Preserve existing model files when not using --clean

gen.go

@@ -92,27 +92,17 @@ func ConnectDSN(dsn string) (*gorm.DB, error) {
 // It cleans the output directory (if Clean is true), generates models using gorm.io/gen,
 // and appends <Model>Cols variables with type-safe Field descriptors.
 func (m *GormGen) GenModels(ctx context.Context) error {
-	dir := m.cfg.OutputDir
-	if !strings.HasPrefix(dir, "./") {
-		dir = "./" + dir
-	}
-	absDir, err := filepath.Abs(dir)
-	if err != nil {
-		return err
-	}
-
-	// When Clean is false, backup existing files first.
-	var backupDir string
-	if !m.cfg.Clean {
-		backupDir, err = m.backupDir(absDir)
-		if err != nil {
-			return fmt.Errorf("failed to backup existing files: %w", err)
+	// Clean output directory if Clean is true.
+	if m.cfg.Clean {
+		if err := m.cleanOutputDir(); err != nil {
+			return fmt.Errorf("failed to clean output dir: %w", err)
 		}
-		defer os.RemoveAll(backupDir)
 	}
 
-	if err := m.cleanOutputDir(); err != nil {
-		return fmt.Errorf("failed to clean output dir: %w", err)
+	// When Clean is false, save existing files to restore later.
+	var existingFiles map[string][]byte
+	if !m.cfg.Clean {
+		existingFiles = m.saveExistingFiles()
 	}
 
 	g := gen.NewGenerator(gen.Config{
@@ -164,11 +154,9 @@ func (m *GormGen) GenModels(ctx context.Context) error {
 		return fmt.Errorf("failed to cleanup generated files: %w", err)
 	}
 
-	// Restore backup if Clean was false.
-	if backupDir != "" {
-		if err := m.restoreBackup(absDir, backupDir); err != nil {
-			return fmt.Errorf("failed to restore backup: %w", err)
-		}
+	// Restore existing files that were not regenerated.
+	if !m.cfg.Clean {
+		m.restoreExistingFiles(existingFiles)
 	}
 
 	if err := m.generateCols(); err != nil {
@@ -178,75 +166,51 @@ func (m *GormGen) GenModels(ctx context.Context) error {
 	return nil
 }
 
-// backupDir creates a backup copy of the directory and returns the backup path.
-func (m *GormGen) backupDir(dir string) (string, error) {
-	backupPath := dir + ".backup"
-	if _, err := os.Stat(backupPath); err == nil {
-		os.RemoveAll(backupPath)
+// saveExistingFiles saves the content of existing .go files in the output directory.
+func (m *GormGen) saveExistingFiles() map[string][]byte {
+	dir := m.cfg.OutputDir
+	if !strings.HasPrefix(dir, "./") {
+		dir = "./" + dir
 	}
 
-	if err := copyDir(dir, backupPath); err != nil {
-		return "", err
+	files := make(map[string][]byte)
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return files
 	}
-	fmt.Printf("Backed up: %s -> %s\n", dir, backupPath)
-	return backupPath, nil
+
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".go") {
+			continue
+		}
+		path := filepath.Join(dir, entry.Name())
+		if data, err := os.ReadFile(path); err == nil {
+			files[entry.Name()] = data
+		}
+	}
+	return files
 }
 
-// restoreBackup restores files from backup that don't exist in the target directory.
-func (m *GormGen) restoreBackup(dir, backupDir string) error {
-	entries, err := os.ReadDir(backupDir)
-	if err != nil {
-		return err
+// restoreExistingFiles restores files that weren't regenerated.
+func (m *GormGen) restoreExistingFiles(saved map[string][]byte) {
+	dir := m.cfg.OutputDir
+	if !strings.HasPrefix(dir, "./") {
+		dir = "./" + dir
 	}
 
 	restored := 0
-	for _, entry := range entries {
-		if entry.IsDir() {
-			continue
-		}
-		targetPath := filepath.Join(dir, entry.Name())
-		if _, err := os.Stat(targetPath); os.IsNotExist(err) {
-			srcPath := filepath.Join(backupDir, entry.Name())
-			data, err := os.ReadFile(srcPath)
-			if err != nil {
-				continue
+	for name, data := range saved {
+		path := filepath.Join(dir, name)
+		if _, err := os.Stat(path); os.IsNotExist(err) {
+			if err := os.WriteFile(path, data, 0644); err == nil {
+				fmt.Printf("Restored: %s\n", path)
+				restored++
 			}
-			if err := os.WriteFile(targetPath, data, 0644); err != nil {
-				return err
-			}
-			fmt.Printf("Restored: %s\n", targetPath)
-			restored++
 		}
 	}
 	if restored > 0 {
-		fmt.Printf("Restored %d files from backup\n", restored)
+		fmt.Printf("Restored %d existing files\n", restored)
 	}
-	return nil
-}
-
-// copyDir copies a directory recursively.
-func copyDir(src, dst string) error {
-	return filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-		rel, _ := filepath.Rel(src, path)
-		dstPath := filepath.Join(dst, rel)
-
-		if info.IsDir() {
-			return os.MkdirAll(dstPath, info.Mode())
-		}
-		return copyFile(path, dstPath)
-	})
-}
-
-// copyFile copies a single file.
-func copyFile(src, dst string) error {
-	data, err := os.ReadFile(src)
-	if err != nil {
-		return err
-	}
-	return os.WriteFile(dst, data, 0644)
 }
 
 // cleanOutputDir removes existing .go files from the output directory
@@ -270,11 +234,6 @@ func (m *GormGen) cleanOutputDir() error {
 		return nil
 	}
 
-	// Skip cleaning if Clean is false.
-	if !m.cfg.Clean {
-		return nil
-	}
-
 	entries, err := os.ReadDir(absDir)
 	if err != nil {
 		return err