lib/src/dartdevc/dartdevc.dart - pub - Git at Google

 // Copyright (c) 2017, 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 'dart:convert' show JsonEncoder;
 import 'dart:io';

 import 'package:analyzer/analyzer.dart';
 import 'package:barback/barback.dart';
 import 'package:bazel_worker/bazel_worker.dart';
 import 'package:cli_util/cli_util.dart' as cli_util;
 import 'package:path/path.dart' as p;

 import '../dart.dart';
 import '../io.dart';
 import 'errors.dart';
 import 'module_reader.dart';
 import 'scratch_space.dart';
 import 'summaries.dart';
 import 'workers.dart';

 /// JavaScript snippet to determine the directory a script was run from.
 final _currentDirectoryScript = r'''
 var _currentDirectory = (function () {
   var _url;
   var lines = new Error().stack.split('\n');
   function lookupUrl() {
     if (lines.length > 2) {
       var match = lines[1].match(/^\s+at (.+):\d+:\d+$/);
       // Chrome.
       if (match) return match[1];
       // Chrome nested eval case.
       match = lines[1].match(/^\s+at eval [(](.+):\d+:\d+[)]$/);
       if (match) return match[1];
       // Edge.
       match = lines[1].match(/^\s+at.+\((.+):\d+:\d+\)$/);
       if (match) return match[1];
       // Firefox.
       match = lines[0].match(/[<][@](.+):\d+:\d+$/)
       if (match) return match[1];
     }
     // Safari.
     return lines[0].match(/(.+):\d+:\d+$/)[1];
   }
   _url = lookupUrl();
   var lastSlash = _url.lastIndexOf('/');
   if (lastSlash == -1) return _url;
   var currentDirectory = _url.substring(0, lastSlash + 1);
   return currentDirectory;
 })();
 ''';

 /// Returns whether or not [dartId] is an app entrypoint (basically, whether or
 /// not it has a `main` function).
 Future<bool> isAppEntryPoint(
     AssetId dartId, Future<Asset> getAsset(AssetId id)) async {
   assert(dartId.extension == '.dart');
   var dartAsset = await getAsset(dartId);
   // Skip reporting errors here, dartdevc will report them later with nicer
   // formatting.
   var parsed = parseCompilationUnit(await dartAsset.readAsString(),
       suppressErrors: true);
   return isEntrypoint(parsed);
 }

 /// Bootstraps the JS module for the entrypoint dart file [dartEntrypointId]
 /// with two additional JS files:
 ///
 /// * A `$dartEntrypointId.js` file which is the main entrypoint for the app. It
 ///   injects a script tag whose src is `require.js` and whose `data-main`
 ///   attribute points at a `$dartEntrypointId.bootstrap.js` file.
 /// * A `$dartEntrypointId.bootstrap.js` file which invokes the top level `main`
 ///   function from the entrypoint module, after performing some necessary SDK
 ///   setup.
 ///
 /// In debug mode an empty sourcemap will be output for the entrypoint JS file
 /// to satisfy the test package runner (there is no original dart file to map it
 /// back to though).
 ///
 /// Synchronously returns a `Map<AssetId, Future<Asset>>` so that you can know
 /// immediately what assets will be output.
 Map<AssetId, Future<Asset>> bootstrapDartDevcEntrypoint(
     AssetId dartEntrypointId, BarbackMode mode, ModuleReader moduleReader) {
   var bootstrapId = dartEntrypointId.addExtension('.bootstrap.js');
   var jsEntrypointId = dartEntrypointId.addExtension('.js');
   var jsMapEntrypointId = jsEntrypointId.addExtension('.map');

   var outputCompleters = <AssetId, Completer<Asset>>{
     bootstrapId: new Completer(),
     jsEntrypointId: new Completer(),
   };
   var isDebug = mode == BarbackMode.DEBUG;

   if (isDebug) {
     outputCompleters[jsMapEntrypointId] = new Completer<Asset>();
   }

   return _ensureComplete(outputCompleters, () async {
     var module = await moduleReader.moduleFor(dartEntrypointId);

     // The path to the entrypoint JS module as it should appear in the call to
     // `require` in the bootstrap file.
     var moduleDir = topLevelDir(dartEntrypointId.path);
     var appModulePath = p.url.relative(p.url.join(moduleDir, module.id.name),
         from: p.url.dirname(dartEntrypointId.path));

     // The name of the entrypoint dart library within the entrypoint JS module.
     //
     // This is used to invoke `main()` from within the bootstrap script.
     //
     // TODO(jakemac53): Sane module name creation, this only works in the most
     // basic of cases.
     //
     // See https://github.com/dart-lang/sdk/issues/27262 for the root issue
     // which will allow us to not rely on the naming schemes that dartdevc uses
     // internally, but instead specify our own.
     var appModuleScope = p.url
         .split(p.url.withoutExtension(
             p.url.relative(dartEntrypointId.path, from: moduleDir)))
         .join("__")
         .replaceAll('.', '\$46');

     // Map from module name to module path.
     // Modules outside of the `packages` directory have different module path
     // and module names.
     var modulePaths = {appModulePath: appModulePath, 'dart_sdk': 'dart_sdk'};
     var transitiveDeps = await moduleReader.readTransitiveDeps(module);
     for (var dep in transitiveDeps) {
       if (dep.dir != 'lib') {
         var relativePath = p.url.relative(p.url.join(moduleDir, dep.name),
             from: p.url.dirname(bootstrapId.path));
         var jsModuleName = '${dep.dir}/${dep.name}';

         modulePaths[jsModuleName] = relativePath;
       } else {
         var jsModuleName = 'packages/${dep.package}/${dep.name}';
         var actualModulePath = p.url.relative(
             p.url.join(moduleDir, jsModuleName),
             from: p.url.dirname(bootstrapId.path));
         modulePaths[jsModuleName] = actualModulePath;
       }
     }
     var bootstrapContent = new StringBuffer('(function() {\n');
     if (isDebug) {
       bootstrapContent.write('''
 $_currentDirectoryScript
 let modulePaths = ${const JsonEncoder.withIndent(" ").convert(modulePaths)};

 if(!window.\$dartLoader) {
    window.\$dartLoader = {
      moduleIdToUrl: new Map(),
      urlToModuleId: new Map(),
      rootDirectories: new Set(),
    };
 }

 let customModulePaths = {};
 window.\$dartLoader.rootDirectories.add(_currentDirectory);
 for (let moduleName of Object.getOwnPropertyNames(modulePaths)) {
   let modulePath = modulePaths[moduleName];
   if (modulePath != moduleName) {
     customModulePaths[moduleName] = modulePath;
   }
   var src = _currentDirectory + modulePath + '.js';
   if (window.\$dartLoader.moduleIdToUrl.has(moduleName)) {
     continue;
   }
   \$dartLoader.moduleIdToUrl.set(moduleName, src);
   \$dartLoader.urlToModuleId.set(src, moduleName);
 }
 ''');
     } else {
       var customModulePaths = <String, String>{};
       modulePaths.forEach((name, path) {
         if (name != path) customModulePaths[name] = path;
       });
       var json = const JsonEncoder.withIndent(" ").convert(customModulePaths);
       bootstrapContent.write('let customModulePaths = ${json};\n');
     }

     bootstrapContent.write('''
 // Whenever we fail to load a JS module, try to request the corresponding
 // `.errors` file, and log it to the console.
 (function() {
   var oldOnError = requirejs.onError;
   requirejs.onError = function(e) {
     if (e.originalError && e.originalError.srcElement) {
       var xhr = new XMLHttpRequest();
       xhr.onreadystatechange = function() {
         if (this.readyState == 4 && this.status == 200) {
           console.error(this.responseText);
         }
       };
       xhr.open("GET", e.originalError.srcElement.src + ".errors", true);
       xhr.send();
     }
     // Also handle errors the normal way.
     if (oldOnError) oldOnError(e);
   };
 }());

 require.config({
     waitSeconds: 30,
     paths: customModulePaths
 });

 require(["$appModulePath", "dart_sdk"], function(app, dart_sdk) {
   dart_sdk._isolate_helper.startRootIsolate(() => {}, []);
 ''');

     if (isDebug) {
       bootstrapContent.write('''
   dart_sdk._debugger.registerDevtoolsFormatter();

   if (window.\$dartStackTraceUtility && !window.\$dartStackTraceUtility.ready) {
     window.\$dartStackTraceUtility.ready = true;
     let dart = dart_sdk.dart;
     window.\$dartStackTraceUtility.setSourceMapProvider(
       function(url) {
         var module = window.\$dartLoader.urlToModuleId.get(url);
         if (!module) return null;
         return dart.getSourceMap(module);
       });
   }
   window.postMessage({ type: "DDC_STATE_CHANGE", state: "start" }, "*");
 ''');
     }

     bootstrapContent.write('''
   app.$appModuleScope.main();
 });
 })();
 ''');
     outputCompleters[bootstrapId].complete(
         new Asset.fromString(bootstrapId, bootstrapContent.toString()));

     var bootstrapModuleName = p.withoutExtension(
         p.relative(bootstrapId.path, from: p.dirname(dartEntrypointId.path)));
     var entrypointJsContent = new StringBuffer('''
 var el;
 ''');
     if (isDebug) {
       entrypointJsContent.write('''
 el = document.createElement("script");
 el.defer = true;
 el.async = false;
 el.src = "dart_stack_trace_mapper.js";
 document.head.appendChild(el);
 ''');
     }

     entrypointJsContent.write('''
 el = document.createElement("script");
 el.defer = true;
 el.async = false;
 el.src = "require.js";
 el.setAttribute("data-main", "$bootstrapModuleName");
 document.head.appendChild(el);
 ''');
     outputCompleters[jsEntrypointId].complete(
         new Asset.fromString(jsEntrypointId, entrypointJsContent.toString()));

     if (isDebug) {
       outputCompleters[jsMapEntrypointId].complete(new Asset.fromString(
           jsMapEntrypointId,
           '{"version":3,"sourceRoot":"","sources":[],"names":[],"mappings":"",'
           '"file":""}'));
     }
   });
 }

 /// Compiles [module] using the `dartdevc` binary from the SDK to a relative
 /// path under the package that looks like `$outputDir/${module.id.name}.js`.
 ///
 /// Synchronously returns a `Map<AssetId, Future<Asset>>` so that you can know
 /// immediately what assets will be output.
 Map<AssetId, Future<Asset>> createDartdevcModule(
     AssetId id,
     ModuleReader moduleReader,
     ScratchSpace scratchSpace,
     Map<String, String> environmentConstants,
     BarbackMode mode) {
   assert(id.extension == '.js');
   var outputCompleters = <AssetId, Completer<Asset>>{
     id: new Completer(),
   };
   var isDebug = mode == BarbackMode.DEBUG;
   if (isDebug) {
     outputCompleters[id.addExtension('.map')] = new Completer();
   }

   return _ensureComplete(outputCompleters, () async {
     var module = await moduleReader.moduleFor(id);
     var transitiveModuleDeps = await moduleReader.readTransitiveDeps(module);
     var linkedSummaryIds =
         transitiveModuleDeps.map((depId) => depId.linkedSummaryId).toSet();
     var allAssetIds = new Set<AssetId>()
       ..addAll(module.assetIds)
       ..addAll(linkedSummaryIds);
     await scratchSpace.ensureAssets(allAssetIds);
     var jsOutputFile = scratchSpace.fileFor(module.id.jsId);
     var sdk_summary = p.url.join(sdkDir.path, 'lib/_internal/ddc_sdk.sum');
     var request = new WorkRequest();
     request.arguments.addAll([
       '--dart-sdk-summary=$sdk_summary',
       '--modules=amd',
       '--dart-sdk=${sdkDir.path}',
       '--module-root=${scratchSpace.tempDir.path}',
       '--library-root=${p.dirname(jsOutputFile.path)}',
       '--summary-extension=${linkedSummaryExtension.substring(1)}',
       '--no-summarize',
       '-o',
       jsOutputFile.path,
     ]);

     if (isDebug) {
       request.arguments.addAll([
         '--source-map',
         '--source-map-comment',
         '--inline-source-map',
       ]);
     } else {
       request.arguments.add('--no-source-map');
     }

     // Add environment constants.
     environmentConstants.forEach((key, value) {
       request.arguments.add('-D$key=$value');
     });

     // Add all the linked summaries as summary inputs.
     for (var id in linkedSummaryIds) {
       request.arguments.addAll(['-s', scratchSpace.fileFor(id).path]);
     }

     // Add URL mappings for all the package: files to tell DartDevc where to
     // find them.
     for (var id in module.assetIds) {
       var uri = canonicalUriFor(id);
       if (uri.startsWith('package:')) {
         request.arguments
             .add('--url-mapping=$uri,${scratchSpace.fileFor(id).path}');
       }
     }
     // And finally add all the urls to compile, using the package: path for
     // files under lib and the full absolute path for other files.
     request.arguments.addAll(module.assetIds.map((id) {
       var uri = canonicalUriFor(id);
       if (uri.startsWith('package:')) {
         return uri;
       }
       return scratchSpace.fileFor(id).path;
     }));

     var response = await dartdevcDriver.doWork(request);

     // TODO(jakemac53): Fix the ddc worker mode so it always sends back a bad
     // status code if something failed. Today we just make sure there is an output
     // JS file to verify it was successful.
     if (response.exitCode != EXIT_CODE_OK || !jsOutputFile.existsSync()) {
       outputCompleters[module.id.jsId].completeError(
           new DartDevcCompilationException(module.id.jsId, response.output));
     } else {
       outputCompleters[module.id.jsId].complete(
           new Asset.fromBytes(module.id.jsId, jsOutputFile.readAsBytesSync()));
       if (isDebug) {
         var sourceMapFile = scratchSpace.fileFor(module.id.jsSourceMapId);
         outputCompleters[module.id.jsSourceMapId].complete(new Asset.fromBytes(
             module.id.jsSourceMapId, sourceMapFile.readAsBytesSync()));
       }
     }
   });
 }

 /// Copies the `dart_sdk.js` and `require.js` AMD files from the SDK into
 /// [outputDir].
 ///
 /// Returns a `Map<AssetId, Asset>` of the created assets.
 Map<AssetId, Asset> copyDartDevcResources(String package, String outputDir) {
   var sdk = cli_util.getSdkDir();
   var outputs = <AssetId, Asset>{};

   // Copy the dart_sdk.js file for AMD into the output folder.
   var sdkJsOutputId =
       new AssetId(package, p.url.join(outputDir, 'dart_sdk.js'));
   var sdkAmdJsPath = p.url.join(sdk.path, 'lib/dev_compiler/amd/dart_sdk.js');
   outputs[sdkJsOutputId] =
       new Asset.fromFile(sdkJsOutputId, new File(sdkAmdJsPath));

   // Copy the require.js file for AMD into the output folder.
   var requireJsPath = p.url.join(sdk.path, 'lib/dev_compiler/amd/require.js');
   var requireJsOutputId =
       new AssetId(package, p.url.join(outputDir, 'require.js'));
   outputs[requireJsOutputId] =
       new Asset.fromFile(requireJsOutputId, new File(requireJsPath));

   return outputs;
 }

 /// Runs [fn], and then ensures that all [completers] are completed.
 ///
 /// If an error is caught, then all [completers] that weren't completed are
 /// completed with that error and stack trace.
 ///
 /// If no error was caught then all [completers] that weren't completed are
 /// completed with an [AssetNotFoundException].
 ///
 /// Synchronously returns a `Map<AssetId, Future<Asset>` which is derived from
 /// the original [completers].
 Map<AssetId, Future<Asset>> _ensureComplete(
     Map<AssetId, Completer<Asset>> completers, Future fn()) {
   var futures = <AssetId, Future<Asset>>{};
   completers.forEach((k, v) => futures[k] = v.future);
   () async {
     try {
       await fn();
     } catch (e, s) {
       for (var completer in completers.values) {
         if (!completer.isCompleted) completer.completeError(e, s);
       }
     } finally {
       for (var id in completers.keys) {
         if (!completers[id].isCompleted) {
           completers[id].completeError(new AssetNotFoundException(id));
         }
       }
     }
   }();
   return futures;
 }
	// Copyright (c) 2017, 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 'dart:convert' show JsonEncoder;
	import 'dart:io';

	import 'package:analyzer/analyzer.dart';
	import 'package:barback/barback.dart';
	import 'package:bazel_worker/bazel_worker.dart';
	import 'package:cli_util/cli_util.dart' as cli_util;
	import 'package:path/path.dart' as p;

	import '../dart.dart';
	import '../io.dart';
	import 'errors.dart';
	import 'module_reader.dart';
	import 'scratch_space.dart';
	import 'summaries.dart';
	import 'workers.dart';

	/// JavaScript snippet to determine the directory a script was run from.
	final _currentDirectoryScript = r'''
	var _currentDirectory = (function () {
	var _url;
	var lines = new Error().stack.split('\n');
	function lookupUrl() {
	if (lines.length > 2) {
	var match = lines[1].match(/^\s+at (.+):\d+:\d+$/);
	// Chrome.
	if (match) return match[1];
	// Chrome nested eval case.
	match = lines[1].match(/^\s+at eval [(](.+):\d+:\d+[)]$/);
	if (match) return match[1];
	// Edge.
	match = lines[1].match(/^\s+at.+\((.+):\d+:\d+\)$/);
	if (match) return match[1];
	// Firefox.
	match = lines[0].match(/[<][@](.+):\d+:\d+$/)
	if (match) return match[1];
	}
	// Safari.
	return lines[0].match(/(.+):\d+:\d+$/)[1];
	}
	_url = lookupUrl();
	var lastSlash = _url.lastIndexOf('/');
	if (lastSlash == -1) return _url;
	var currentDirectory = _url.substring(0, lastSlash + 1);
	return currentDirectory;
	})();
	''';

	/// Returns whether or not [dartId] is an app entrypoint (basically, whether or
	/// not it has a `main` function).
	Future<bool> isAppEntryPoint(
	AssetId dartId, Future<Asset> getAsset(AssetId id)) async {
	assert(dartId.extension == '.dart');
	var dartAsset = await getAsset(dartId);
	// Skip reporting errors here, dartdevc will report them later with nicer
	// formatting.
	var parsed = parseCompilationUnit(await dartAsset.readAsString(),
	suppressErrors: true);
	return isEntrypoint(parsed);
	}

	/// Bootstraps the JS module for the entrypoint dart file [dartEntrypointId]
	/// with two additional JS files:
	///
	/// * A `$dartEntrypointId.js` file which is the main entrypoint for the app. It
	/// injects a script tag whose src is `require.js` and whose `data-main`
	/// attribute points at a `$dartEntrypointId.bootstrap.js` file.
	/// * A `$dartEntrypointId.bootstrap.js` file which invokes the top level `main`
	/// function from the entrypoint module, after performing some necessary SDK
	/// setup.
	///
	/// In debug mode an empty sourcemap will be output for the entrypoint JS file
	/// to satisfy the test package runner (there is no original dart file to map it
	/// back to though).
	///
	/// Synchronously returns a `Map<AssetId, Future<Asset>>` so that you can know
	/// immediately what assets will be output.
	Map<AssetId, Future<Asset>> bootstrapDartDevcEntrypoint(
	AssetId dartEntrypointId, BarbackMode mode, ModuleReader moduleReader) {
	var bootstrapId = dartEntrypointId.addExtension('.bootstrap.js');
	var jsEntrypointId = dartEntrypointId.addExtension('.js');
	var jsMapEntrypointId = jsEntrypointId.addExtension('.map');

	var outputCompleters = <AssetId, Completer<Asset>>{
	bootstrapId: new Completer(),
	jsEntrypointId: new Completer(),
	};
	var isDebug = mode == BarbackMode.DEBUG;

	if (isDebug) {
	outputCompleters[jsMapEntrypointId] = new Completer<Asset>();
	}

	return _ensureComplete(outputCompleters, () async {
	var module = await moduleReader.moduleFor(dartEntrypointId);

	// The path to the entrypoint JS module as it should appear in the call to
	// `require` in the bootstrap file.
	var moduleDir = topLevelDir(dartEntrypointId.path);
	var appModulePath = p.url.relative(p.url.join(moduleDir, module.id.name),
	from: p.url.dirname(dartEntrypointId.path));

	// The name of the entrypoint dart library within the entrypoint JS module.
	//
	// This is used to invoke `main()` from within the bootstrap script.
	//
	// TODO(jakemac53): Sane module name creation, this only works in the most
	// basic of cases.
	//
	// See https://github.com/dart-lang/sdk/issues/27262 for the root issue
	// which will allow us to not rely on the naming schemes that dartdevc uses
	// internally, but instead specify our own.
	var appModuleScope = p.url
	.split(p.url.withoutExtension(
	p.url.relative(dartEntrypointId.path, from: moduleDir)))
	.join("__")
	.replaceAll('.', '\$46');

	// Map from module name to module path.
	// Modules outside of the `packages` directory have different module path
	// and module names.
	var modulePaths = {appModulePath: appModulePath, 'dart_sdk': 'dart_sdk'};
	var transitiveDeps = await moduleReader.readTransitiveDeps(module);
	for (var dep in transitiveDeps) {
	if (dep.dir != 'lib') {
	var relativePath = p.url.relative(p.url.join(moduleDir, dep.name),
	from: p.url.dirname(bootstrapId.path));
	var jsModuleName = '${dep.dir}/${dep.name}';

	modulePaths[jsModuleName] = relativePath;
	} else {
	var jsModuleName = 'packages/${dep.package}/${dep.name}';
	var actualModulePath = p.url.relative(
	p.url.join(moduleDir, jsModuleName),
	from: p.url.dirname(bootstrapId.path));
	modulePaths[jsModuleName] = actualModulePath;
	}
	}
	var bootstrapContent = new StringBuffer('(function() {\n');
	if (isDebug) {
	bootstrapContent.write('''
	$_currentDirectoryScript
	let modulePaths = ${const JsonEncoder.withIndent(" ").convert(modulePaths)};

	if(!window.\$dartLoader) {
	window.\$dartLoader = {
	moduleIdToUrl: new Map(),
	urlToModuleId: new Map(),
	rootDirectories: new Set(),
	};
	}

	let customModulePaths = {};
	window.\$dartLoader.rootDirectories.add(_currentDirectory);
	for (let moduleName of Object.getOwnPropertyNames(modulePaths)) {
	let modulePath = modulePaths[moduleName];
	if (modulePath != moduleName) {
	customModulePaths[moduleName] = modulePath;
	}
	var src = _currentDirectory + modulePath + '.js';
	if (window.\$dartLoader.moduleIdToUrl.has(moduleName)) {
	continue;
	}
	\$dartLoader.moduleIdToUrl.set(moduleName, src);
	\$dartLoader.urlToModuleId.set(src, moduleName);
	}
	''');
	} else {
	var customModulePaths = <String, String>{};
	modulePaths.forEach((name, path) {
	if (name != path) customModulePaths[name] = path;
	});
	var json = const JsonEncoder.withIndent(" ").convert(customModulePaths);
	bootstrapContent.write('let customModulePaths = ${json};\n');
	}

	bootstrapContent.write('''
	// Whenever we fail to load a JS module, try to request the corresponding
	// `.errors` file, and log it to the console.
	(function() {
	var oldOnError = requirejs.onError;
	requirejs.onError = function(e) {
	if (e.originalError && e.originalError.srcElement) {
	var xhr = new XMLHttpRequest();
	xhr.onreadystatechange = function() {
	if (this.readyState == 4 && this.status == 200) {
	console.error(this.responseText);
	}
	};
	xhr.open("GET", e.originalError.srcElement.src + ".errors", true);
	xhr.send();
	}
	// Also handle errors the normal way.
	if (oldOnError) oldOnError(e);
	};
	}());

	require.config({
	waitSeconds: 30,
	paths: customModulePaths
	});

	require(["$appModulePath", "dart_sdk"], function(app, dart_sdk) {
	dart_sdk._isolate_helper.startRootIsolate(() => {}, []);
	''');

	if (isDebug) {
	bootstrapContent.write('''
	dart_sdk._debugger.registerDevtoolsFormatter();

	if (window.\$dartStackTraceUtility && !window.\$dartStackTraceUtility.ready) {
	window.\$dartStackTraceUtility.ready = true;
	let dart = dart_sdk.dart;
	window.\$dartStackTraceUtility.setSourceMapProvider(
	function(url) {
	var module = window.\$dartLoader.urlToModuleId.get(url);
	if (!module) return null;
	return dart.getSourceMap(module);
	});
	}
	window.postMessage({ type: "DDC_STATE_CHANGE", state: "start" }, "*");
	''');
	}

	bootstrapContent.write('''
	app.$appModuleScope.main();
	});
	})();
	''');
	outputCompleters[bootstrapId].complete(
	new Asset.fromString(bootstrapId, bootstrapContent.toString()));

	var bootstrapModuleName = p.withoutExtension(
	p.relative(bootstrapId.path, from: p.dirname(dartEntrypointId.path)));
	var entrypointJsContent = new StringBuffer('''
	var el;
	''');
	if (isDebug) {
	entrypointJsContent.write('''
	el = document.createElement("script");
	el.defer = true;
	el.async = false;
	el.src = "dart_stack_trace_mapper.js";
	document.head.appendChild(el);
	''');
	}

	entrypointJsContent.write('''
	el = document.createElement("script");
	el.defer = true;
	el.async = false;
	el.src = "require.js";
	el.setAttribute("data-main", "$bootstrapModuleName");
	document.head.appendChild(el);
	''');
	outputCompleters[jsEntrypointId].complete(
	new Asset.fromString(jsEntrypointId, entrypointJsContent.toString()));

	if (isDebug) {
	outputCompleters[jsMapEntrypointId].complete(new Asset.fromString(
	jsMapEntrypointId,
	'{"version":3,"sourceRoot":"","sources":[],"names":[],"mappings":"",'
	'"file":""}'));
	}
	});
	}

	/// Compiles [module] using the `dartdevc` binary from the SDK to a relative
	/// path under the package that looks like `$outputDir/${module.id.name}.js`.
	///
	/// Synchronously returns a `Map<AssetId, Future<Asset>>` so that you can know
	/// immediately what assets will be output.
	Map<AssetId, Future<Asset>> createDartdevcModule(
	AssetId id,
	ModuleReader moduleReader,
	ScratchSpace scratchSpace,
	Map<String, String> environmentConstants,
	BarbackMode mode) {
	assert(id.extension == '.js');
	var outputCompleters = <AssetId, Completer<Asset>>{
	id: new Completer(),
	};
	var isDebug = mode == BarbackMode.DEBUG;
	if (isDebug) {
	outputCompleters[id.addExtension('.map')] = new Completer();
	}

	return _ensureComplete(outputCompleters, () async {
	var module = await moduleReader.moduleFor(id);
	var transitiveModuleDeps = await moduleReader.readTransitiveDeps(module);
	var linkedSummaryIds =
	transitiveModuleDeps.map((depId) => depId.linkedSummaryId).toSet();
	var allAssetIds = new Set<AssetId>()
	..addAll(module.assetIds)
	..addAll(linkedSummaryIds);
	await scratchSpace.ensureAssets(allAssetIds);
	var jsOutputFile = scratchSpace.fileFor(module.id.jsId);
	var sdk_summary = p.url.join(sdkDir.path, 'lib/_internal/ddc_sdk.sum');
	var request = new WorkRequest();
	request.arguments.addAll([
	'--dart-sdk-summary=$sdk_summary',
	'--modules=amd',
	'--dart-sdk=${sdkDir.path}',
	'--module-root=${scratchSpace.tempDir.path}',
	'--library-root=${p.dirname(jsOutputFile.path)}',
	'--summary-extension=${linkedSummaryExtension.substring(1)}',
	'--no-summarize',
	'-o',
	jsOutputFile.path,
	]);

	if (isDebug) {
	request.arguments.addAll([
	'--source-map',
	'--source-map-comment',
	'--inline-source-map',
	]);
	} else {
	request.arguments.add('--no-source-map');
	}

	// Add environment constants.
	environmentConstants.forEach((key, value) {
	request.arguments.add('-D$key=$value');
	});

	// Add all the linked summaries as summary inputs.
	for (var id in linkedSummaryIds) {
	request.arguments.addAll(['-s', scratchSpace.fileFor(id).path]);
	}

	// Add URL mappings for all the package: files to tell DartDevc where to
	// find them.
	for (var id in module.assetIds) {
	var uri = canonicalUriFor(id);
	if (uri.startsWith('package:')) {
	request.arguments
	.add('--url-mapping=$uri,${scratchSpace.fileFor(id).path}');
	}
	}
	// And finally add all the urls to compile, using the package: path for
	// files under lib and the full absolute path for other files.
	request.arguments.addAll(module.assetIds.map((id) {
	var uri = canonicalUriFor(id);
	if (uri.startsWith('package:')) {
	return uri;
	}
	return scratchSpace.fileFor(id).path;
	}));

	var response = await dartdevcDriver.doWork(request);

	// TODO(jakemac53): Fix the ddc worker mode so it always sends back a bad
	// status code if something failed. Today we just make sure there is an output
	// JS file to verify it was successful.
	if (response.exitCode != EXIT_CODE_OK \|\| !jsOutputFile.existsSync()) {
	outputCompleters[module.id.jsId].completeError(
	new DartDevcCompilationException(module.id.jsId, response.output));
	} else {
	outputCompleters[module.id.jsId].complete(
	new Asset.fromBytes(module.id.jsId, jsOutputFile.readAsBytesSync()));
	if (isDebug) {
	var sourceMapFile = scratchSpace.fileFor(module.id.jsSourceMapId);
	outputCompleters[module.id.jsSourceMapId].complete(new Asset.fromBytes(
	module.id.jsSourceMapId, sourceMapFile.readAsBytesSync()));
	}
	}
	});
	}

	/// Copies the `dart_sdk.js` and `require.js` AMD files from the SDK into
	/// [outputDir].
	///
	/// Returns a `Map<AssetId, Asset>` of the created assets.
	Map<AssetId, Asset> copyDartDevcResources(String package, String outputDir) {
	var sdk = cli_util.getSdkDir();
	var outputs = <AssetId, Asset>{};

	// Copy the dart_sdk.js file for AMD into the output folder.
	var sdkJsOutputId =
	new AssetId(package, p.url.join(outputDir, 'dart_sdk.js'));
	var sdkAmdJsPath = p.url.join(sdk.path, 'lib/dev_compiler/amd/dart_sdk.js');
	outputs[sdkJsOutputId] =
	new Asset.fromFile(sdkJsOutputId, new File(sdkAmdJsPath));

	// Copy the require.js file for AMD into the output folder.
	var requireJsPath = p.url.join(sdk.path, 'lib/dev_compiler/amd/require.js');
	var requireJsOutputId =
	new AssetId(package, p.url.join(outputDir, 'require.js'));
	outputs[requireJsOutputId] =
	new Asset.fromFile(requireJsOutputId, new File(requireJsPath));

	return outputs;
	}

	/// Runs [fn], and then ensures that all [completers] are completed.
	///
	/// If an error is caught, then all [completers] that weren't completed are
	/// completed with that error and stack trace.
	///
	/// If no error was caught then all [completers] that weren't completed are
	/// completed with an [AssetNotFoundException].
	///
	/// Synchronously returns a `Map<AssetId, Future<Asset>` which is derived from
	/// the original [completers].
	Map<AssetId, Future<Asset>> _ensureComplete(
	Map<AssetId, Completer<Asset>> completers, Future fn()) {
	var futures = <AssetId, Future<Asset>>{};
	completers.forEach((k, v) => futures[k] = v.future);
	() async {
	try {
	await fn();
	} catch (e, s) {
	for (var completer in completers.values) {
	if (!completer.isCompleted) completer.completeError(e, s);
	}
	} finally {
	for (var id in completers.keys) {
	if (!completers[id].isCompleted) {
	completers[id].completeError(new AssetNotFoundException(id));
	}
	}
	}
	}();
	return futures;
	}