gracefully handle internal exceptions during request

pkg/analysis_server/test/socket_server_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.socket.server;
 
 import 'dart:async';
 
 import 'mocks.dart';
 
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/socket_server.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:unittest/unittest.dart';
 
 main() {
   group('SocketServer', () {
     test('createAnalysisServer_successful',
         SocketServerTest.createAnalysisServer_successful);
     test('createAnalysisServer_alreadyStarted',
         SocketServerTest.createAnalysisServer_alreadyStarted);
+    test('requestHandler_exception', SocketServerTest.requestHandler_exception);
+    test('requestHandler_futureException',
+        SocketServerTest.requestHandler_futureException);
   });
 }
 
 class SocketServerTest {
   static Future createAnalysisServer_successful() {
     SocketServer server = new SocketServer(DirectoryBasedDartSdk.defaultSdk);
     MockServerChannel channel = new MockServerChannel();
     server.createAnalysisServer(channel);
     channel.expectMsgCount(notificationCount: 1);
     expect(channel.notificationsReceived[0].event, SERVER_CONNECTED);
@@ skipping 21 matching lines @@
         RequestErrorCode.SERVER_ALREADY_STARTED));
     channel2.sendRequest(new ServerShutdownParams().toRequest('0')).then(
         (Response response) {
       expect(response.id, equals('0'));
       expect(response.error, isNotNull);
       expect(response.error.code, equals(
           RequestErrorCode.SERVER_ALREADY_STARTED));
       channel2.expectMsgCount(responseCount: 2);
     });
   }
+
+  static Future requestHandler_exception() {
+    SocketServer server = new SocketServer(DirectoryBasedDartSdk.defaultSdk);
+    MockServerChannel channel = new MockServerChannel();
+    server.createAnalysisServer(channel);
+    _MockRequestHandler handler = new _MockRequestHandler(false);
+    server.analysisServer.handlers = [handler];
+    var request = new ServerGetVersionParams().toRequest('0');
+    return channel.sendRequest(request).then((Response response) {
+      expect(response.id, equals('0'));
+      expect(response.error, isNotNull);
+      expect(response.error.code, equals(RequestErrorCode.SERVER_ERROR));
+      channel.expectMsgCount(responseCount: 1, notificationCount: 2);
+      expect(channel.notificationsReceived[1].event, SERVER_ERROR);
+    });
+  }
+
+  static Future requestHandler_futureException() {
+    SocketServer server = new SocketServer(DirectoryBasedDartSdk.defaultSdk);
+    MockServerChannel channel = new MockServerChannel();
+    server.createAnalysisServer(channel);
+    _MockRequestHandler handler = new _MockRequestHandler(true);
+    server.analysisServer.handlers = [handler];
+    var request = new ServerGetVersionParams().toRequest('0');
+    return channel.sendRequest(request).then((Response response) {
+      expect(response.id, equals('0'));
+      expect(response.error, isNull);
+      channel.expectMsgCount(responseCount: 1, notificationCount: 2);
+      expect(channel.notificationsReceived[1].event, SERVER_ERROR);
+    });
+  }
 }
+
+class _MockRequestHandler implements RequestHandler {
+  final bool futureException;
+
+  _MockRequestHandler(this.futureException);
+
+  @override
+  Response handleRequest(Request request) {
+    if (futureException) {
+      new Future(throwException);
+      return new Response(request.id);
+    }
+    throw 'mock request exception';
+  }
+
+  void throwException() {
+    throw 'mock future exception';
+  }
+}