If the state location is not accessible, use MemoryByteStore.

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 362 matching lines @@
       if (name != null) {
         if (name == 'stdout') {
           sink = io.stdout;
         } else if (name.startsWith('file:')) {
           String path = name.substring('file:'.length);
           sink = new io.File(path).openWrite(mode: io.FileMode.APPEND);
         }
       }
       _analysisPerformanceLogger = new nd.PerformanceLog(sink);
     }
-    if (resourceProvider is PhysicalResourceProvider) {
-      byteStore = new MemoryCachingByteStore(
-          new EvictingFileByteStore(
-              resourceProvider.getStateLocation('.analysis-driver').path,
-              1024 * 1024 * 1024 /*1 GiB*/),
-          64 * 1024 * 1024 /*64 MiB*/);
-    } else {
-      byteStore = new MemoryByteStore();
-    }
+    byteStore = _createByteStore();
     analysisDriverScheduler =
         new nd.AnalysisDriverScheduler(_analysisPerformanceLogger);
     analysisDriverScheduler.status.listen(sendStatusNotificationNew);
     analysisDriverScheduler.start();
 
     if (useSingleContextManager) {
       contextManager = new SingleContextManager(resourceProvider, sdkManager,
           packageResolverProvider, analyzedFilesGlobs, defaultContextOptions);
     } else {
       contextManager = new ContextManagerImpl(
@@ skipping 428 matching lines @@
       unit = result?.unit;
     } else {
       unit = await getResolvedCompilationUnit(file);
     }
     if (unit != null) {
       return new NodeLocator(offset).searchWithin(unit);
     }
     return null;
   }
 
-// TODO(brianwilkerson) Add the following method after 'prioritySources' has
-// been added to InternalAnalysisContext.
-//  /**
-//   * Return a list containing the full names of all of the sources that are
-//   * priority sources.
-//   */
-//  List<String> getPriorityFiles() {
-//    List<String> priorityFiles = new List<String>();
-//    folderMap.values.forEach((ContextDirectory directory) {
-//      InternalAnalysisContext context = directory.context;
-//      context.prioritySources.forEach((Source source) {
-//        priorityFiles.add(source.fullName);
-//      });
-//    });
-//    return priorityFiles;
-//  }
-
   /**
    * Return a [Future] that completes with the resolved [CompilationUnit] for
    * the Dart file with the given [path], or with `null` if the file is not a
    * Dart file or cannot be resolved.
    */
   Future<CompilationUnit> getResolvedCompilationUnit(String path) async {
     if (options.enableNewAnalysisDriver) {
       nd.AnalysisResult result = await getAnalysisResult(path);
       return result?.unit;
     }
     ContextSourcePair contextSource = getContextSourcePair(path);
     AnalysisContext context = contextSource.context;
     if (context == null) {
       return null;
     }
     return runWithActiveContext(context, () {
       Source unitSource = contextSource.source;
       List<Source> librarySources = context.getLibrariesContaining(unitSource);
       for (Source librarySource in librarySources) {
         return context.resolveCompilationUnit2(unitSource, librarySource);
       }
       return null;
     });
   }
 
+// TODO(brianwilkerson) Add the following method after 'prioritySources' has
+// been added to InternalAnalysisContext.
+//  /**
+//   * Return a list containing the full names of all of the sources that are
+//   * priority sources.
+//   */
+//  List<String> getPriorityFiles() {
+//    List<String> priorityFiles = new List<String>();
+//    folderMap.values.forEach((ContextDirectory directory) {
+//      InternalAnalysisContext context = directory.context;
+//      context.prioritySources.forEach((Source source) {
+//        priorityFiles.add(source.fullName);
+//      });
+//    });
+//    return priorityFiles;
+//  }
+
   /**
    * Handle a [request] that was read from the communication channel.
    */
   void handleRequest(Request request) {
     _performance.logRequest(request);
     runZoned(() {
       ServerPerformanceStatistics.serverRequests.makeCurrentWhile(() {
         int count = handlers.length;
         for (int i = 0; i < count; i++) {
           try {
@@ skipping 766 matching lines @@
 
   void _computingPackageMap(bool computing) {
     if (serverServices.contains(ServerService.STATUS)) {
       PubStatus pubStatus = new PubStatus(computing);
       ServerStatusParams params = new ServerStatusParams(pub: pubStatus);
       sendNotification(params.toNotification());
     }
   }
 
   /**
+   * If the state location can be accessed, return the file byte store,
+   * otherwise return the memory byte store.
+   */
+  ByteStore _createByteStore() {
+    const int M = 1024 * 1024 /*1 MiB*/;
+    const int G = 1024 * 1024 * 1024 /*1 GiB*/;
+    if (resourceProvider is PhysicalResourceProvider) {
+      Folder stateLocation =
+          resourceProvider.getStateLocation('.analysis-driver');
+      if (stateLocation != null) {
+        return new MemoryCachingByteStore(
+            new EvictingFileByteStore(stateLocation.path, G), 64 * M);
+      }
+    }
+    return new MemoryCachingByteStore(new NullByteStore(), 64 * M);
+  }
+
+  /**
    * Return a set of all contexts whose associated folder is contained within,
    * or equal to, one of the resources in the given list of [resources].
    */
   Set<AnalysisContext> _getContexts(List<Resource> resources) {
     Set<AnalysisContext> contexts = new HashSet<AnalysisContext>();
     resources.forEach((Resource resource) {
       if (resource is Folder) {
         contexts.addAll(contextManager.contextsInAnalysisRoot(resource));
       }
     });
@@ skipping 449 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');
 }