First pass at asynchronous input loading in dart2js.

sdk/lib/_internal/compiler/implementation/patch_parser.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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 96 matching lines @@
  *   TODO(johnniwinther): Simplify this invariant to use only declarations in
  *   [tree.TreeElements].
  * - Builders shift between declaration and implementation depending on usages.
  * - Compile-time constants use constructor implementation exclusively.
  * - Work on function parameters is performed on the declaration of the function
  *   element.
  */
 
 library patchparser;
 
+import 'dart:async';
+
 import "tree/tree.dart" as tree;
 import "dart2jslib.dart" as leg;  // CompilerTask, Compiler.
 import "../compiler.dart" as api;
 import "scanner/scannerlib.dart";  // Scanner, Parsers, Listeners
 import "elements/elements.dart";
 import "elements/modelx.dart" show LibraryElementX, MetadataAnnotationX;
 import 'util/util.dart';
 
 class PatchParserTask extends leg.CompilerTask {
   PatchParserTask(leg.Compiler compiler): super(compiler);
   final String name = "Patching Parser";
 
   /**
    * Scans a library patch file, applies the method patches and
    * injections to the library, and returns a list of class
    * patches.
    */
-  void patchLibrary(leg.LibraryDependencyHandler handler,
+  Future patchLibrary(leg.LibraryDependencyHandler handler,
                     Uri patchUri, LibraryElement originLibrary) {
-
-    leg.Script script = compiler.readScript(patchUri, null);
-    var patchLibrary = new LibraryElementX(script, null, originLibrary);
-    compiler.withCurrentElement(patchLibrary, () {
-      handler.registerNewLibrary(patchLibrary);
-      LinkBuilder<tree.LibraryTag> imports = new LinkBuilder<tree.LibraryTag>();
-      compiler.withCurrentElement(patchLibrary.entryCompilationUnit, () {
-        // This patches the elements of the patch library into [library].
-        // Injected elements are added directly under the compilation unit.
-        // Patch elements are stored on the patched functions or classes.
-        scanLibraryElements(patchLibrary.entryCompilationUnit, imports);
+    return compiler.readScript(patchUri, null).then((leg.Script script) {
+      var patchLibrary = new LibraryElementX(script, null, originLibrary);
+      return compiler.withCurrentElement(patchLibrary, () {
+        handler.registerNewLibrary(patchLibrary);
+        var imports = new LinkBuilder<tree.LibraryTag>();
+        compiler.withCurrentElement(patchLibrary.entryCompilationUnit, () {
+          // This patches the elements of the patch library into [library].
+          // Injected elements are added directly under the compilation unit.
+          // Patch elements are stored on the patched functions or classes.
+          scanLibraryElements(patchLibrary.entryCompilationUnit, imports);
+        });
+        // After scanning declarations, we handle the import tags in the patch.
+        // TODO(lrn): These imports end up in the original library and are in
+        // scope for the original methods too. This should be fixed.
+        compiler.importHelperLibrary(originLibrary);
+        // TODO(rnystrom): Remove .toList() here if #11523 is fixed.
+        return Future.forEach(imports.toLink().toList(), (tag) {
+          return compiler.withCurrentElement(patchLibrary, () {
+            return compiler.libraryLoader.registerLibraryFromTag(
+                handler, patchLibrary, tag);
+          });
+        });
       });
-      // After scanning declarations, we handle the import tags in the patch.
-      // TODO(lrn): These imports end up in the original library and are in
-      // scope for the original methods too. This should be fixed.
-      compiler.importHelperLibrary(originLibrary);
-      for (tree.LibraryTag tag in imports.toLink()) {
-        compiler.libraryLoader.registerLibraryFromTag(
-            handler, patchLibrary, tag);
-      }
     });
   }
 
   void scanLibraryElements(
         CompilationUnitElement compilationUnit,
         LinkBuilder<tree.LibraryTag> imports) {
     measure(() {
       // TODO(lrn): Possibly recursively handle 'part' directives in patch.
       leg.Script script = compilationUnit.script;
       Token tokens = new StringScanner(script.text).tokenize();
@@ skipping 383 matching lines @@
 
 // TODO(johnniwinther): Add unittest when patch is (real) metadata.
 bool isPatchElement(Element element) {
   // TODO(lrn): More checks needed if we introduce metadata for real.
   // In that case, it must have the identifier "native" as metadata.
   for (Link link = element.metadata; !link.isEmpty; link = link.tail) {
     if (link.head is PatchMetadataAnnotation) return true;
   }
   return false;
 }