Validate cache consistency asynchronously. Compute modification times of physical files in a separa…

pkg/analyzer/lib/file_system/physical_file_system.dart

Index: pkg/analyzer/lib/file_system/physical_file_system.dart
diff --git a/pkg/analyzer/lib/file_system/physical_file_system.dart b/pkg/analyzer/lib/file_system/physical_file_system.dart
index 9cd62b6b89ed269e9d1ad5b181643e29bbcb3d3a..cbd2b0566fd21fe3a4e84efbb7b9beda3f7fe503 100644
--- a/pkg/analyzer/lib/file_system/physical_file_system.dart
+++ b/pkg/analyzer/lib/file_system/physical_file_system.dart
@@ -12,10 +12,34 @@ import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/util/absolute_path.dart';
+import 'package:isolate/isolate_runner.dart';
 import 'package:path/path.dart';
 import 'package:watcher/watcher.dart';
 
 /**
+ * Return modification times for every file path in [paths].
+ *
+ * If a path is `null`, the modification time is also `null`.
+ *
+ * If any exception happens, the file is considered as a not existing and
+ * `-1` is its modification time.
+ */
+List<int> _pathsToTimes(List<String> paths) {
+  return paths.map((path) {
+    if (path != null) {
+      try {
+        io.File file = new io.File(path);
+        return file.lastModifiedSync().millisecondsSinceEpoch;
+      } catch (_) {
+        return -1;
+      }
+    } else {
+      return null;
+    }
+  }).toList();
+}
+
+/**
  * A `dart:io` based implementation of [ResourceProvider].
  */
 class PhysicalResourceProvider implements ResourceProvider {
@@ -31,6 +55,9 @@ class PhysicalResourceProvider implements ResourceProvider {
    */
   static final String SERVER_DIR = ".dartServer";
 
+  static _SingleIsolateRunnerProvider pathsToTimesIsolateProvider =
+      new _SingleIsolateRunnerProvider();
+
   @override
   final AbsolutePathContext absolutePathContext =
       new AbsolutePathContext(io.Platform.isWindows);
@@ -51,6 +78,15 @@ class PhysicalResourceProvider implements ResourceProvider {
   Folder getFolder(String path) => new _PhysicalFolder(new io.Directory(path));
 
   @override
+  Future<List<int>> getModificationTimes(List<Source> sources) async {
+    List<String> paths = sources
+        .map((source) => source is FileBasedSource ? source.fullName : null)
+        .toList();
+    IsolateRunner runner = await pathsToTimesIsolateProvider.get();
+    return runner.run(_pathsToTimes, paths);
+  }
+
+  @override
   Resource getResource(String path) {
     if (io.FileSystemEntity.isDirectorySync(path)) {
       return getFolder(path);
@@ -274,3 +310,33 @@ abstract class _PhysicalResource implements Resource {
   @override
   String toString() => path;
 }
+
+/**
+ * This class encapsulates logic for creating a single [IsolateRunner].
+ */
+class _SingleIsolateRunnerProvider {
+  bool _isBeenCreated = false;

[Brian Wilkerson, 2016/07/08 21:25:09]

"_is" --> "_has" || "_isBeenCreated" --> "_created"

+  IsolateRunner _runner;
+
+  /**
+   * Complete with the only [IsolateRunner] instance.
+   */
+  Future<IsolateRunner> get() async {
+    if (_runner != null) {
+      return _runner;
+    }
+    if (_isBeenCreated) {
+      Completer<IsolateRunner> completer = new Completer<IsolateRunner>();
+      new Timer.periodic(new Duration(milliseconds: 20), (Timer timer) {
+        if (_runner != null) {
+          completer.complete(_runner);
+          timer.cancel();
+        }
+      });
+      return completer.future;
+    }
+    _isBeenCreated = true;
+    _runner = await IsolateRunner.spawn();
+    return _runner;
+  }
+}