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 <[email protected]>
Run-TryBot: Bryan C. Mills <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Jay Conrod <[email protected]>

src/cmd/go/testdata/script/cgo_stale.txt

@@ -0,0 +1,39 @@
+# golang.org/issue/46347: a stale runtime/cgo should only force a single rebuild
+
+[!cgo] skip
+[short] skip
+
+
+# If we set a unique CGO_CFLAGS, the installed copy of runtime/cgo
+# should be reported as stale.
+
+env CGO_CFLAGS=-DTestScript_cgo_stale=true
+stale runtime/cgo
+
+
+# If we then build a package that uses cgo, runtime/cgo should be rebuilt and
+# cached with the new flag, but not installed to GOROOT (and thus still stale).
+
+env GOCACHE=$WORK/cache  # Use a fresh cache to avoid interference between runs.
+
+go build -x .
+stderr '[/\\]cgo'$GOEXE'["]? .* -importpath runtime/cgo'
+stale runtime/cgo
+
+
+# After runtime/cgo has been rebuilt and cached, it should not be rebuilt again
+# even though it is still reported as stale.
+
+go build -x .
+! stderr '[/\\]cgo'$GOEXE'["]? .* -importpath runtime/cgo'
+stale runtime/cgo
+
+
+-- go.mod --
+module example.com/m
+
+go 1.17
+-- m.go --
+package m
+
+import "C"

src/cmd/go/testdata/script/list_std_vendor.txt

@@ -0,0 +1,32 @@
+# https://golang.org/issue/44725: packages in std should have the same
+# dependencies regardless of whether they are listed from within or outside
+# GOROOT/src.
+
+# Control case: net, viewed from outside the 'std' module,
+# should depend on vendor/golang.org/… instead of golang.org/….
+
+go list -deps net
+stdout '^vendor/golang.org/x/net'
+! stdout '^golang.org/x/net'
+cp stdout $WORK/net-deps.txt
+
+
+# It should still report the same package dependencies when viewed from
+# within GOROOT/src.
+
+cd $GOROOT/src
+
+go list -deps net
+stdout '^vendor/golang.org/x/net'
+! stdout '^golang.org/x/net'
+cmp stdout $WORK/net-deps.txt
+
+
+# However, 'go mod' and 'go get' subcommands should report the original module
+# dependencies, not the vendored packages.
+
+[!net] stop
+
+env GOPROXY=
+go mod why -m golang.org/x/net
+stdout '^# golang.org/x/net\nnet\ngolang.org/x/net'

src/cmd/go/testdata/script/test_race_install_cgo.txt

@@ -2,8 +2,6 @@
 
 [!race] skip
 
-[!darwin] ! stale cmd/cgo  # The darwin builders are spuriously stale; see #33598.
-
 env GOBIN=$WORK/bin
 go install m/mtime m/sametime
 

src/cmd/go/testdata/script/toolexec.txt

@@ -3,6 +3,12 @@
 # Build our simple toolexec program.
 go build ./cmd/mytool
 
+# Use an ephemeral build cache so that our toolexec output is not cached
+# for any stale standard-library dependencies.
+#
+# TODO(#27628): This should not be necessary.
+env GOCACHE=$WORK/gocache
+
 # Build the main package with our toolexec program. For each action, it will
 # print the tool's name and the TOOLEXEC_IMPORTPATH value. We expect to compile
 # each package once, and link the main package once.

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)