build method

@override Future build(BuildStep buildStep)

Generates the outputs for a given BuildStep.

Implementation

@override
Future build(BuildStep buildStep) async {
  var content = await buildStep.readAsString(buildStep.inputId);

  var matches = _regex.allMatches(content);
  var output = StringBuffer();
  var lastEnd = 0;

  for (var match in matches) {
    output.write(content.substring(lastEnd, match.start));
    var group = match.group(0)!;

    // Remove the braces.
    group = group.substring(2, group.length - 2).trim();

    // Get the command and value.
    var parts = group.split(' ');
    var command = parts.first;
    var value = parts.last;

    switch (command) {
      case 'version':
        var pubspecAssetId =
            AssetId(buildStep.inputId.package, 'pubspec.yaml');

        // Check if we can load the pubspec file.
        if (!await buildStep.canRead(pubspecAssetId)) {
          log.severe(
              'Cannot read pubspec.yaml! Make sure it is included as a source in your target.');
          return;
        }

        var pubspec = await buildStep.readAsString(pubspecAssetId);
        var pubspecYaml = loadYaml(pubspec);

        // Check if the yaml file have been parsed well.
        if (pubspecYaml == null) {
          log.severe(
              'Cannot read pubspec.yaml! Make sure it is included as a source in your target.');
          return;
        }

        // Check if the version is set.
        if (pubspecYaml['version'] == null) {
          log.severe('Cannot read version from pubspec.yaml!');
          return;
        }

        output.write(pubspecYaml['version']);
        break;

      case 'digest':
        if (value.isEmpty) {
          log.severe('''
Invalid template tag ${match.group(0)}.
Expected a command followed by a value, like {{command value}}.
''');
          return;
        }

        var id = AssetId.resolve(Uri.parse(value), from: buildStep.inputId);
        output.write(await buildStep.digest(id));
        break;
      default:
        log.severe('Unrecognized template command: $command');
    }

    lastEnd = match.end;
  }

  output.write(content.substring(lastEnd, content.length));

  await buildStep.writeAsString(
    buildStep.inputId
        .changeExtension('')
        .changeExtension(buildStep.inputId.extension),
    output.toString(),
  );
}