tpl/internal: Sync go_templates

Closes #10411

tpl/internal/go_templates/testenv/exec.go

@@ -0,0 +1,73 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testenv
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// HasExec reports whether the current system can start new processes
+// using os.StartProcess or (more commonly) exec.Command.
+func HasExec() bool {
+	switch runtime.GOOS {
+	case "js", "ios":
+		return false
+	}
+	return true
+}
+
+// MustHaveExec checks that the current system can start new processes
+// using os.StartProcess or (more commonly) exec.Command.
+// If not, MustHaveExec calls t.Skip with an explanation.
+func MustHaveExec(t testing.TB) {
+	if !HasExec() {
+		t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+}
+
+var execPaths sync.Map // path -> error
+
+// MustHaveExecPath checks that the current system can start the named executable
+// using os.StartProcess or (more commonly) exec.Command.
+// If not, MustHaveExecPath calls t.Skip with an explanation.
+func MustHaveExecPath(t testing.TB, path string) {
+	MustHaveExec(t)
+
+	err, found := execPaths.Load(path)
+	if !found {
+		_, err = exec.LookPath(path)
+		err, _ = execPaths.LoadOrStore(path, err)
+	}
+	if err != nil {
+		t.Skipf("skipping test: %s: %s", path, err)
+	}
+}
+
+// CleanCmdEnv will fill cmd.Env with the environment, excluding certain
+// variables that could modify the behavior of the Go tools such as
+// GODEBUG and GOTRACEBACK.
+func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
+	if cmd.Env != nil {
+		panic("environment already set")
+	}
+	for _, env := range os.Environ() {
+		// Exclude GODEBUG from the environment to prevent its output
+		// from breaking tests that are trying to parse other command output.
+		if strings.HasPrefix(env, "GODEBUG=") {
+			continue
+		}
+		// Exclude GOTRACEBACK for the same reason.
+		if strings.HasPrefix(env, "GOTRACEBACK=") {
+			continue
+		}
+		cmd.Env = append(cmd.Env, env)
+	}
+	return cmd
+}