Fix error handling for formatting and update the spec

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/edit/assist/assist_core.dart';
 import 'package:analysis_server/edit/fix/fix_core.dart';
@@ skipping 80 matching lines @@
       start = null;
       length = null;
     }
 
     SourceCode code = new SourceCode(unformattedSource,
         uri: null,
         isCompilationUnit: true,
         selectionStart: start,
         selectionLength: length);
     DartFormatter formatter = new DartFormatter();
-    SourceCode formattedResult = formatter.formatSource(code);
+    SourceCode formattedResult;
+    try {
+      formattedResult = formatter.formatSource(code);
+    } on FormatterException {
+      return new Response.formatWithErrors(request);
+    }
     String formattedSource = formattedResult.text;
 
     List<SourceEdit> edits = <SourceEdit>[];
 
     if (formattedSource != unformattedSource) {
       //TODO: replace full replacements with smaller, more targeted edits
       SourceEdit edit =
           new SourceEdit(0, unformattedSource.length, formattedSource);
       edits.add(edit);
     }
 
     int newStart = formattedResult.selectionStart;
     int newLength = formattedResult.selectionLength;
 
     // Sending null start/length values would violate protocol, so convert back
     // to 0.
     if (newStart == null) {
       newStart = 0;
     }
     if (newLength == null) {
       newLength = 0;
     }
 
-    return new EditFormatResult(edits, newStart,
-        newLength).toResponse(request.id);
+    return new EditFormatResult(edits, newStart, newLength)
+        .toResponse(request.id);
   }
 
   Response getAssists(Request request) {
     EditGetAssistsParams params = new EditGetAssistsParams.fromRequest(request);
     ContextSourcePair pair = server.getContextSourcePair(params.file);
     engine.AnalysisContext context = pair.context;
     Source source = pair.source;
     List<SourceChange> changes = <SourceChange>[];
     if (context != null && source != null) {
-      List<Assist> assists = computeAssists(plugin, context,
-          source, params.offset, params.length);
+      List<Assist> assists =
+          computeAssists(plugin, context, source, params.offset, params.length);
       assists.forEach((Assist assist) {
         changes.add(assist.change);
       });
     }
     return new EditGetAssistsResult(changes).toResponse(request.id);
   }
 
   Response getFixes(Request request) {
     var params = new EditGetFixesParams.fromRequest(request);
     String file = params.file;
@@ skipping 497 matching lines @@
     }
     if (refactoring is RenameRefactoring) {
       RenameRefactoring renameRefactoring = refactoring;
       RenameOptions renameOptions = params.options;
       renameRefactoring.newName = renameOptions.newName;
       return renameRefactoring.checkNewName();
     }
     return new RefactoringStatus();
   }
 }