add file watching support

pkg/analyzer/test/file_system/physical_resource_provider_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.physical_file_system;
 
 import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 268 matching lines @@
     String idOne = 'one';
     Folder folderOne = provider.getStateLocation(idOne);
     expect(folderOne, isNotNull);
     String idTwo = 'two';
     Folder folderTwo = provider.getStateLocation(idTwo);
     expect(folderTwo, isNotNull);
     expect(folderTwo, isNot(equals(folderOne)));
     expect(provider.getStateLocation(idOne), equals(folderOne));
   }
 
-  test_watch_createFile() {
+  test_watchFile_delete() {
+    var path = join(tempPath, 'foo');
+    var file = new io.File(path);
+    file.writeAsStringSync('contents 1');
+    return _watchingFile(path, (changesReceived) {
+      expect(changesReceived, hasLength(0));
+      file.deleteSync();
+      return _delayed(() {
+        expect(changesReceived, hasLength(1));
+        expect(changesReceived[0].type, equals(ChangeType.REMOVE));
+        expect(changesReceived[0].path, equals(path));
+      });
+    });
+  }
+
+  test_watchFile_modify() {
+    var path = join(tempPath, 'foo');
+    var file = new io.File(path);
+    file.writeAsStringSync('contents 1');
+    return _watchingFile(path, (changesReceived) {
+      expect(changesReceived, hasLength(0));
+      file.writeAsStringSync('contents 2');
+      return _delayed(() {
+        expect(changesReceived, hasLength(1));
+        expect(changesReceived[0].type, equals(ChangeType.MODIFY));
+        expect(changesReceived[0].path, equals(path));
+      });
+    });
+  }
+
+  test_watchFolder_createFile() {
     return _watchingFolder(tempPath, (changesReceived) {
       expect(changesReceived, hasLength(0));
       var path = join(tempPath, 'foo');
       new io.File(path).writeAsStringSync('contents');
       return _delayed(() {
         // There should be an "add" event indicating that the file was added.
         // Depending on how long it took to write the contents, it may be
         // followed by "modify" events.
         expect(changesReceived, isNotEmpty);
         expect(changesReceived[0].type, equals(ChangeType.ADD));
         expect(changesReceived[0].path, equals(path));
         for (int i = 1; i < changesReceived.length; i++) {
           expect(changesReceived[i].type, equals(ChangeType.MODIFY));
           expect(changesReceived[i].path, equals(path));
         }
       });
     });
   }
 
-  test_watch_deleteFile() {
+  test_watchFolder_deleteFile() {
     var path = join(tempPath, 'foo');
     var file = new io.File(path);
     file.writeAsStringSync('contents 1');
     return _watchingFolder(tempPath, (changesReceived) {
       expect(changesReceived, hasLength(0));
       file.deleteSync();
       return _delayed(() {
         expect(changesReceived, hasLength(1));
         expect(changesReceived[0].type, equals(ChangeType.REMOVE));
         expect(changesReceived[0].path, equals(path));
       });
     });
   }
 
-  test_watch_modifyFile() {
+  test_watchFolder_modifyFile() {
     var path = join(tempPath, 'foo');
     var file = new io.File(path);
     file.writeAsStringSync('contents 1');
     return _watchingFolder(tempPath, (changesReceived) {
       expect(changesReceived, hasLength(0));
       file.writeAsStringSync('contents 2');
       return _delayed(() {
         expect(changesReceived, hasLength(1));
         expect(changesReceived[0].type, equals(ChangeType.MODIFY));
         expect(changesReceived[0].path, equals(path));
       });
     });
   }
 
-  test_watch_modifyFile_inSubDir() {
+  test_watchFolder_modifyFile_inSubDir() {
     var subdirPath = join(tempPath, 'foo');
     new io.Directory(subdirPath).createSync();
     var path = join(tempPath, 'bar');
     var file = new io.File(path);
     file.writeAsStringSync('contents 1');
     return _watchingFolder(tempPath, (changesReceived) {
       expect(changesReceived, hasLength(0));
       file.writeAsStringSync('contents 2');
       return _delayed(() {
         expect(changesReceived, hasLength(1));
         expect(changesReceived[0].type, equals(ChangeType.MODIFY));
         expect(changesReceived[0].path, equals(path));
       });
     });
   }
 
   Future _delayed(computation()) {
     // Give the tests 1 second to detect the changes. While it may only
     // take up to a few hundred ms, a whole second gives a good margin
     // for when running tests.
     return new Future.delayed(new Duration(seconds: 1), computation);
   }
 
+  _watchingFile(String path, test(List<WatchEvent> changesReceived)) {
+    // Delay before we start watching the file.  This is necessary
+    // because on MacOS, file modifications that occur just before we
+    // start watching are sometimes misclassified as happening just after
+    // we start watching.
+    return _delayed(() {
+      File file = PhysicalResourceProvider.INSTANCE.getResource(path);
+      var changesReceived = <WatchEvent>[];
+      var subscription = file.changes.listen(changesReceived.add);
+      // Delay running the rest of the test to allow file.changes propogate.
+      return _delayed(() => test(changesReceived)).whenComplete(() {
+        subscription.cancel();
+      });
+    });
+  }
+
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     // Delay before we start watching the folder.  This is necessary
     // because on MacOS, file modifications that occur just before we
     // start watching are sometimes misclassified as happening just after
     // we start watching.
     return _delayed(() {
       Folder folder = PhysicalResourceProvider.INSTANCE.getResource(path);
       var changesReceived = <WatchEvent>[];
       var subscription = folder.changes.listen(changesReceived.add);
       // Delay running the rest of the test to allow folder.changes to
@@ skipping 13 matching lines @@
 
   setUp() {
     tempDirectory = io.Directory.systemTemp.createTempSync('test_resource');
     tempPath = tempDirectory.absolute.path;
   }
 
   tearDown() {
     tempDirectory.deleteSync(recursive: true);
   }
 }