Refactor single-input config path normalization helpers

internal/config/config.go

@@ -212,11 +212,8 @@ func NewMergeConfig(opts MergeOptions) (Config, error) {
 
 // NewTrimConfig validates raw trim options and returns normalized config.
 func NewTrimConfig(opts TrimOptions) (TrimConfig, error) {
-	inputFile := filepath.Clean(strings.TrimSpace(opts.InputFile))
-	if strings.TrimSpace(opts.InputFile) == "" {
-		return TrimConfig{}, errors.New("--input-file is required")
-	}
-	if err := requireFile(inputFile, "--input-file"); err != nil {
+	inputFile, err := normalizeSingleInputFile(opts.InputFile, "--input-file")
+	if err != nil {
 		return TrimConfig{}, err
 	}
 
@@ -225,12 +222,9 @@ func NewTrimConfig(opts TrimOptions) (TrimConfig, error) {
 		return TrimConfig{}, err
 	}
 
-	reportFile := ""
-	if strings.TrimSpace(opts.ReportFile) != "" {
-		reportFile, err = normalizeOutputPath(opts.ReportFile, "--report-file")
-		if err != nil {
-			return TrimConfig{}, err
-		}
+	reportFile, err := normalizeOptionalOutputPath(opts.ReportFile, "--report-file")
+	if err != nil {
+		return TrimConfig{}, err
 	}
 
 	keep := strings.TrimSpace(opts.Keep)
@@ -269,11 +263,8 @@ func NewTrimConfig(opts TrimOptions) (TrimConfig, error) {
 
 // NewNormalizeConfig validates raw normalize options and returns normalized config.
 func NewNormalizeConfig(opts NormalizeOptions) (NormalizeConfig, error) {
-	inputFile := filepath.Clean(strings.TrimSpace(opts.InputFile))
-	if strings.TrimSpace(opts.InputFile) == "" {
-		return NormalizeConfig{}, errors.New("--input-file is required")
-	}
-	if err := requireFile(inputFile, "--input-file"); err != nil {
+	inputFile, err := normalizeSingleInputFile(opts.InputFile, "--input-file")
+	if err != nil {
 		return NormalizeConfig{}, err
 	}
 
@@ -282,12 +273,9 @@ func NewNormalizeConfig(opts NormalizeOptions) (NormalizeConfig, error) {
 		return NormalizeConfig{}, err
 	}
 
-	reportFile := ""
-	if strings.TrimSpace(opts.ReportFile) != "" {
-		reportFile, err = normalizeOutputPath(opts.ReportFile, "--report-file")
-		if err != nil {
-			return NormalizeConfig{}, err
-		}
+	reportFile, err := normalizeOptionalOutputPath(opts.ReportFile, "--report-file")
+	if err != nil {
+		return NormalizeConfig{}, err
 	}
 
 	outputSchema, err := resolveOutputSchema(opts.OutputSchema)
@@ -383,6 +371,26 @@ func normalizeInputFiles(paths []string) ([]string, error) {
 	return normalized, nil
 }
 
+func normalizeSingleInputFile(path string, flag string) (string, error) {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return "", fmt.Errorf("%s is required", flag)
+	}
+
+	clean := filepath.Clean(path)
+	if err := requireFile(clean, flag); err != nil {
+		return "", err
+	}
+	return clean, nil
+}
+
+func normalizeOptionalOutputPath(path string, flag string) (string, error) {
+	if strings.TrimSpace(path) == "" {
+		return "", nil
+	}
+	return normalizeOutputPath(path, flag)
+}
+
 func normalizeOutputPath(path string, flag string) (string, error) {
 	path = strings.TrimSpace(path)
 	if path == "" {

internal/config/config_test.go

@@ -692,6 +692,25 @@ func TestNewTrimConfigAcceptsOutputSchemaOverride(t *testing.T) {
 	}
 }
 
+func TestNewTrimConfigTreatsWhitespaceReportFileAsOmitted(t *testing.T) {
+	dir := t.TempDir()
+	input := writeTempFile(t, dir, "input.json")
+	output := filepath.Join(dir, "trimmed.json")
+
+	cfg, err := NewTrimConfig(TrimOptions{
+		InputFile:  input,
+		OutputFile: output,
+		Keep:       "1",
+		ReportFile: "  \t  ",
+	})
+	if err != nil {
+		t.Fatalf("config failed: %v", err)
+	}
+	if cfg.ReportFile != "" {
+		t.Fatalf("report file = %q, want empty", cfg.ReportFile)
+	}
+}
+
 func TestNewTrimConfigRejectsInvalidOutputSchemaOverride(t *testing.T) {
 	dir := t.TempDir()
 	input := writeTempFile(t, dir, "input.json")
@@ -812,6 +831,25 @@ func TestNewNormalizeConfigRejectsUnknownOutputModule(t *testing.T) {
 	}
 }
 
+func TestNewNormalizeConfigTreatsWhitespaceReportFileAsOmitted(t *testing.T) {
+	dir := t.TempDir()
+	input := writeTempFile(t, dir, "input.json")
+	output := filepath.Join(dir, "normalized.json")
+
+	cfg, err := NewNormalizeConfig(NormalizeOptions{
+		InputFile:     input,
+		OutputFile:    output,
+		ReportFile:    "\n\t ",
+		OutputModules: DefaultOutputModules,
+	})
+	if err != nil {
+		t.Fatalf("config failed: %v", err)
+	}
+	if cfg.ReportFile != "" {
+		t.Fatalf("report file = %q, want empty", cfg.ReportFile)
+	}
+}
+
 func assertPositiveFloatEnvValidation(t *testing.T, envName string) {
 	t.Helper()