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>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/cmd/api/goapi_test.go b/src/cmd/api/goapi_test.go
index eaccc5ceb5..24620a94af 100644
--- a/src/cmd/api/goapi_test.go
+++ b/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)
+		}
+	}
+}