File watching compiler.

dart/pkg/dart2js_incremental/lib/watcher.dart

Index: dart/pkg/dart2js_incremental/lib/watcher.dart
diff --git a/dart/pkg/dart2js_incremental/lib/watcher.dart b/dart/pkg/dart2js_incremental/lib/watcher.dart
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+++ b/dart/pkg/dart2js_incremental/lib/watcher.dart
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+// Copyright (c) 2015, 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 dart2js_incremental.watcher;
+
+import 'dart:io';
+
+import 'dart:async';
+
+class Watcher {
+  final Set<String> _watchedDirectories = new Set<String>();
+
+  final Map<String, Set<Uri>> _watchedFiles = new Map<String, Set<Uri>>();
+
+  final Set<Uri> _changes = new Set<Uri>();
+
+  bool _hasEarlyChanges = false;
+
+  Completer<bool> _changesCompleter;
+
+  Future<bool> hasChanges() {
+    if (_changesCompleter == null && _hasEarlyChanges) {
+      return new Future.value(true);
+    }
+    _changesCompleter = new Completer<bool>();
+    return _changesCompleter.future;
+  }
+
+  void _onFileSystemEvent(FileSystemEvent event) {
+    Set<Uri> uris = _watchedFiles[event.path];
+    if (uris == null) return;
+    _changes.addAll(uris);
+    if (_changesCompleter == null) {
+      _hasEarlyChanges = true;
+    } else if (!_changesCompleter.isCompleted) {
+      _changesCompleter.complete(true);
+    }
+  }
+
+  Map<Uri, Uri> readChanges() {
+    if (_changes.isEmpty) {
+      throw new StateError("No changes");
+    }
+    Map<Uri, Uri> result = new Map<Uri, Uri>();
+    for (Uri uri in _changes) {
+      result[uri] = uri;
+    }
+    _changes.clear();
+    return result;
+  }
+
+  void watchFile(Uri uri) {
+    String realpath = new File.fromUri(uri).resolveSymbolicLinksSync();
+    _watchedFiles.putIfAbsent(realpath, () => new Set<Uri>()).add(uri);
+    Directory directory = new File(realpath).parent;
+    if (_watchedDirectories.add(directory.path)) {
+      print("Watching ${directory.path}");
+      directory.watch().listen(_onFileSystemEvent);
+    }
+  }
+}