allow client to specify any combination of add/modified/removed

pkg/analysis_server/test/protocol_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.protocol;
 
 import 'dart:convert';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 282 matching lines @@
 
   static void indexOperator_hasKey() {
     var indexResult = makeDatum({
       'foo': 'bar'
     })['foo'];
     expect(indexResult, isRequestDatum);
     expect(indexResult.datum, equals('bar'));
     expect(indexResult.path, equals('myPath.bar'));
   }
 
+  @runTest
+  static void hasKey() {
+    var datum = makeDatum({
+      'foo': 'bar'
+    });
+    expect(datum.hasKey('foo'), isTrue);
+    expect(datum.hasKey('bar'), isFalse);
+    expect(datum.hasKey('baz'), isFalse);
+  }
+
   static void forEachMap_nonMap() {
     expect(() => makeDatum(1).forEachMap((key, value) {
       fail('Non-map should not be iterated');
     }), _throwsInvalidParameter);
   }
 
   static void forEachMap_emptyMap() {
     makeDatum({}).forEachMap((key, value) {
       fail('Empty map should not be iterated');
     });
@@ skipping 174 matching lines @@
     original.setResult('foo', 'bar');
     Response response = new Response.fromJson(original.toJson());
     expect(response.id, equals('myId'));
     Map<String, Object> result = response.result;
     expect(result.length, equals(1));
     expect(result['foo'], equals('bar'));
   }
 }
 
 Matcher _throwsRequestFailure = throwsA(new isInstanceOf<RequestFailure>());