Add defaultCompletionSorter allowing sorting to be overridden - fixes #24339

pkg/analysis_server/lib/src/services/completion/common_usage_computer.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.computer.dart.relevance;
 
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analysis_server/src/protocol_server.dart'
     show CompletionSuggestion, CompletionSuggestionKind;
+import 'package:analysis_server/src/services/completion/contribution_sorter.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 
 part 'common_usage_generated.dart';
 
 /**
  * A computer for adjusting the relevance of completions computed by others
- * based upon common Dart usage patterns.
+ * based upon common Dart usage patterns. This is a long-lived object
+ * that should not maintain state between calls to it's [sort] method.
  */
-class CommonUsageComputer {
+class CommonUsageComputer implements ContributionSorter {
   /**
    * A map of <library>.<classname> to an ordered list of method names,
    * field names, getter names, and named constructors.
    * The names are ordered from most relevant to least relevant.
    * Names not listed are considered equally less relevant than those listed.
    */
   Map<String, List<String>> selectorRelevance;
 
   CommonUsageComputer([this.selectorRelevance = defaultSelectorRelevance]);
 
-  /**
-   * Adjusts the relevance based on the given completion context.
-   * The compilation unit and completion node
-   * in the given completion context may not be resolved.
-   * This method should execute quickly and not block waiting for any analysis.
-   */
-  void computeFast(DartCompletionRequest request) {
+  @override
+  void sort(DartCompletionRequest request) {
     _update(request);
   }
 
-  /**
-   * Adjusts the relevance based on the given completion context.
-   * The compilation unit and completion node
-   * in the given completion context are resolved.
-   */
-  void computeFull(DartCompletionRequest request) {
-    _update(request);
-  }
-
   /**
    * Adjusts the relevance based on the given completion context.
    * The compilation unit and completion node
    * in the given completion context may not be resolved.
    */
   void _update(DartCompletionRequest request) {
     var visitor = new _BestTypeVisitor(request.target.entity);
     DartType type = request.target.containingNode.accept(visitor);
     if (type != null) {
       Element typeElem = type.element;
@@ skipping 76 matching lines @@
   DartType visitPropertyAccess(PropertyAccess node) {
     if (node.propertyName == entity) {
       Expression target = node.realTarget;
       if (target != null) {
         return target.bestType;
       }
     }
     return null;
   }
 }