Change FileStat static methods to return NOT_FOUND instead for throwing

sdk/lib/io/file_system_entity.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 class FileSystemEntityType {
   static const FILE = const FileSystemEntityType._internal(0);
   static const DIRECTORY = const FileSystemEntityType._internal(1);
   static const LINK = const FileSystemEntityType._internal(2);
@@ skipping 17 matching lines @@
  */
 class FileStat {
   // These must agree with enum FileStat in file.h.
   static const _TYPE = 0;
   static const _CHANGED_TIME = 1;
   static const _MODIFIED_TIME = 2;
   static const _ACCESSED_TIME = 3;
   static const _MODE = 4;
   static const _SIZE = 5;
 
+  static const _notFound = const FileStat._internalNotFound();
+
   /**
    * The time of the last change to the data or metadata of the file system
    * object.  On Windows platforms, this is instead the file creation time.
    */
   final DateTime changed;
   /**
    * The time of the last change to the data of the file system
    * object.
    */
   final DateTime modified;
@@ skipping 18 matching lines @@
    */
   final int size;
 
   FileStat._internal(this.changed,
                      this.modified,
                      this.accessed,
                      this.type,
                      this.mode,
                      this.size);
 
+  const FileStat._internalNotFound() :
+      changed = null,  modified = null, accessed = null,
+      type = FileSystemEntityType.NOT_FOUND, mode = 0, size = -1;
+
   external static List<int> _statSync(String path);
 
 
   /**
    * Calls the operating system's stat() function on [path].
    * Returns a [FileStat] object containing the data returned by stat().
    * If the call fails, returns a [FileStat] object with .type set to
    * FileSystemEntityType.NOT_FOUND and the other fields invalid.
    */
   static FileStat statSync(String path) {
     // Trailing path is not supported on Windows.
     if (Platform.isWindows) {
       path = FileSystemEntity._trimTrailingPathSeparators(path);
     }
     var data = _statSync(path);
-    if (data is OSError) throw data;
+    if (data is OSError) return FileStat._notFound;
     return new FileStat._internal(
         new DateTime.fromMillisecondsSinceEpoch(data[_CHANGED_TIME] * 1000),
         new DateTime.fromMillisecondsSinceEpoch(data[_MODIFIED_TIME] * 1000),
         new DateTime.fromMillisecondsSinceEpoch(data[_ACCESSED_TIME] * 1000),
         FileSystemEntityType._lookup(data[_TYPE]),
         data[_MODE],
         data[_SIZE]);
   }
 
   /**
    * Asynchronously calls the operating system's stat() function on [path].
    * Returns a Future which completes with a [FileStat] object containing
    * the data returned by stat().
    * If the call fails, completes the future with a [FileStat] object with
    * .type set to FileSystemEntityType.NOT_FOUND and the other fields invalid.
    */
   static Future<FileStat> stat(String path) {
     // Trailing path is not supported on Windows.
     if (Platform.isWindows) {
       path = FileSystemEntity._trimTrailingPathSeparators(path);
     }
     return _IOService.dispatch(_FILE_STAT, [path]).then((response) {
       if (_isErrorResponse(response)) {
-        throw _exceptionFromResponse(response,
-                                     "Error getting stat",
-                                     path);
+        return FileStat._notFound;
       }
       // Unwrap the real list from the "I'm not an error" wrapper.
       List data = response[1];
       return new FileStat._internal(
           new DateTime.fromMillisecondsSinceEpoch(data[_CHANGED_TIME] * 1000),
           new DateTime.fromMillisecondsSinceEpoch(data[_MODIFIED_TIME] * 1000),
           new DateTime.fromMillisecondsSinceEpoch(data[_ACCESSED_TIME] * 1000),
           FileSystemEntityType._lookup(data[_TYPE]),
           data[_MODE],
           data[_SIZE]);
@@ skipping 636 matching lines @@
     return buffer.toString();
   }
 }
 
 
 class _FileSystemWatcher {
   external static Stream<FileSystemEvent> watch(
       String path, int events, bool recursive);
   external static bool get isSupported;
 }