pkg/polymer/lib/src/build/build_filter.dart

// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/**
 * Final phase of the polymer transformation: removes any files that are not
 * needed for deployment.
 */
library polymer.src.build.build_filter;

import 'dart:async';

import 'package:barback/barback.dart';
import 'common.dart';

/**
 * Removes any files not needed for deployment, such as internal build artifacts
 * and non-entry HTML files.
 */
class BuildFilter extends Transformer with PolymerTransformer {
  final TransformOptions options;
  BuildFilter(this.options);

  Future<bool> isPrimary(Asset input) => new Future.value(
      // nothing is filtered in debug mode
      options.releaseMode &&
      // TODO(sigmund): remove this exclusion once we have dev_transformers
      // (dartbug.com/14187)
      input.id.path.startsWith('web/') &&
      // may filter non-entry HTML files and internal artifacts
      (input.id.extension == '.html' || input.id.extension == '.scriptUrls') &&
      // keep any entry points
      !options.isHtmlEntryPoint(input.id));

  Future apply(Transform transform) {
    if (transform.primaryInput.id.extension == '.scriptUrls') {
      return new Future.value(null);
    }
    return readPrimaryAsHtml(transform).then((document) {
      // Keep .html files that don't use polymer, since the app developer might
      // have non-polymer entrypoints.
      if (document.queryAll('polymer-element').isEmpty) {
        transform.addOutput(transform.primaryInput);
      }
    });
  }
}