build.yaml

# Read about `build.yaml` at https://pub.dev/packages/build_config
targets:
  $default:
    builders:
      assets_scanner|assets_generator:
        enabled: true
        # Only run this builder on the specified input.
        # generate_for:
        #   include: ['**.assets.dart']

builders:
  # name of the builder
  assets_generator:
    # library URI containing the builder - maps to `lib/builder.dart`
    import: "package:assets_scanner/assets_scanner.dart"
    # Name of the function in the above library to call.
    builder_factories: ["assetScannerBuilder"]
    # The mapping from the source extension to the generated file extension
    build_extensions: {r'$lib$': ["r.dart"]}
    # Will automatically run on any package that depends on it
    auto_apply: dependents
    # Generate the output directly into the package, not to a hidden cache dir
    build_to: source
    # applies_builders: ["source_gen|combining_builder"]