prettyPrint function

String prettyPrint(Object? obj, { int indent = 0, })

Testing/Debug: pretty-print, dump iterable, assert equals with tolerance, range, repeat, timed. Roadmap #366-375. Recursively renders obj as an indented, human-readable string for debugging. Maps and lists are expanded over multiple lines; null becomes 'null' and any other value falls back to its toString(). indent sets the starting nesting depth (two spaces per level).

Example:

prettyPrint({'a': 1, 'b': [2, 3]});
// {
//   a: 1
//   b: [
//     2,
//     3
//   ]
// }

Implementation

/// Recursively renders [obj] as an indented, human-readable string for
/// debugging. Maps and lists are expanded over multiple lines; `null` becomes
/// `'null'` and any other value falls back to its `toString()`. [indent] sets
/// the starting nesting depth (two spaces per level).
///
/// Example:
/// ```dart
/// prettyPrint({'a': 1, 'b': [2, 3]});
/// // {
/// //   a: 1
/// //   b: [
/// //     2,
/// //     3
/// //   ]
/// // }
/// ```
String prettyPrint(Object? obj, {int indent = 0}) {
  const int spaces = 2;
  final String pad = ' ' * (indent * spaces);
  if (obj == null) return 'null';
  if (obj is Map) {
    if (obj.isEmpty) return '{}';
    final List<String> parts = <String>[];
    for (final MapEntry<dynamic, dynamic> e in obj.entries) {
      parts.add('$pad${e.key}: ${prettyPrint(e.value, indent: indent + 1)}');
    }
    return '{\n${parts.join('\n')}\n$pad}';
  }
  if (obj is List) {
    if (obj.isEmpty) return '[]';
    final List<String> parts = obj.map((Object? e) => prettyPrint(e, indent: indent + 1)).toList();
    return '[\n$pad${parts.join(',\n$pad')}\n$pad]';
  }
  return obj.toString();
}