move DartCompletionSorter to dart specific contributor

pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart

 // Copyright (c) 2015, 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.manager;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart'
     show CompletionContributor, CompletionRequest;
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_plugin.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
 import 'package:analysis_server/src/services/completion/completion_core.dart';
 import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/context/context.dart'
     show AnalysisFutureHelper, AnalysisContextImpl;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisContextImpl;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/task/dart.dart';
 import 'package:analyzer/src/generated/scanner.dart';
+import 'package:analysis_server/src/services/completion/dart/contribution_sorter.dart';
+import 'package:analysis_server/src/services/completion/dart/common_usage_sorter.dart';
 
 /**
  * [DartCompletionManager] determines if a completion request is Dart specific
  * and forwards those requests to all [DartCompletionContributor]s.
  */
 class DartCompletionManager implements CompletionContributor {
+  /**
+   * The [contributionSorter] is a long-lived object that isn't allowed
+   * to maintain state between calls to [DartContributionSorter#sort(...)].
+   */
+  static DartContributionSorter contributionSorter = new CommonUsageSorter();
+
   @override
   Future<List<CompletionSuggestion>> computeSuggestions(
       CompletionRequest request) async {
     if (!AnalysisEngine.isDartFileName(request.source.shortName)) {
       return EMPTY_LIST;
     }
 
     DartCompletionRequestImpl dartRequest =
         await DartCompletionRequestImpl.from(request);
     ReplacementRange range =
         new ReplacementRange.compute(dartRequest.offset, dartRequest.target);
     (request as CompletionRequestImpl)
       ..replacementOffset = range.offset
       ..replacementLength = range.length;
 
     // Don't suggest in comments.
     if (dartRequest.target.isCommentText) {
       return EMPTY_LIST;
     }
 
     // Request Dart specific completions from each contributor
     Map<String, CompletionSuggestion> suggestionMap =
         <String, CompletionSuggestion>{};
     for (DartCompletionContributor contributor
         in dartCompletionPlugin.contributors) {
-      for (CompletionSuggestion newSuggestion
-          in await contributor.computeSuggestions(dartRequest)) {
+      List<CompletionSuggestion> contributorSuggestions =
+          await contributor.computeSuggestions(dartRequest);
+
+      for (CompletionSuggestion newSuggestion in contributorSuggestions) {
         var oldSuggestion = suggestionMap.putIfAbsent(
             newSuggestion.completion, () => newSuggestion);
         if (newSuggestion != oldSuggestion &&
             newSuggestion.relevance > oldSuggestion.relevance) {
           suggestionMap[newSuggestion.completion] = newSuggestion;
         }
       }
     }
-    return suggestionMap.values.toList();
+
+    // Adjust suggestion relevance before returning
+    List<CompletionSuggestion> suggestions = suggestionMap.values.toList();
+    await contributionSorter.sort(dartRequest, suggestions);
+    return suggestions;
   }
 }
 
 /**
  * The information about a requested list of completions within a Dart file.
  */
 class DartCompletionRequestImpl extends CompletionRequestImpl
     implements DartCompletionRequest {
   /**
    * The [LibraryElement] representing dart:core
@@ skipping 252 matching lines @@
               // Replacement range for import URI
               return new ReplacementRange(start, end - start);
             }
           }
         }
       }
     }
     return new ReplacementRange(requestOffset, 0);
   }
 }