dup symlink if needed

Author: Zxilly

src/cmd/internal/moddeps/moddeps_test.go

@@ -13,6 +13,7 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
+	"runtime"
 	"slices"
 	"sort"
 	"strings"
@@ -217,7 +218,7 @@ func TestAllDependencies(t *testing.T) {
 			}
 			// TODO(golang.org/issue/43440): Check anything else influenced by dependency versions.
 
-			diff, err := testenv.Command(t, "diff", "--recursive", "--no-dereference", "--unified", r.Dir, m.Dir).CombinedOutput()
+			diff, err := testenv.Command(t, "diff", "--recursive", "--unified", r.Dir, m.Dir).CombinedOutput()
 			if err != nil || len(diff) != 0 {
 				t.Errorf(`Module %s in %s is not tidy (-want +got):
 
@@ -284,6 +285,18 @@ func makeGOROOTCopy(t *testing.T) string {
 				return err
 			}
 			perm = info.Mode() & os.ModePerm
+
+			// dup symlink
+			target, err := os.Readlink(src)
+			if err != nil {
+				return err
+			}
+			// create a symlink to the target directory
+			err = os.Symlink(target, dst)
+			if err != nil {
+				return err
+			}
+			return filepath.SkipDir
 		}
 
 		// If it's a directory, make a corresponding directory.
@@ -311,6 +324,9 @@ func makeGOROOTCopy(t *testing.T) string {
 		return d.Close()
 	})
 	if err != nil {
+		if _, ok := err.(*os.LinkError); ok && runtime.GOOS == "windows" {
+			t.Skipf("skipping because of symlink error on Windows: %v", err)
+		}
 		t.Fatal(err)
 	}
 	t.Logf("copied GOROOT from %s to %s", testenv.GOROOT(t), gorootCopyDir)