Discard pending notifications on the same source change.

pkg/analysis_server/test/analysis/update_content_test.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 test.analysis.updateContent;
 
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:unittest/unittest.dart';
 
 import '../analysis_abstract.dart';
 import '../reflective_tests.dart';
 
 
 main() {
   groupSep = ' | ';
   runReflectiveTests(UpdateContentTest);
 }
 
 
 @reflectiveTest
 class UpdateContentTest extends AbstractAnalysisTest {
   Map<String, List<AnalysisError>> filesErrors = {};
+  int serverErrorCount = 0;
+  int navigationCount = 0;
 
   @override
   void processNotification(Notification notification) {
     if (notification.event == ANALYSIS_ERRORS) {
       var decoded = new AnalysisErrorsParams.fromNotification(notification);
       filesErrors[decoded.file] = decoded.errors;
     }
+    if (notification.event == ANALYSIS_NAVIGATION) {
+      navigationCount++;
+    }
+    if (notification.event == SERVER_ERROR) {
+      serverErrorCount++;
+    }
+  }
+
+  test_discardNotifications_onSourceChange() async {
+    createProject();
+    addTestFile('');
+    await server.onAnalysisComplete;
+    server.setAnalysisSubscriptions({
+      AnalysisService.NAVIGATION: [testFile].toSet()
+    });
+    // update file, analyze, but don't sent notifications
+    navigationCount = 0;
+    server.updateContent('1', {
+      testFile: new AddContentOverlay('foo() {}')
+    });
+    server.test_performAllAnalysisOperations();
+    expect(serverErrorCount, 0);
+    expect(navigationCount, 0);
+    // replace the file contents,
+    // should discard any pending notification operations
+    server.updateContent('2', {
+      testFile: new AddContentOverlay('bar() {}')
+    });
+    await server.onAnalysisComplete;
+    expect(serverErrorCount, 0);
+    expect(navigationCount, 1);
   }
 
   test_illegal_ChangeContentOverlay() {
     // It should be illegal to send a ChangeContentOverlay for a file that
     // doesn't have an overlay yet.
     createProject();
     addTestFile('library foo;');
     String id = 'myId';
     try {
       server.updateContent(id, {
@@ skipping 79 matching lines @@
     filesErrors.clear();
     server.test_flushResolvedUnit(testFile);
     server.updateContent('2', {
       testFile: new ChangeContentOverlay([new SourceEdit(0, 4, 'main')])
     });
     await server.onAnalysisComplete;
     // errors should have been resent
     expect(filesErrors, isNotEmpty);
   }
 }