cmd/go: make vet work with -overlay

It never worked before, an apparent oversight.
This will also make tests work, since tests run vet.

The new FIPS mode will use overlays, so this was
keeping go test from working in that mode.

Fixes #44957.

Change-Id: I3a77846b3b3f9a3a53118aaece93ee93214a36a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/629199
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>

Author: rsc

src/cmd/go/internal/work/exec.go

@@ -858,7 +858,7 @@ OverlayLoop:
 		embed.Patterns = p.Internal.Embed
 		embed.Files = make(map[string]string)
 		for _, file := range p.EmbedFiles {
-			embed.Files[file] = filepath.Join(p.Dir, file)
+			embed.Files[file] = fsys.Actual(filepath.Join(p.Dir, file))
 		}
 		js, err := json.MarshalIndent(&embed, "", "\t")
 		if err != nil {
@@ -1175,9 +1175,9 @@ func buildVetConfig(a *Action, srcfiles []string) {
 		ID:           a.Package.ImportPath,
 		Compiler:     cfg.BuildToolchainName,
 		Dir:          a.Package.Dir,
-		GoFiles:      mkAbsFiles(a.Package.Dir, gofiles),
-		NonGoFiles:   mkAbsFiles(a.Package.Dir, nongofiles),
-		IgnoredFiles: mkAbsFiles(a.Package.Dir, ignored),
+		GoFiles:      actualFiles(mkAbsFiles(a.Package.Dir, gofiles)),
+		NonGoFiles:   actualFiles(mkAbsFiles(a.Package.Dir, nongofiles)),
+		IgnoredFiles: actualFiles(mkAbsFiles(a.Package.Dir, ignored)),
 		ImportPath:   a.Package.ImportPath,
 		ImportMap:    make(map[string]string),
 		PackageFile:  make(map[string]string),
@@ -3383,6 +3383,15 @@ func mkAbsFiles(dir string, files []string) []string {
 	return abs
 }
 
+// actualFiles applies fsys.Actual to the list of files.
+func actualFiles(files []string) []string {
+	a := make([]string, len(files))
+	for i, f := range files {
+		a[i] = fsys.Actual(f)
+	}
+	return a
+}
+
 // passLongArgsInResponseFiles modifies cmd such that, for
 // certain programs, long arguments are passed in "response files", a
 // file on disk with the arguments, with one arg per line. An actual

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

@@ -22,6 +22,8 @@ go build -overlay overlay.json -o print_abspath$GOEXE ./printpath
 exec ./print_abspath$GOEXE
 stdout $WORK[/\\]gopath[/\\]src[/\\]m[/\\]printpath[/\\]main.go
 
+go vet -overlay overlay.json ./printpath
+
 go build -overlay overlay.json -o print_trimpath$GOEXE -trimpath ./printpath
 exec ./print_trimpath$GOEXE
 stdout ^m[/\\]printpath[/\\]main.go