Make it safe to initialize the notificationManager in server

pkg/analysis_server/lib/src/plugin/notification_manager.dart

 // Copyright (c) 2017, 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.
 
 import 'dart:collection';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart' as server;
 import 'package:analysis_server/src/channel/channel.dart';
 import 'package:analysis_server/src/plugin/result_collector.dart';
 import 'package:analysis_server/src/plugin/result_converter.dart';
@@ skipping 30 matching lines @@
 
   /**
    * A list of the paths of files and directories that are excluded from
    * analysis.
    */
   List<String> excludedPaths = <String>[];
 
   /**
    * The current set of subscriptions to which the client has subscribed.
    */
-  Map<server.AnalysisService, List<String>> currentSubscriptions =
-      <server.AnalysisService, List<String>>{};
+  Map<server.AnalysisService, Set<String>> currentSubscriptions =
+      <server.AnalysisService, Set<String>>{};
 
   /**
    * The collector being used to collect the analysis errors from the plugins.
    */
   ResultCollector<List<server.AnalysisError>> errors;
 
   /**
    * The collector being used to collect the folding regions from the plugins.
    */
   ResultCollector<List<server.FoldingRegion>> folding;
@@ skipping 224 matching lines @@
    */
   void setAnalysisRoots(List<String> included, List<String> excluded) {
     includedPaths = included;
     excludedPaths = excluded;
   }
 
   /**
    * Set the current subscriptions to the given set of [newSubscriptions].
    */
   void setSubscriptions(
-      Map<server.AnalysisService, List<String>> newSubscriptions) {
+      Map<server.AnalysisService, Set<String>> newSubscriptions) {
     /**
      * Return the collector associated with the given service, or `null` if the
      * service is not handled by this manager.
      */
     ResultCollector collectorFor(server.AnalysisService service) {
       switch (service) {
         case server.AnalysisService.FOLDING:
           return folding;
         case server.AnalysisService.HIGHLIGHTS:
           return highlights;
         case server.AnalysisService.NAVIGATION:
           return navigation;
         case server.AnalysisService.OCCURRENCES:
           return occurrences;
         case server.AnalysisService.OUTLINE:
           return outlines;
       }
       return null;
     }
 
     Set<server.AnalysisService> services =
         new HashSet<server.AnalysisService>();
     services.addAll(currentSubscriptions.keys);
     services.addAll(newSubscriptions.keys);
     services.forEach((server.AnalysisService service) {
       ResultCollector collector = collectorFor(service);
       if (collector != null) {
-        List<String> currentPaths = currentSubscriptions[service];
-        List<String> newPaths = newSubscriptions[service];
+        Set<String> currentPaths = currentSubscriptions[service];
+        Set<String> newPaths = newSubscriptions[service];
         if (currentPaths == null) {
           if (newPaths == null) {
             // This should not happen.
             return;
           }
           // All of the [newPaths] need to be added.
           newPaths.forEach((String filePath) {
             collector.startCollectingFor(filePath);
           });
         } else if (newPaths == null) {
@@ skipping 41 matching lines @@
         }
       }
       return false;
     }
 
     // TODO(brianwilkerson) Return false if error notifications are globally
     // disabled.
     return isIncluded() && !isExcluded();
   }
 }