Handle a failure in "pub list-package-dirs".

pkg/analysis_server/test/context_directory_manager_test.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 test.context.directory.manager;
 
 import 'mocks.dart';
 import 'package:analysis_server/src/context_directory_manager.dart';
 import 'package:analysis_server/src/package_map_provider.dart';
 import 'package:analysis_server/src/resource.dart';
@@ skipping 97 matching lines @@
       Folder packageFolder = resourceProvider.newFolder(packagePath);
       packageMapProvider.packageMap = {'foo': [packageFolder]};
       manager.setRoots(<String>[projPath], <String>[]);
       expect(manager.currentContextPackageMaps[projPath],
           equals(packageMapProvider.packageMap));
     });
 
     test('add folder without pubspec', () {
       String projPath = '/my/proj';
       resourceProvider.newFolder(projPath);
+      packageMapProvider.packageMap = null;
       manager.setRoots(<String>[projPath], <String>[]);
       expect(manager.currentContextPaths, hasLength(1));
       expect(manager.currentContextPaths, contains(projPath));
       expect(manager.currentContextFilePaths[projPath], hasLength(0));
     });
 
     test('add folder with dart file', () {
       String projPath = '/my/proj';
       resourceProvider.newFolder(projPath);
       String filePath = posix.join(projPath, 'foo.dart');
@@ skipping 22 matching lines @@
       resourceProvider.newFile(pubspecPath, 'pubspec');
       manager.setRoots(<String>[projPath], <String>[]);
       manager.setRoots(<String>[], <String>[]);
       expect(manager.currentContextPaths, hasLength(0));
       expect(manager.currentContextFilePaths, hasLength(0));
     });
 
     test('remove folder without pubspec', () {
       String projPath = '/my/proj';
       resourceProvider.newFolder(projPath);
+      packageMapProvider.packageMap = null;
       manager.setRoots(<String>[projPath], <String>[]);
       manager.setRoots(<String>[], <String>[]);
       expect(manager.currentContextPaths, hasLength(0));
       expect(manager.currentContextFilePaths, hasLength(0));
     });
 
     test('ignore files in packages dir', () {
       String projPath = '/my/proj';
       resourceProvider.newFolder(projPath);
       String pubspecPath = posix.join(projPath, 'pubspec.yaml');
@@ skipping 70 matching lines @@
       test('Modify package map dependency', () {
         String dependencyPath = posix.join(projPath, 'dep');
         resourceProvider.newFile(dependencyPath, 'contents');
         String dartFilePath = posix.join(projPath, 'main.dart');
         resourceProvider.newFile(dartFilePath, 'contents');
         packageMapProvider.dependencies.add(dependencyPath);
         manager.setRoots(<String>[projPath], <String>[]);
         expect(manager.currentContextPackageMaps[projPath],
             equals(packageMapProvider.packageMap));
         String packagePath = '/package/foo';
-        resourceProvider.newFolder(projPath);
+        resourceProvider.newFolder(packagePath);
         packageMapProvider.packageMap = {'foo': projPath};
         // Changing a .dart file in the project shouldn't cause a new
         // package map to be picked up.
         resourceProvider.modifyFile(dartFilePath, 'new contents');
         return pumpEventQueue().then((_) {
           expect(manager.currentContextPackageMaps[projPath], isEmpty);
           // However, changing the package map dependency should.
           resourceProvider.modifyFile(dependencyPath, 'new contents');
           return pumpEventQueue().then((_) {
             expect(manager.currentContextPackageMaps[projPath],
                 equals(packageMapProvider.packageMap));
           });
         });
       });
+
+      test('Modify package map dependency - packageMapProvider failure', () {
+        String dependencyPath = posix.join(projPath, 'dep');
+        resourceProvider.newFile(dependencyPath, 'contents');
+        String dartFilePath = posix.join(projPath, 'main.dart');
+        resourceProvider.newFile(dartFilePath, 'contents');
+        packageMapProvider.dependencies.add(dependencyPath);
+        manager.setRoots(<String>[projPath], <String>[]);
+        expect(manager.currentContextPackageMaps[projPath],
+            equals(packageMapProvider.packageMap));
+        // Change the package map dependency so that the packageMapProvider is
+        // re-run, and arrange for it to return null from computePackageMap().
+        packageMapProvider.packageMap = null;
+        resourceProvider.modifyFile(dependencyPath, 'new contents');
+        return pumpEventQueue().then((_) {
+          // The package map should have been changed to null.
+          expect(manager.currentContextPackageMaps[projPath], isNull);
+        });
+      });
     });
   });
 }