Add ApplyChangesStatus to AnalysisContext.applyChanges() and use it in DAS.

pkg/analyzer/lib/src/context/context.dart

 // 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.
 
 library analyzer.src.context.context;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
@@ skipping 504 matching lines @@
       if (level == AnalysisLevel.NONE) {
         changeSet.removedSource(source);
       } else {
         changeSet.addedSource(source);
       }
     });
     applyChanges(changeSet);
   }
 
   @override
-  void applyChanges(ChangeSet changeSet) {
+  ApplyChangesStatus applyChanges(ChangeSet changeSet) {
     if (changeSet.isEmpty) {
-      return;
+      return new ApplyChangesStatus(false);
     }
     //
     // First, compute the list of sources that have been removed.
     //
-    List<Source> removedSources =
-        new List<Source>.from(changeSet.removedSources);
+    List<Source> removedSources = changeSet.removedSources.toList();
     for (SourceContainer container in changeSet.removedContainers) {
       _addSourcesInContainer(removedSources, container);
     }
     //
     // Then determine which cached results are no longer valid.
     //
     for (Source source in changeSet.addedSources) {
       _sourceAvailable(source);
     }
-    for (Source source in changeSet.changedSources) {
-      if (_contentCache.getContents(source) != null) {
-        // This source is overridden in the content cache, so the change will
-        // have no effect. Just ignore it to avoid wasting time doing
-        // re-analysis.
-        continue;
-      }
+    // Exclude sources that are overridden in the content cache, so the change
+    // will have no effect. Just ignore it to avoid wasting time doing
+    // re-analysis.
+    List<Source> changedSources = changeSet.changedSources
+        .where((s) => _contentCache.getContents(s) == null)
+        .toList();
+    for (Source source in changedSources) {

[Brian Wilkerson, 2015/11/16 23:19:32]

I don't see why this is better. It creates more objects that need to be garbage
collected, but...

       _sourceChanged(source);
     }
     changeSet.changedContents.forEach((Source key, String value) {
       _contentsChanged(key, value, false);
     });
     changeSet.changedRanges
         .forEach((Source source, ChangeSet_ContentChange change) {
       _contentRangeChanged(source, change.contents, change.offset,
           change.oldLength, change.newLength);
     });
     for (Source source in changeSet.deletedSources) {
       _sourceDeleted(source);
     }
     for (Source source in removedSources) {
       _sourceRemoved(source);
     }
     for (WorkManager workManager in workManagers) {
       workManager.applyChange(
-          changeSet.addedSources, changeSet.changedSources, removedSources);
+          changeSet.addedSources, changedSources, removedSources);
     }
     _onSourcesChangedController.add(new SourcesChangedEvent(changeSet));
+    return new ApplyChangesStatus(changeSet.addedSources.isNotEmpty ||
+        changeSet.changedContents.isNotEmpty ||
+        changeSet.deletedSources.isNotEmpty ||
+        changedSources.isNotEmpty ||
+        removedSources.isNotEmpty);
   }
 
   @override
   String computeDocumentationComment(Element element) {
     if (element == null) {
       return null;
     }
     Source source = element.source;
     if (source == null) {
       return null;
@@ skipping 1560 matching lines @@
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new IllegalArgumentException(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(<CachePartition>[
       AnalysisEngine.instance.partitionManager_new.forSdk(sdk)
     ]);
   }
 }