cmd/go,cmd/link: do not check for staleness in most tests

Instead, check that stale packages in the standard library
are not rebuilt when already present in the build cache,
and are not installed implicitly when rebuilt.

We retain the staleness checks for the runtime package in tests
involving '-i', because those are guaranteed to fail anyway if the
package is stale and the "stale" failure message is arguably clearer.
They can be removed if/when we remove the '-i' flag, but the runtime
package is less likely to become stale because it does not have cgo
dependencies.

Fixes #46347
Updates #33598
Updates #35459
Updates #41696

Change-Id: I7b0a808addd930f9f4911ff53ded62272af75a40
Reviewed-on: https://go-review.googlesource.com/c/go/+/322629
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>

1 files changed, 35 insertions, 17 deletions

diff --git a/src/cmd/link/dwarf_test.go b/src/cmd/link/dwarf_test.go
index 0419613cbe..3ca59bd47f 100644
--- a/src/cmd/link/dwarf_test.go
+++ b/src/cmd/link/dwarf_test.go
@@ -19,6 +19,36 @@ import (
 	"testing"
 )
 
+// TestMain allows this test binary to run as a -toolexec wrapper for the 'go'
+// command. If LINK_TEST_TOOLEXEC is set, TestMain runs the binary as if it were
+// cmd/link, and otherwise runs the requested tool as a subprocess.
+//
+// This allows the test to verify the behavior of the current contents of the
+// cmd/link package even if the installed cmd/link binary is stale.
+func TestMain(m *testing.M) {
+	if os.Getenv("LINK_TEST_TOOLEXEC") == "" {
+		// Not running as a -toolexec wrapper. Just run the tests.
+		os.Exit(m.Run())
+	}
+
+	if strings.TrimSuffix(filepath.Base(os.Args[1]), ".exe") == "link" {
+		// Running as a -toolexec linker, and the tool is cmd/link.
+		// Substitute this test binary for the linker.
+		os.Args = os.Args[1:]
+		main()
+		os.Exit(0)
+	}
+
+	cmd := exec.Command(os.Args[1], os.Args[2:]...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		os.Exit(1)
+	}
+	os.Exit(0)
+}
+
 func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string) {
 	testenv.MustHaveCGO(t)
 	testenv.MustHaveGoBuild(t)
@@ -29,17 +59,6 @@ func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string)
 
 	t.Parallel()
 
-	out, err := exec.Command(testenv.GoToolPath(t), "list", "-f", "{{.Stale}}", "cmd/link").CombinedOutput()
-	if err != nil {
-		t.Fatalf("go list: %v\n%s", err, out)
-	}
-	if string(out) != "false\n" {
-		if strings.HasPrefix(testenv.Builder(), "darwin-") {
-			t.Skipf("cmd/link is spuriously stale on Darwin builders - see #33598")
-		}
-		t.Fatalf("cmd/link is stale - run go install cmd/link")
-	}
-
 	for _, prog := range []string{"testprog", "testprogcgo"} {
 		prog := prog
 		expectDWARF := expectDWARF
@@ -48,11 +67,11 @@ func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string)
 			if extld == "" {
 				extld = "gcc"
 			}
+			var err error
 			expectDWARF, err = cmddwarf.IsDWARFEnabledOnAIXLd(extld)
 			if err != nil {
 				t.Fatal(err)
 			}
-
 		}
 
 		t.Run(prog, func(t *testing.T) {
@@ -62,15 +81,14 @@ func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string)
 
 			exe := filepath.Join(tmpDir, prog+".exe")
 			dir := "../../runtime/testdata/" + prog
-			cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", exe)
+			cmd := exec.Command(testenv.GoToolPath(t), "build", "-toolexec", os.Args[0], "-o", exe)
 			if buildmode != "" {
 				cmd.Args = append(cmd.Args, "-buildmode", buildmode)
 			}
 			cmd.Args = append(cmd.Args, dir)
-			if env != nil {
-				cmd.Env = append(os.Environ(), env...)
-				cmd.Env = append(cmd.Env, "CGO_CFLAGS=") // ensure CGO_CFLAGS does not contain any flags. Issue #35459
-			}
+			cmd.Env = append(os.Environ(), env...)
+			cmd.Env = append(cmd.Env, "CGO_CFLAGS=") // ensure CGO_CFLAGS does not contain any flags. Issue #35459
+			cmd.Env = append(cmd.Env, "LINK_TEST_TOOLEXEC=1")
 			out, err := cmd.CombinedOutput()
 			if err != nil {
 				t.Fatalf("go build -o %v %v: %v\n%s", exe, dir, err, out)