new(command);
+    let mut err = None;
+    for arg in ["--version", "-h"] {
+        match check_command(cmd, &[arg]) {
+            Ok(()) => return true,
+            Err(e) => {
+                err = Some(e);
             }
+        }
+    }
+
+    match err.unwrap() {
+        // Always bail out if a command is not found on CI, except:
+        //
+        // * hg is not installed on GitHub macOS or certain constrained
+        //   environments like Docker. Consider installing it if Cargo
+        //   gains more hg support, but otherwise it isn't critical.
+        // * lldb is not pre-installed on Ubuntu and Windows, so skip.
+        CheckCommandError::CannotExecute { program, .. }
+            if !is_ci() || matches!(program.as_str(), "hg" | "lldb") =>
+        {
             false
         }
-        Err(e @ CheckCommandError::UnsuccessfulTermination { .. }) => {
+        e => {
             panic!("{e}");
         }
     }

tests/testsuite/pgo.rs

@@ -1,36 +1,14 @@
 //! Test if PGO works.
 
-use std::path::PathBuf;
-use std::process::Command;
-
 use cargo_test_support::prelude::*;
 use cargo_test_support::project;
 use cargo_test_support::str;
 
-fn llvm_profdata() -> Option<PathBuf> {
-    let output = Command::new("rustc")
-        .arg("--print=target-libdir")
-        .output()
-        .expect("rustc to run");
-    assert!(output.status.success());
-    let mut libdir = PathBuf::from(String::from_utf8(output.stdout).unwrap());
-    assert!(libdir.pop());
-    let mut bin = libdir.join("bin").join("llvm-profdata");
-    bin.exists().then(|| bin.clone()).or_else(|| {
-        bin.set_extension("exe");
-        bin.exists().then_some(bin)
-    })
-}
-
-#[cargo_test]
 // macOS may emit different LLVM PGO warnings.
 // Windows LLVM has different requirements.
-#[cfg_attr(not(target_os = "linux"), ignore = "linux only")]
+#[cfg_attr(not(target_os = "linux"), cargo_test, ignore = "linux only")]
+#[cfg_attr(target_os = "linux", cargo_test(requires = "llvm-profdata"))]
 fn pgo_works() {
-    let Some(llvm_profdata) = llvm_profdata() else {
-        return;
-    };
-
     let p = project()
         .file(
             "Cargo.toml",
@@ -77,7 +55,7 @@ fn pgo_works() {
         .with_process_builder(cargo_test_support::process(release_bin))
         .run();
 
-    cargo_test_support::process(llvm_profdata)
+    cargo_test_support::process("llvm-profdata")
         .arg("merge")
         .arg("-o")
         .arg(&profdata_path)