abort completion request - fixes #24271

pkg/analysis_server/test/domain_completion_test.dart

Index: pkg/analysis_server/test/domain_completion_test.dart
diff --git a/pkg/analysis_server/test/domain_completion_test.dart b/pkg/analysis_server/test/domain_completion_test.dart
index acff0070be3084e49341b2301bf4c935140ec152..61734b6ddac1d076770436e611d2568a7a372897 100644
--- a/pkg/analysis_server/test/domain_completion_test.dart
+++ b/pkg/analysis_server/test/domain_completion_test.dart
@@ -17,6 +17,7 @@ import 'package:unittest/unittest.dart';
 
 import 'analysis_abstract.dart';
 import 'domain_completion_util.dart';
+import 'mocks.dart' show pumpEventQueue;
 import 'utils.dart';
 
 main() {
@@ -53,6 +54,76 @@ class CompletionDomainHandlerTest extends AbstractCompletionDomainTest {
     });
   }
 
+  test_imports_aborted_new_request() async {
+    addTestFile('''
+        class foo { }
+        c^''');
+
+    // Make a request for suggestions
+    Request request =
+        new CompletionGetSuggestionsParams(testFile, completionOffset)
+            .toRequest('7');
+    Response response = handleSuccessfulRequest(request);
+    var result1 = new CompletionGetSuggestionsResult.fromResponse(response);
+    var completionId1 = result1.id;
+    assertValidId(response.id);
+
+    // Perform some analysis but assert that no suggestions have yet been made
+    completionId = completionId1;
+    await pumpEventQueue(25);
+    expect(suggestionsDone, isFalse);
+    expect(suggestions, hasLength(0));
+
+    // Make another request before the first request completes
+    Request request2 =
+        new CompletionGetSuggestionsParams(testFile, completionOffset)
+            .toRequest('8');
+    Response response2 = handleSuccessfulRequest(request2);
+    var result2 = new CompletionGetSuggestionsResult.fromResponse(response2);
+    var completionId2 = result2.id;
+    assertValidId(completionId2);
+
+    // Wait for both sets of suggestions
+    completionId = completionId2;
+    await pumpEventQueue();
+    expect(allSuggestions[completionId1], hasLength(0));
+    expect(allSuggestions[completionId2], same(suggestions));
+    assertHasResult(CompletionSuggestionKind.KEYWORD, 'class',
+        relevance: DART_RELEVANCE_HIGH);
+  }
+
+  test_imports_aborted_source_changed() async {
+    addTestFile('''
+        class foo { }
+        c^''');
+
+    // Make a request for suggestions
+    Request request =
+        new CompletionGetSuggestionsParams(testFile, completionOffset)
+            .toRequest('0');
+    Response response = handleSuccessfulRequest(request);
+    completionId = response.id;
+    assertValidId(completionId);
+
+    // Perform some analysis but assert that no suggestions have yet been made
+    await pumpEventQueue(25);
+    expect(suggestionsDone, isFalse);
+    expect(suggestions, hasLength(0));
+
+    // Simulate user deleting text after request but before suggestions returned
+    server.updateContent('uc1', {testFile: new AddContentOverlay(testCode)});
+    server.updateContent('uc2', {
+      testFile: new ChangeContentOverlay(
+          [new SourceEdit(completionOffset - 1, 1, '')])
+    });
+
+    // Expect the completion domain to discard request because source changed
+    await pumpEventQueue().then((_) {
+      expect(suggestionsDone, isTrue);
+    });
+    expect(suggestions, hasLength(0));
+  }
+
   test_imports_incremental() async {
     addTestFile('''library foo;
       e^