internal/testenv: add Executable

Tests commonly use code to get os.Executable value, and some cache the
resulting value.

To reduce code duplication, add a helper that does just that.

Change-Id: I9dd7eb24e24a3abd92be2b87227e823f0fca5cb3
Reviewed-on: https://go-review.googlesource.com/c/go/+/609301
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/src/internal/testenv/exec.go b/src/internal/testenv/exec.go
index ebb70a1375..0e6a5f9a1a 100644
--- a/src/internal/testenv/exec.go
+++ b/src/internal/testenv/exec.go
@@ -62,7 +62,7 @@ var tryExec = sync.OnceValue(func() error {
 
 	// We know that this is a test executable. We should be able to run it with a
 	// no-op flag to check for overall exec support.
-	exe, err := os.Executable()
+	exe, err := exePath()
 	if err != nil {
 		return fmt.Errorf("can't probe for exec support: %w", err)
 	}
@@ -71,6 +71,24 @@ var tryExec = sync.OnceValue(func() error {
 	return cmd.Run()
 })
 
+// Executable is a wrapper around [MustHaveExec] and [os.Executable].
+// It returns the path name for the executable that started the current process,
+// or skips the test if the current system can't start new processes,
+// or fails the test if the path can not be obtained.
+func Executable(t testing.TB) string {
+	MustHaveExec(t)
+
+	exe, err := exePath()
+	if err != nil {
+		t.Fatalf("os.Executable error: %v", err)
+	}
+	return exe
+}
+
+var exePath = sync.OnceValues(func() (string, error) {
+	return os.Executable()
+})
+
 var execPaths sync.Map // path -> error
 
 // MustHaveExecPath checks that the current system can start the named executable