Introduces the new syntax for deferred loading

sdk/lib/_internal/lib/async_patch.dart

 // Copyright (c) 2012, 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.
 
 // Patch file for the dart:async library.
 
-import 'dart:_js_helper' show Primitives, convertDartClosureToJS;
-import 'dart:_isolate_helper' show
-    IsolateNatives,
-    TimerImpl,
-    leaveJsAsync,
-    enterJsAsync,
-    isWorker;
+import 'dart:_js_helper' show
+    Primitives,
+    convertDartClosureToJS,
+    loadDeferredLibrary;
+import 'dart:_isolate_helper' show TimerImpl;
 
 import 'dart:_foreign_helper' show JS;
 
 patch Timer _createTimer(Duration duration, void callback()) {
   int milliseconds = duration.inMilliseconds;
   if (milliseconds < 0) milliseconds = 0;
   return new TimerImpl(milliseconds, callback);
 }
 
 patch Timer _createPeriodicTimer(Duration duration,
                                  void callback(Timer timer)) {
   int milliseconds = duration.inMilliseconds;
   if (milliseconds < 0) milliseconds = 0;
   return new TimerImpl.periodic(milliseconds, callback);
 }
 
 patch class _AsyncRun {
   patch static void _scheduleImmediate(void callback()) {
     // TODO(9002): don't use the Timer to enqueue the immediate callback.
     _createTimer(Duration.ZERO, callback);
   }
 }
 
 patch class DeferredLibrary {
   patch Future<bool> load() {
-    List hunkNames = new List();
-    if (JS('bool', '\$.libraries_to_load[#] === undefined', libraryName)) {
-      return new Future(() => false);
-    }
-    for (int index = 0;
-         index < JS('int', '\$.libraries_to_load[#].length', libraryName);
-         ++index) {
-      hunkNames.add(JS('String', '\$.libraries_to_load[#][#]',
-                       libraryName, index));
-    }
-    Iterable<Future<bool>> allLoads =
-        hunkNames.map((hunkName) => _load(hunkName, uri));
-    return Future.wait(allLoads).then((results) {
-      return results.any((x) => x);
-    });
+    return loadDeferredLibrary(libraryName, uri);
   }
 }
 
-// TODO(ahe): This should not only apply to this isolate.
-final Map<String, Future<bool>> _loadedLibraries = <String, Future<bool>>{};
-
-Future<bool> _load(String hunkName, String uri) {
-  // TODO(ahe): Validate libraryName.  Kasper points out that you want
-  // to be able to experiment with the effect of toggling @DeferLoad,
-  // so perhaps we should silently ignore "bad" library names.
-  Future<bool> future = _loadedLibraries[hunkName];
-  if (future != null) {
-    return future.then((_) => false);
-  }
-
-  if (uri == null) {
-    uri = IsolateNatives.thisScript;
-  }
-  int index = uri.lastIndexOf('/');
-  uri = '${uri.substring(0, index + 1)}$hunkName';
-
-  if (Primitives.isJsshell || Primitives.isD8) {
-    // TODO(ahe): Move this code to a JavaScript command helper script that is
-    // not included in generated output.
-    return _loadedLibraries[hunkName] = new Future<bool>(() {
-      try {
-        // Create a new function to avoid getting access to current function
-        // context.
-        JS('void', '(new Function(#))()', 'load("$uri")');
-      } catch (error, stackTrace) {
-        throw new DeferredLoadException("Loading $uri failed.");
-      }
-      return true;
-    });
-  } else if (isWorker()) {
-    // We are in a web worker. Load the code with an XMLHttpRequest.
-    return _loadedLibraries[hunkName] = new Future<bool>(() {
-      Completer completer = new Completer<bool>();
-      enterJsAsync();
-      Future<bool> leavingFuture = completer.future.whenComplete(() {
-        leaveJsAsync();
-      });
-
-      int index = uri.lastIndexOf('/');
-      uri = '${uri.substring(0, index + 1)}$hunkName';
-      var xhr =  JS('dynamic', 'new XMLHttpRequest()');
-      JS('void', '#.open("GET", #)', xhr, uri);
-      JS('void', '#.addEventListener("load", #, false)',
-         xhr, convertDartClosureToJS((event) {
-        if (JS('int', '#.status', xhr) != 200) {
-          completer.completeError(
-              new DeferredLoadException("Loading $uri failed."));
-          return;
-        }
-        String code = JS('String', '#.responseText', xhr);
-        try {
-          // Create a new function to avoid getting access to current function
-          // context.
-          JS('void', '(new Function(#))()', code);
-        } catch (error, stackTrace) {
-          completer.completeError(
-            new DeferredLoadException("Evaluating $uri failed."));
-          return;
-        }
-        completer.complete(true);
-      }, 1));
-
-      var fail = convertDartClosureToJS((event) {
-        new DeferredLoadException("Loading $uri failed.");
-      }, 1);
-      JS('void', '#.addEventListener("error", #, false)', xhr, fail);
-      JS('void', '#.addEventListener("abort", #, false)', xhr, fail);
-
-      JS('void', '#.send()', xhr);
-      return leavingFuture;
-    });
-  }
-  // We are in a dom-context.
-  return _loadedLibraries[hunkName] = new Future<bool>(() {
-    Completer completer = new Completer<bool>();
-    // Inject a script tag.
-    var script = JS('', 'document.createElement("script")');
-    JS('', '#.type = "text/javascript"', script);
-    JS('', '#.src = #', script, uri);
-    JS('', '#.addEventListener("load", #, false)',
-       script, convertDartClosureToJS((event) {
-      completer.complete(true);
-    }, 1));
-    JS('', '#.addEventListener("error", #, false)',
-       script, convertDartClosureToJS((event) {
-      completer.completeError(
-          new DeferredLoadException("Loading $uri failed."));
-    }, 1));
-    JS('', 'document.body.appendChild(#)', script);
-
-    return completer.future;
-  });
-}
-
 bool get _hasDocument => JS('String', 'typeof document') == 'object';