filter imported element suggestions to reduce number of results sent to client

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.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 services.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/arglist_computer.dart';
@@ skipping 247 matching lines @@
    * containing the cursor is to be replaced when the suggestion is applied
    * (that is, the number of characters in the existing identifier).
    */
   int replacementLength;
 
   /**
    * The list of suggestions to be sent to the client.
    */
   final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
 
+  /**
+   * Return the original text from the [replacementOffset] to the [offset]
+   * that can be used to filter the suggestions on the server side.
+   */
+  String get filterText {
+    return context.getContents(source).data.substring(replacementOffset, offset);
+  }
+
   DartCompletionRequest(this.context, this.searchEngine, this.source,
       int offset, this.cache, CompletionPerformance performance)
       : super(offset, performance);
 }
 
 /**
  * Visitor used to determine the replacement offset and length
  * based upon the cursor location.
  */
 class _ReplacementOffsetBuilder extends SimpleAstVisitor {
   final DartCompletionRequest request;
 
   _ReplacementOffsetBuilder(this.request) {
     request.replacementOffset = request.offset;
     request.replacementLength = 0;
   }
 
   visitSimpleIdentifier(SimpleIdentifier node) {
     request.replacementOffset = node.offset;
     request.replacementLength = node.length;
   }
 }