Expand FormatOutput to accept optional paths for format inference

cmd/bkld/main.go

@@ -45,15 +45,10 @@ See https://bkl.gopatchy.io/#bkld for detailed documentation.`
 	}
 
 	format := ""
-
 	if opts.OutputFormat != nil {
 		format = *opts.OutputFormat
 	}
 
-	if format == "" && opts.OutputPath != nil {
-		format = bkl.Ext(string(*opts.OutputPath))
-	}
-
 	// Prepare paths from current working directory
 	paths := []string{string(opts.Positional.BasePath), string(opts.Positional.TargetPath)}
 	preparedPaths, err := bkl.PreparePathsFromCwd(paths, "/")
@@ -68,16 +63,8 @@ See https://bkl.gopatchy.io/#bkld for detailed documentation.`
 		fatal(err)
 	}
 
-	// Get format from first file if not specified
-	if format == "" {
-		_, f, err := bkl.FileMatch(fsys, preparedPaths[0])
-		if err != nil {
-			fatal(err)
-		}
-		format = f
-	}
-
-	enc, err := bkl.FormatOutput(doc, format)
+	// Pass output path and input path - FormatOutput will use their extensions if format is empty
+	enc, err := bkl.FormatOutput(doc, format, (*string)(opts.OutputPath), &preparedPaths[0])
 	if err != nil {
 		fatal(err)
 	}

cmd/bkli/main.go

@@ -44,15 +44,10 @@ See https://bkl.gopatchy.io/#bkli for detailed documentation.`
 	}
 
 	format := ""
-
 	if opts.OutputFormat != nil {
 		format = *opts.OutputFormat
 	}
 
-	if format == "" && opts.OutputPath != nil {
-		format = bkl.Ext(string(*opts.OutputPath))
-	}
-
 	// Convert paths to strings
 	paths := make([]string, len(opts.Positional.InputPaths))
 	for i, path := range opts.Positional.InputPaths {
@@ -72,16 +67,8 @@ See https://bkl.gopatchy.io/#bkli for detailed documentation.`
 		fatal(err)
 	}
 
-	// Get format from first file if not specified
-	if format == "" {
-		_, f, err := bkl.FileMatch(fsys, preparedPaths[0])
-		if err != nil {
-			fatal(err)
-		}
-		format = f
-	}
-
-	enc, err := bkl.FormatOutput(doc, format)
+	// Pass output path and input path - FormatOutput will use their extensions if format is empty
+	enc, err := bkl.FormatOutput(doc, format, (*string)(opts.OutputPath), &preparedPaths[0])
 	if err != nil {
 		fatal(err)
 	}

cmd/bklr/main.go

@@ -58,23 +58,12 @@ See https://bkl.gopatchy.io/#bklr for detailed documentation.`
 
 	// Get format from file if not specified
 	format := ""
-	if opts.OutputPath != nil {
-		format = bkl.Ext(string(*opts.OutputPath))
-	}
-
 	if opts.OutputFormat != nil {
 		format = *opts.OutputFormat
 	}
 
-	if format == "" {
-		_, f, err := bkl.FileMatch(fsys, preparedPaths[0])
-		if err != nil {
-			fatal(err)
-		}
-		format = f
-	}
-
-	enc, err := bkl.FormatOutput(out, format)
+	// Pass output path and input path - FormatOutput will use their extensions if format is empty
+	enc, err := bkl.FormatOutput(out, format, (*string)(opts.OutputPath), &preparedPaths[0])
 	if err != nil {
 		fatal(err)
 	}

parser.go

@@ -351,8 +351,20 @@ func getOSEnv() map[string]string {
 }
 
 // FormatOutput marshals the given data to the specified format.
+// If format is empty, it looks at the provided paths (as string pointers) and uses
+// the file extension of the first non-nil path as the format.
 // Returns the marshaled bytes or an error if the format is unknown or marshaling fails.
-func FormatOutput(data any, format string) ([]byte, error) {
+func FormatOutput(data any, format string, paths ...*string) ([]byte, error) {
+	// If format is empty, try to infer from paths
+	if format == "" {
+		for _, path := range paths {
+			if path != nil && *path != "" {
+				format = Ext(*path)
+				break
+			}
+		}
+	}
+
 	f, found := formatByExtension[format]
 	if !found {
 		return nil, fmt.Errorf("%s: %w", format, ErrUnknownFormat)