Make NavigationOperation a MergeableOperation.

pkg/analysis_server/test/operation/operation_queue_test.dart

 // Copyright (c) 2014, 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.operation.queue;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analysis_server/src/operation/operation.dart';
 import 'package:analysis_server/src/operation/operation_analysis.dart';
@@ skipping 42 matching lines @@
 }
 
 class ServerContextManagerMock extends TypedMock implements ContextManager {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
 @reflectiveTest
 class ServerOperationQueueTest {
   ServerOperationQueue queue = new ServerOperationQueue();
 
+  void test_add_withMerge() {
+    var opA = new _MergeableOperationMock();
+    var opB = new _MergeableOperationMock();
+    var opC = new _MergeableOperationMock();
+    when(opA.merge(opC)).thenReturn(true);
+    when(opA.merge(anyObject)).thenReturn(false);
+    when(opB.merge(anyObject)).thenReturn(false);
+    when(opC.merge(anyObject)).thenReturn(false);
+    queue.add(opA);
+    queue.add(opB);
+    queue.add(opC);
+    expect(queue.take(), same(opA));
+    expect(queue.take(), same(opB));
+    // no opC, it was merged into opA
+    expect(queue.isEmpty, isTrue);
+  }
+
   void test_clear() {
     var operationA = mockOperation(ServerOperationPriority.ANALYSIS);
     var operationB = mockOperation(ServerOperationPriority.ANALYSIS_CONTINUE);
     queue.add(operationA);
     queue.add(operationB);
     // there are some operations
     expect(queue.isEmpty, false);
     // clear - no operations
     queue.clear();
     expect(queue.isEmpty, true);
@@ skipping 26 matching lines @@
   void test_isEmpty_false() {
     var operation = mockOperation(ServerOperationPriority.ANALYSIS);
     queue.add(operation);
     expect(queue.isEmpty, isFalse);
   }
 
   void test_isEmpty_true() {
     expect(queue.isEmpty, isTrue);
   }
 
+  void test_peek() {
+    var operationA = mockOperation(ServerOperationPriority.ANALYSIS);
+    var operationB = mockOperation(ServerOperationPriority.ANALYSIS);
+    queue.add(operationA);
+    queue.add(operationB);
+    expect(queue.peek(), operationA);
+    expect(queue.peek(), operationA);
+    expect(queue.peek(), operationA);
+  }
+
+  void test_peek_empty() {
+    expect(queue.peek(), isNull);
+  }
+
   void test_reschedule() {
     var prioritySource = new MockSource();
     var analysisContextA = new AnalysisContextMock();
     var analysisContextB = new AnalysisContextMock();
     var operationA = new PerformAnalysisOperation(analysisContextA, false);
     var operationB = new PerformAnalysisOperation(analysisContextB, false);
     queue.add(operationA);
     queue.add(operationB);
     // update priority sources and reschedule
     analysisContextB.prioritySources = [prioritySource];
@@ skipping 54 matching lines @@
     var operationB = mockOperation(ServerOperationPriority.ANALYSIS_CONTINUE);
     var operationC = mockOperation(ServerOperationPriority.PRIORITY_ANALYSIS);
     queue.add(operationA);
     queue.add(operationB);
     queue.add(operationC);
     expect(queue.take(), operationC);
     expect(queue.take(), operationB);
     expect(queue.take(), operationA);
     expect(queue.take(), isNull);
   }
+
+  void test_takeIf() {
+    var operationA = mockOperation(ServerOperationPriority.ANALYSIS);
+    var operationB = mockOperation(ServerOperationPriority.ANALYSIS);
+    queue.add(operationA);
+    queue.add(operationB);
+    expect(queue.takeIf((_) => false), isNull);
+    expect(queue.takeIf((operation) => operation == operationB), operationB);
+    expect(queue.takeIf((operation) => operation == operationB), isNull);
+    expect(queue.takeIf((operation) => operation == operationA), operationA);
+    expect(queue.isEmpty, isTrue);
+  }
+}
+
+class _MergeableOperationMock extends TypedMock implements MergeableOperation {
+  @override
+  ServerOperationPriority get priority {
+    return ServerOperationPriority.ANALYSIS_NOTIFICATION;
+  }
+
+  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
 class _ServerOperationMock extends TypedMock implements ServerOperation {
   final AnalysisContext context;
 
   _ServerOperationMock([this.context]);
 
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
@@ skipping 12 matching lines @@
     return ServerOperationPriority.ANALYSIS_NOTIFICATION;
   }
 
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 
   @override
   bool shouldBeDiscardedOnSourceChange(Source source) {
     return source == this.source;
   }
 }