Make NavigationOperation a MergeableOperation.

pkg/analysis_server/test/operation/operation_queue_test.dart

Index: pkg/analysis_server/test/operation/operation_queue_test.dart
diff --git a/pkg/analysis_server/test/operation/operation_queue_test.dart b/pkg/analysis_server/test/operation/operation_queue_test.dart
index 0be1a738121b5ebd8131000c2d01677146a67940..ed7fbcaa117abb07fcd6ef6783ed7183f62316f9 100644
--- a/pkg/analysis_server/test/operation/operation_queue_test.dart
+++ b/pkg/analysis_server/test/operation/operation_queue_test.dart
@@ -60,6 +60,23 @@ class ServerContextManagerMock extends TypedMock implements ContextManager {
 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);
@@ -106,6 +123,20 @@ class ServerOperationQueueTest {
     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();
@@ -180,6 +211,27 @@ class ServerOperationQueueTest {
     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 {