cmd/api: omit outside dependencies when listing the packages in "std"

As of CL 251159, when 'go list -deps std' is run within GOROOT/src, it treats the vendored external dependencies as real module dependencies, not standard-library "vendor/" packages (which still exist in that case, but are treated as distinct packages outside the "std" module). Fixes #41358 Updates #30241 Change-Id: Ic23eae9829d90e74a340d49ca9052e9191597410 Reviewed-on: https://go-review.googlesource.com/c/go/+/254738 Run-TryBot: Bryan C. Mills <bcmills@google.com> Trust: Bryan C. Mills <bcmills@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>

Author: Bryan C. Mills

src/cmd/api/goapi.go

@@ -87,7 +87,10 @@ var contexts = []*build.Context{
 func contextName(c *build.Context) string {
 s := c.GOOS + "-" + c.GOARCH
 if c.CgoEnabled {
-return s + "-cgo"
+s += "-cgo"
+}
+if c.Dir != "" {
+s += fmt.Sprintf(" [%s]", c.Dir)
 }
 return s
 }
@@ -478,6 +481,9 @@ func (w *Walker) loadImports() {
 
 cmd := exec.Command(goCmd(), "list", "-e", "-deps", "-json", "std")
 cmd.Env = listEnv(w.context)
+if w.context.Dir != "" {
+cmd.Dir = w.context.Dir
+}
 out, err := cmd.CombinedOutput()
 if err != nil {
 log.Fatalf("loading imports: %v\n%s", err, out)
@@ -491,6 +497,7 @@ func (w *Walker) loadImports() {
 var pkg struct {
 ImportPath, Dir string
 ImportMap map[string]string
+Standard bool
 }
 err := dec.Decode(&pkg)
 if err == io.EOF {
@@ -503,11 +510,13 @@ func (w *Walker) loadImports() {
 // - Package "unsafe" contains special signatures requiring
 // extra care when printing them - ignore since it is not
 // going to change w/o a language change.
-// - internal and vendored packages do not contribute to our
-// API surface.
+// - Internal and vendored packages do not contribute to our
+// API surface. (If we are running within the "std" module,
+// vendored dependencies appear as themselves instead of
+// their "vendor/" standard-library copies.)
 // - 'go list std' does not include commands, which cannot be
 // imported anyway.
-if ip := pkg.ImportPath; ip != "unsafe" && !strings.HasPrefix(ip, "vendor/") && !internalPkg.MatchString(ip) {
+if ip := pkg.ImportPath; pkg.Standard && ip != "unsafe" && !strings.HasPrefix(ip, "vendor/") && !internalPkg.MatchString(ip) {
 stdPackages = append(stdPackages, ip)
 }
 importDir[pkg.ImportPath] = pkg.Dir

src/cmd/api/goapi_test.go

@@ -216,3 +216,16 @@ func TestIssue29837(t *testing.T) {
 }
 }
 }
+
+func TestIssue41358(t *testing.T) {
+context := new(build.Context)
+*context = build.Default
+context.Dir = filepath.Join(context.GOROOT, "src")
+
+w := NewWalker(context, context.Dir)
+for _, pkg := range w.stdPackages {
+if strings.HasPrefix(pkg, "vendor/") || strings.HasPrefix(pkg, "golang.org/x/") {
+t.Fatalf("stdPackages contains unexpected package %s", pkg)
+}
+}
+}

src/cmd/go/internal/modload/load.go

@@ -1106,8 +1106,12 @@ func (ld *loader) stdVendor(parentPath, path string) string {
 // Do the same for importers beginning with the prefix 'vendor/' even if we
 // are *inside* of the 'std' module: the 'vendor/' packages that resolve
 // globally from GOROOT/src/vendor (and are listed as part of 'go list std')
-// are distinct from the real module dependencies, and cannot import internal
-// packages from the real module.
+// are distinct from the real module dependencies, and cannot import
+// internal packages from the real module.
+//
+// (Note that although the 'vendor/' packages match the 'std' *package*
+// pattern, they are not part of the std *module*, and do not affect
+// 'go mod tidy' and similar module commands when working within std.)
 vendorPath := pathpkg.Join("vendor", path)
 if _, err := os.Stat(filepath.Join(cfg.GOROOTsrc, filepath.FromSlash(vendorPath))); err == nil {
 return vendorPath