gracefully handle internal exceptions during request

pkg/analysis_server/lib/src/analysis_server.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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 371 matching lines @@
 //        priorityFiles.add(source.fullName);
 //      });
 //    });
 //    return priorityFiles;
 //  }
 
   /**
    * Handle a [request] that was read from the communication channel.
    */
   void handleRequest(Request request) {
-    int count = handlers.length;
-    for (int i = 0; i < count; i++) {
-      try {
-        Response response = handlers[i].handleRequest(request);
-        if (response == Response.DELAYED_RESPONSE) {
+    runZoned(() {
+      int count = handlers.length;
+      for (int i = 0; i < count; i++) {
+        try {
+          Response response = handlers[i].handleRequest(request);
+          if (response == Response.DELAYED_RESPONSE) {
+            return;
+          }
+          if (response != null) {
+            channel.sendResponse(response);
+            return;
+          }
+        } on RequestFailure catch (exception) {
+          channel.sendResponse(exception.response);
           return;
-        }
-        if (response != null) {
+        } catch (exception, stackTrace) {
+          _sendServerErrorNotification(exception, stackTrace);

[Brian Wilkerson, 2014/09/11 22:48:07]

Does this mean that we are sending a notification AND a response with the same
error information? If so, that seems wrong.

[danrubel, 2014/09/11 23:32:08]

They are different. Notification is structured to include a stack trace and is
standard mechanism for returning internal errors. Response just indicates that
the request failed for some unknown reason. We can remove the response entirely,
but it seemed correct to complete the outstanding request so that the client is
not left hanging.

+          RequestError error =
+              new RequestError(RequestErrorCode.SERVER_ERROR, 'Server Error');
+          Response response = new Response(request.id, error: error);
           channel.sendResponse(response);
           return;
         }
-      } on RequestFailure catch (exception) {
-        channel.sendResponse(exception.response);
-        return;
       }
-    }
-    channel.sendResponse(new Response.unknownRequest(request));
+      channel.sendResponse(new Response.unknownRequest(request));
+    }, onError: _sendServerErrorNotification);
   }
 
   /**
    * Returns `true` if there is a subscription for the given [server] and [file].
    */
   bool hasAnalysisSubscription(AnalysisService service, String file) {
     Set<String> files = analysisServices[service];
     return files != null && files.contains(file);
   }
 
@@ skipping 507 matching lines @@
  * An object that is listening for lifecycle events from an analysis server.
  */
 abstract class AnalysisServerListener {
   /**
    * Analysis is complete.
    */
   void analysisComplete();
 }
 
 typedef void OptionUpdater(AnalysisOptionsImpl options);