discard code completion cache if context or other sources change

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 59d82c55b157cd216288961ee5b8e5f5843200af..a5caa95307b5190f373218a3c13335728d105353 100644
--- a/pkg/analysis_server/test/domain_completion_test.dart
+++ b/pkg/analysis_server/test/domain_completion_test.dart
@@ -6,11 +6,17 @@ library test.domain.completion;
 
 import 'dart:async';
 
+import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
+import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analysis_server/src/domain_completion.dart';
 import 'package:analysis_server/src/protocol.dart';
+import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/index/index.dart' show Index;
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
+import 'package:analysis_server/src/services/search/search_engine.dart';
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/source.dart';
 import 'package:unittest/unittest.dart';
 
 import 'analysis_abstract.dart';
@@ -19,10 +25,155 @@ import 'reflective_tests.dart';
 
 main() {
   groupSep = ' | ';
+  runReflectiveTests(CompletionCacheTest);
   runReflectiveTests(CompletionTest);
 }
 
 @ReflectiveTestCase()
+class CompletionCacheTest extends AbstractAnalysisTest {
+  AnalysisDomainHandler analysisDomain;
+
+  @override
+  void setUp() {
+    super.setUp();
+    createProject();
+    analysisDomain = handler;
+    handler = new Test_CompletionDomainHandler(server);
+  }
+
+  void tearDown() {
+    super.tearDown();
+    analysisDomain = null;
+  }
+
+  test_cache() {
+    Test_CompletionDomainHandler target = handler;
+    addTestFile('^library A; cl');
+    Request request =
+        new CompletionGetSuggestionsParams(testFile, 0).toRequest('0');
+
+    /*
+     * Assert cache is created by manager
+     * and context.onSourceChanged listen is called
+     */
+    Source source;
+    var expectedCache = null;
+    handleSuccessfulRequest(request);
+    return pumpEventQueue().then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expect(target.completionManager.computeCallCount, 1);
+      source = target.completionManager.source;
+      expect(source, isNotNull);
+      expectedCache = target.completionManager.cache;
+      expect(expectedCache, isNotNull);
+      expect(target.mockContext.mockStream.listenCount, 1);
+      expect(target.mockContext.mockStream.cancelCount, 0);
+
+      /*
+       * Assert cache is stored in target,
+       * and context.onSourceChanged listen has not changed
+       */
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 1);
+      expect(target.mockContext.mockStream.cancelCount, 0);
+
+      /*
+       * Assert same cache and listening is preserved across multiple calls
+       */
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 1);
+      expect(target.mockContext.mockStream.cancelCount, 0);
+
+      /*
+       * Trigger source change event that should NOT clear existing cache
+       */
+      target.sourcesChanged(new SourcesChangedEvent.changedContent(source, ''));
+    }).then((_) {
+
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 1);
+      expect(target.mockContext.mockStream.cancelCount, 0);
+
+      /*
+       * Trigger source change event that should clear existing cache
+       * and assert subscription.cancel is called when the cache is discarded.
+       */
+      ChangeSet changeSet = new ChangeSet();
+      changeSet.removedSource(source);
+      target.sourcesChanged(new SourcesChangedEvent(changeSet));
+    }).then((_) {
+      expect(target.mockContext.mockStream.listenCount, 1);
+      expect(target.mockContext.mockStream.cancelCount, 1);
+
+      /*
+       * Assert that cache was cleared, recreated,
+       * and context.onSourceChanged listen is called again.
+       */
+      expectedCache = null;
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expectedCache = target.completionManager.cache;
+      expect(expectedCache, isNotNull);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 2);
+      expect(target.mockContext.mockStream.cancelCount, 1);
+
+      /*
+       * Assert same cache and listening is preserved across multiple calls
+       */
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 2);
+      expect(target.mockContext.mockStream.cancelCount, 1);
+
+      /*
+       * Trigger context change event that should clear existing cache
+       */
+      Request request =
+          new AnalysisSetAnalysisRootsParams([], []).toRequest('0');
+      Response response = analysisDomain.handleRequest(request);
+      expect(response, isResponseSuccess('0'));
+      return pumpEventQueue();
+    }).then((_) {
+      expect(target.mockContext.mockStream.listenCount, 2);
+      expect(target.mockContext.mockStream.cancelCount, 2);
+
+      /*
+       * Assert that cache was cleared, recreated,
+       * and context.onSourceChanged listen is called again.
+       */
+      expectedCache = null;
+      handleSuccessfulRequest(request);
+      return pumpEventQueue();
+    }).then((_) {
+      expect(identical(target.cacheReceived, expectedCache), isTrue);
+      expectedCache = target.completionManager.cache;
+      expect(expectedCache, isNotNull);
+      expect(target.completionManager.computeCallCount, 1);
+      expect(target.mockContext.mockStream.listenCount, 3);
+      expect(target.mockContext.mockStream.cancelCount, 2);
+    });
+  }
+}
+
+@ReflectiveTestCase()
 class CompletionTest extends AbstractAnalysisTest {
   String completionId;
   int completionOffset;
@@ -211,3 +362,129 @@ class CompletionTest extends AbstractAnalysisTest {
     });
   }
 }
+
+class MockCache extends CompletionCache {
+  MockCache(AnalysisContext context, Source source) : super(context, source);
+}
+
+class MockCompletionManager implements CompletionManager {
+  final AnalysisContext context;
+  final Source source;
+  final int offset;
+  final SearchEngine searchEngine;
+  CompletionCache cache;
+  CompletionPerformance performance;
+  StreamController<CompletionResult> controller;
+  int computeCallCount = 0;
+
+  MockCompletionManager(this.context, this.source, this.offset,
+      this.searchEngine, this.cache, this.performance);
+
+  @override
+  CompletionCache get completionCache {
+    if (cache == null) {
+      cache = new MockCache(context, source);
+    }
+    return cache;
+  }
+
+  @override
+  void compute() {
+    ++computeCallCount;
+    CompletionResult result = new CompletionResult(0, 0, [], true);
+    controller.add(result);
+  }
+
+  @override
+  Stream<CompletionResult> results() {
+    controller = new StreamController<CompletionResult>(onListen: () {
+      scheduleMicrotask(compute);
+    });
+    return controller.stream;
+  }
+}
+
+/**
+ * Mock [AnaysisContext] for tracking usage of onSourcesChanged.
+ */
+class MockContext implements AnalysisContext {
+  MockStream<SourcesChangedEvent> mockStream;
+
+  MockContext() {
+    mockStream = new MockStream<SourcesChangedEvent>();
+  }
+
+  @override
+  Stream<SourcesChangedEvent> get onSourcesChanged => mockStream;
+
+  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+/**
+ * Mock stream for tracking calls to listen and subscription.cancel.
+ */
+class MockStream<E> implements Stream<E> {
+  MockSubscription<E> mockSubscription = new MockSubscription<E>();
+  int listenCount = 0;
+
+  int get cancelCount => mockSubscription.cancelCount;
+
+  @override
+  StreamSubscription<E> listen(void onData(E event), {Function onError, void
+      onDone(), bool cancelOnError}) {
+    ++listenCount;
+    return mockSubscription;
+  }
+
+  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+/**
+ * Mock subscription for tracking calls to subscription.cancel.
+ */
+class MockSubscription<E> implements StreamSubscription<E> {
+  int cancelCount = 0;
+
+  Future cancel() {
+    ++cancelCount;
+    return new Future.value(true);
+  }
+
+  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+/**
+ * A [CompletionDomainHandler] subclass that returns a mock completion manager
+ * so that the domain handler cache management can be tested.
+ */
+class Test_CompletionDomainHandler extends CompletionDomainHandler {
+  CompletionCache cacheReceived;
+  final MockContext mockContext = new MockContext();
+  MockCompletionManager completionManager;
+
+  Test_CompletionDomainHandler(AnalysisServer server) : super(server);
+
+  void contextsChanged(ContextsChangedEvent event) {
+    if (event.removed.length == 1) {
+      event = new ContextsChangedEvent(
+          added: event.added,
+          changed: event.changed,
+          removed: [mockContext]);
+    }
+    super.contextsChanged(event);
+  }
+
+  CompletionManager createCompletionManager(AnalysisContext context,
+      Source source, int offset, SearchEngine searchEngine, CompletionCache cache,
+      CompletionPerformance performance) {
+    cacheReceived = cache;
+    completionManager = new MockCompletionManager(
+        mockContext,
+        source,
+        offset,
+        searchEngine,
+        cache,
+        performance);
+    return completionManager;
+  }
+}