lottie-flutter/example/tool/generate_file_list.dart

import 'dart:io';
import 'package:path/path.dart' as p;

void main() {
  var buffer = StringBuffer();
  buffer.writeln('// Generated from tool/generate_file_list.dart');
  buffer.writeln('final files = [');

  var allFiles = Directory('assets')
      .listSync(recursive: true)
      .whereType<File>()
      .where((f) =>
          (f.path.endsWith('.json') || f.path.endsWith('.zip')) &&
          !p.basename(f.path).startsWith('_'))
      .toList();
  allFiles.sort((a, b) => a.path.compareTo(b.path));
  for (var file in allFiles) {
    buffer.writeln("  '${file.path}',");
  }
  buffer.writeln('];');
  File('lib/src/all_files.g.dart').writeAsStringSync('$buffer');
}