Catch exceptions in refactorings and return them as a SERVER_ERROR.

pkg/analysis_server/lib/src/edit/edit_domain.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 edit.domain;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
 import 'package:analysis_server/src/services/correction/assist.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/correction/sort_members.dart';
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:analysis_server/src/services/refactoring/refactoring.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart' as engine;
 import 'package:analyzer/src/generated/error.dart' as engine;
 import 'package:analyzer/src/generated/parser.dart' as engine;
 import 'package:analyzer/src/generated/scanner.dart' as engine;
 import 'package:analyzer/src/generated/source.dart';
 
 
 /**
+ * This flag is used in tests to check behavior when an exception happens
+ * inside a refactoring.
+ */
+bool test_simulateRefactoringException = false;
+
+
+/**
  * Instances of the class [EditDomainHandler] implement a [RequestHandler]
  * that handles requests in the edit domain.
  */
 class EditDomainHandler implements RequestHandler {
   /**
    * The analysis server that is using this handler to process requests.
    */
   final AnalysisServer server;
 
   /**
@@ skipping 240 matching lines @@
         if (_hasFatalError) {
           return _sendResultResponse();
         }
         // create change
         return refactoring.createChange().then((change) {
           result.change = change;
           result.potentialEdits = nullIfEmpty(refactoring.potentialEditIds);
           return _sendResultResponse();
         });
       });
+    }).catchError((exception, stackTrace) {
+      _reset();
+      server.sendResponse(
+          new Response.serverError(request, exception, stackTrace));
     });
   }
 
   /**
    * Initializes this context to perform a refactoring with the specified
    * parameters. The existing [Refactoring] is reused or created as needed.
    */
   Future<RefactoringStatus> _init(RefactoringKind kind, String file, int offset,
       int length) {
     // check if we can continue with the existing Refactoring instance
     if (this.kind == kind &&
         this.file == file &&
         this.offset == offset &&
         this.length == length) {
       return new Future.value(initStatus);
     }
     _reset();
     this.kind = kind;
     this.file = file;
     this.offset = offset;
     this.length = length;
+    // simulate an exception
+    if (test_simulateRefactoringException) {
+      throw 'A simulated refactoring exception.';
+    }
     // create a new Refactoring instance
     if (kind == RefactoringKind.CONVERT_GETTER_TO_METHOD) {
       List<Element> elements = server.getElementsAtOffset(file, offset);
       if (elements.isNotEmpty) {
         Element element = elements[0];
         if (element is ExecutableElement) {
           refactoring =
               new ConvertGetterToMethodRefactoring(searchEngine, element);
         }
       }
@@ skipping 181 matching lines @@
     }
     if (refactoring is RenameRefactoring) {
       RenameRefactoring renameRefactoring = refactoring;
       RenameOptions renameOptions = params.options;
       renameRefactoring.newName = renameOptions.newName;
       return renameRefactoring.checkNewName();
     }
     return new RefactoringStatus();
   }
 }