Completion with the new analysis driver.

pkg/analysis_server/lib/src/analysis_server.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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core';
 import 'dart:io' as io;
@@ skipping 567 matching lines @@
   nd.AnalysisDriver getAnalysisDriver(String path) {
     Iterable<nd.AnalysisDriver> drivers = driverMap.values;
     if (drivers.isNotEmpty) {
       return drivers.firstWhere((driver) => driver.isAddedFile(path),
           orElse: () => drivers.first);
     }
     return null;
   }
 
   /**
-   * Return the analysis result for the file with the given [path].
+   * Return the analysis result for the file with the given [path]. The file is
+   * analyzed in one of the analysis drivers to which the file was added,
+   * otherwise in the first driver, otherwise `null` is returned.
    */
   Future<nd.AnalysisResult> getAnalysisResult(String path) async {
     nd.AnalysisResult result = priorityFileResults[path];
     if (result != null) {
       return result;
     }
     nd.AnalysisDriver driver = getAnalysisDriver(path);
-    return driver.getResult(path);
+    return driver?.getResult(path);
   }
 
   CompilationUnitElement getCompilationUnitElement(String file) {
     ContextSourcePair pair = getContextSourcePair(file);
     if (pair == null) {
       return null;
     }
     // prepare AnalysisContext and Source
     AnalysisContext context = pair.context;
     Source unitSource = pair.source;
@@ skipping 1383 matching lines @@
   /**
    * The [PerformanceTag] for time spent in server request handlers.
    */
   static PerformanceTag serverRequests = new PerformanceTag('serverRequests');
 
   /**
    * The [PerformanceTag] for time spent in split store microtasks.
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }