Issue 21506. Fix for adding back previously excluded resources in sub-folders.

pkg/analysis_server/test/context_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 'package:analysis_server/src/context_manager.dart';
 import 'reflective_tests.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
@@ skipping 305 matching lines @@
     // set roots
     manager.setRoots(<String>[project], <String>[file2], <String, String>{});
     manager.assertContextPaths([project]);
     manager.assertContextFiles(project, [file1]);
     // stop excluding "2"
     manager.setRoots(<String>[project], <String>[], <String, String>{});
     manager.assertContextPaths([project]);
     manager.assertContextFiles(project, [file1, file2]);
   }
 
+  void test_setRoots_exclude_sameRoot_removeExcludedFile_inFolder() {
+    // prepare paths
+    String project = '/project';
+    String file1 = '$project/bin/file1.dart';
+    String file2 = '$project/bin/file2.dart';
+    // create files
+    resourceProvider.newFile(file1, '// 1');
+    resourceProvider.newFile(file2, '// 2');
+    // set roots
+    manager.setRoots(<String>[project], <String>[file2], <String, String>{});
+    manager.assertContextPaths([project]);
+    manager.assertContextFiles(project, [file1]);
+    // stop excluding "2"
+    manager.setRoots(<String>[project], <String>[], <String, String>{});
+    manager.assertContextPaths([project]);
+    manager.assertContextFiles(project, [file1, file2]);
+  }
+
   void test_setRoots_exclude_sameRoot_removeExcludedFolder() {
     // prepare paths
     String project = '/project';
     String folderA = '$project/aaa';
     String folderB = '$project/bbb';
     String fileA = '$folderA/a.dart';
     String fileB = '$folderB/b.dart';
     // create files
     resourceProvider.newFile(fileA, 'library a;');
     resourceProvider.newFile(fileB, 'library b;');
@@ skipping 482 matching lines @@
     currentContextFilePaths.remove(path);
     currentContextPackageUriResolvers.remove(path);
   }
 
   @override
   void updateContextPackageUriResolver(Folder contextFolder,
                                        UriResolver packageUriResolver) {
     currentContextPackageUriResolvers[contextFolder.path] = packageUriResolver;
   }
 }