Fix failed to symlink overlay files if it already exists

cmd/vinegar/binary_setup.go

@@ -59,8 +59,8 @@ func (b *Binary) Setup() error {
 		return fmt.Errorf("apply fflags: %w", err)
 	}
 
-	if err := dirs.OverlayDir(b.Dir); err != nil {
-		return fmt.Errorf("overlay dir: %w", err)
+	if err := dirs.OverlayDir(dirs.Overlay, b.Dir); err != nil {
+		return err
 	}
 
 	if err := b.SetupDxvk(); err != nil {

internal/dirs/copy.go

@@ -2,14 +2,41 @@ package dirs
 
 import (
 	"errors"
-	"log/slog"
 	"os"
 
+	"log/slog"
+	"path/filepath"
+
 	cp "github.com/otiai10/copy"
 )
 
-func OverlayDir(dir string) error {
-	_, err := os.Stat(Overlay)
+func CompareLink(src, dest string) (bool, error) {
+	info, err := os.Stat(src)
+	if err != nil {
+		return false, err
+	}
+
+	if info.Mode()&os.ModeSymlink != 0 {
+		srcSymPath, err := filepath.EvalSymlinks(src)
+		if err != nil {
+			return false, err
+		}
+
+		destSymPath, err := filepath.EvalSymlinks(dest)
+		if err != nil {
+			return false, err
+		}
+
+		if destSymPath != srcSymPath {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
+
+func OverlayDir(overlay, dir string) error {
+	_, err := os.Stat(overlay)
 	if errors.Is(err, os.ErrNotExist) {
 		return nil
 	} else if err != nil {
@@ -18,5 +45,20 @@ func OverlayDir(dir string) error {
 
 	slog.Info("Copying Overlay directory's files", "dir", dir)
 
-	return cp.Copy(Overlay, dir)
+	return cp.Copy(overlay, dir, cp.Options{
+		Sync: true,
+		PreserveOwner: true,
+		PreserveTimes: true,
+		Skip: func(info os.FileInfo, src, dest string) (bool, error) {
+			if info.IsDir() {
+				return false, nil
+			}
+
+			if res, err := CompareLink(src, dest); err == nil && res {
+				return true, nil
+			}
+
+			return false, nil
+		},
+	})
 }

internal/dirs/copy_test.go

@@ -0,0 +1,62 @@
+package dirs
+
+import (
+	"os"
+	"testing"
+
+	"path/filepath"
+)
+
+func createTestFile(t *testing.T, overlay, dest string) (string, string) {
+	if err := Mkdirs(filepath.Join(overlay, "content"), filepath.Join(dest, "content")); err != nil {
+		t.Fatal(err)
+	}
+
+	srcPath := filepath.Join(overlay, "content", "test_content.txt")
+	destPath := filepath.Join(dest, "content", "test_content.txt")
+
+	file, err :=  os.OpenFile(srcPath, os.O_CREATE|os.O_WRONLY, 0o755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := file.WriteString("MEOWMEOW TESTING YAHH!!"); err != nil {
+		file.Close()
+		t.Fatal(err)
+	}
+
+	if err := file.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	return srcPath, destPath
+}
+
+func test(t *testing.T, overlay, dest, srcPath, destPath string) {
+	if err := OverlayDir(overlay, dest); err != nil {
+		t.Fatal(err)
+	}
+
+
+	if res, err := CompareLink(srcPath, destPath); err != nil && !res {
+		t.Fatal(err)
+	}
+}
+
+func TestDefault(t *testing.T) {
+	overlay := t.TempDir()
+	dest := t.TempDir()
+
+	srcPath, destPath := createTestFile(t, overlay, dest)
+	test(t, overlay, dest, srcPath, destPath)
+}
+
+func TestAlreadyExists(t *testing.T) {
+	overlay := t.TempDir()
+	dest := t.TempDir()
+
+	srcPath, destPath := createTestFile(t, overlay, dest)
+
+	test(t, overlay, dest, srcPath, destPath)
+	test(t, overlay, dest, srcPath, destPath)
+}