cmd/go: make TestNewReleaseRebuildsStalePackagesInGOPATH pass again

The test TestNewReleaseRebuildsStalePackagesInGOPATH is not run in
short mode, so people tend to not notice when it fails. It was failing
due to the build cache. Make it pass again by 1) changing it to modify
the package in a way visible to the compiler, so that the change is
not hidden by caching; 2) accepting "not installed but available in
build cache" as always being a valid reason for a stale package, as go
list does not try to figure out an underlying reason for why a package
is stale when it finds it in the build cache but not installed.

Updates #24436

Change-Id: Iaeaa298f153451ec913a653dd4e6da79a33055bb
Reviewed-on: https://go-review.googlesource.com/123815
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 7b7f1ccb1b0e17454ec265f8105086d532196773..6f5e0c86a961a49e0a7e956bca7459765b2f323d 100644 (file)
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -751,7 +751,11 @@ func (tg *testgoData) wantStale(pkg, reason, msg string) {
        if !stale {
                tg.t.Fatal(msg)
        }
-       if reason == "" && why != "" || !strings.Contains(why, reason) {
+       // We always accept the reason as being "not installed but
+       // available in build cache", because when that is the case go
+       // list doesn't try to sort out the underlying reason why the
+       // package is not installed.
+       if reason == "" && why != "" || !strings.Contains(why, reason) && !strings.Contains(why, "not installed but available in build cache") {
                tg.t.Errorf("wrong reason for Stale=true: %q, want %q", why, reason)
        }
 }
@@ -881,13 +885,13 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
        tg := testgo(t)
        defer tg.cleanup()
 
-       addNL := func(name string) (restore func()) {
+       addVar := func(name string, idx int) (restore func()) {
                data, err := ioutil.ReadFile(name)
                if err != nil {
                        t.Fatal(err)
                }
                old := data
-               data = append(data, '\n')
+               data = append(data, fmt.Sprintf("var DummyUnusedVar%d bool\n", idx)...)
                if err := ioutil.WriteFile(name, append(data, '\n'), 0666); err != nil {
                        t.Fatal(err)
                }
@@ -911,19 +915,19 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
        // In fact this should be true even outside a release branch.
        sys := runtime.GOROOT() + "/src/runtime/internal/sys/sys.go"
        tg.sleep()
-       restore := addNL(sys)
+       restore := addVar(sys, 0)
        restore()
        tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, after updating mtime of runtime/internal/sys/sys.go")
 
        // But changing content of any file should have an effect.
        // Previously zversion.go was the only one that mattered;
        // now they all matter, so keep using sys.go.
-       restore = addNL(sys)
+       restore = addVar(sys, 1)
        defer restore()
        tg.wantStale("p1", "stale dependency: runtime/internal/sys", "./testgo list claims p1 is NOT stale, incorrectly, after changing sys.go")
        restore()
        tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, after changing back to old release")
-       addNL(sys)
+       addVar(sys, 2)
        tg.wantStale("p1", "stale dependency: runtime/internal/sys", "./testgo list claims p1 is NOT stale, incorrectly, after changing sys.go again")
        tg.run("install", "-i", "p1")
        tg.wantNotStale("p1", "", "./testgo list claims p1 is stale after building with new release")