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// Copyright (c) 2015, 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.
import 'dart:async';
import 'package:barback/barback.dart';
import 'package:html5lib/dom.dart' as dom;
import 'package:html5lib/parser.dart';
import '../src/normalize_path.dart';
/// Given an html entry point with a single dart bootstrap file created by the
/// `initialize` transformer, this will open that dart file and remove all
/// `HtmlImport` initializers from it. Then it appends those imports to the head
/// of the html entry point.
/// Note: Does not inline the import, it just puts the <link rel="import"> tag.
class HtmlImportAnnotationInliner extends AggregateTransformer {
final String _bootstrapFile;
final String _htmlEntryPoint;
TransformLogger _logger;
HtmlImportAnnotationInliner(this._bootstrapFile, this._htmlEntryPoint);
factory HtmlImportAnnotationInliner.asPlugin(BarbackSettings settings) {
var bootstrapFile = settings.configuration['bootstrap_file'];
if (bootstrapFile is! String || !bootstrapFile.endsWith('.dart')) {
throw new ArgumentError(
'`bootstrap_file` should be a string path to a dart file');
var htmlEntryPoint = settings.configuration['html_entry_point'];
if (htmlEntryPoint is! String || !htmlEntryPoint.endsWith('.html')) {
throw new ArgumentError(
'`html_entry_point` should be a string path to an html file');
return new HtmlImportAnnotationInliner(bootstrapFile, htmlEntryPoint);
classifyPrimary(AssetId id) {
if (_bootstrapFile == id.path || _htmlEntryPoint == id.path) return ' ';
return null;
Future apply(AggregateTransform transform) {
_logger = transform.logger;
Asset dartEntryPoint;
Asset htmlEntryPoint;
return transform.primaryInputs.take(2).listen((Asset asset) {
if ( == _bootstrapFile) dartEntryPoint = asset;
if ( == _htmlEntryPoint) htmlEntryPoint = asset;
}).asFuture().then((_) {
// Will be populated with all import paths found in HtmlImport
// constructors.
var importPaths;
return dartEntryPoint.readAsString().then((dartCode) {
var matches = _htmlImportWithRawString.allMatches(dartCode);
importPaths = new Set.from( =>
normalizeHtmlImportPath(, == 'null' ? null :,;
var newDartCode = dartCode.replaceAll(_htmlImportWithRawString, '');
var leftoverMatches = _htmlImportGeneral.allMatches(newDartCode);
for (var match in leftoverMatches) {
_logger.warning('Found HtmlImport constructor which was supplied an '
'expression. Only raw strings are currently supported for the '
'transformer, so ${} will be injected dynamically');
new Asset.fromString(, newDartCode));
}).then((_) => htmlEntryPoint.readAsString()).then((html) {
var doc = parse(html);
for (var importPath in importPaths) {
var import = new dom.Element.tag('link')..attributes = {
'rel': 'import',
'href': importPath,
new Asset.fromString(, doc.outerHtml));
// Matches HtmlImport constructors which are supplied a raw string. These are
// the only ones currently supported for inlining.
final RegExp _htmlImportWithRawString = new RegExp(
r"\n\s*new InitEntry\(const i[\d]*\.HtmlImport\('([\w\d\/\.:]*\.html)'\),"
r"\sconst\sLibraryIdentifier\(#[\w\.]*, '?([\w_]*)'?, '([\w\d\/\.]*)'\)\)"
// Matches HtmlImport initializers which are supplied any arguments. This
// is used to detect if any were left over and not inlined.
final RegExp _htmlImportGeneral = new RegExp(
r"\n\s*new InitEntry\(const i[\d]*\.HtmlImport\(([\w\d\.]*)\),\s.*\),");