dart:io | Add FileSystemEntity.parent, make File.directory call it.

sdk/lib/io/file_system_entity.dart

Index: sdk/lib/io/file_system_entity.dart
diff --git a/sdk/lib/io/file_system_entity.dart b/sdk/lib/io/file_system_entity.dart
index fdeb923c6de41dc31715e1dc13192afcd6546ee2..b2b315f97e337cf38873747f45e2dccc3ae58a10 100644
--- a/sdk/lib/io/file_system_entity.dart
+++ b/sdk/lib/io/file_system_entity.dart
@@ -530,6 +530,42 @@ abstract class FileSystemEntity {
   external static _identical(String path1, String path2);
   external static _resolveSymbolicLinks(String path);
 
+  /**
+   * The directory containing [this].  If [this] is a root
+   * directory, returns [this].
+   */
+  Directory get parent {

[Søren Gjesse, 2013/10/04 12:20:16]

How about

return new Directory(new Uri.file(path).resolve('..').toFilePath());

[Bill Hesse, 2013/10/04 12:41:06]

This will not give the desired result, since it will remove all '..' and '.'
segments, and it will do different things depending on whether there are
trailing slashes.

+    if (Platform.isWindows) {
+      int rootEnd = -1;
+      if (path.startsWith(_absoluteWindowsPathPattern)) {
+        // Root ends at first / or \ after the first two characters.
+        rootEnd = path.indexOf(new RegExp(r'[/\\]'), 2);
+        if (rootEnd == -1) return new Directory(path);
+      }
+      // Ignore trailing slashes - find a slash followed by a non-slash.
+      int pos = path.lastIndexOf(new RegExp(r'[/\\][^/\\]'));
+      if (pos <= rootEnd) {
+        if (rootEnd == -1) {
+          return new Directory('.');
+        } else {
+          return new Directory(path.substring(0, rootEnd + 1));
+        }
+      }
+      while (pos > rootEnd + 1 &&
+             (path[pos - 1] == '\\' || path[pos - 1] == '/')) {
+        pos--;
+      }
+      return new Directory(path.substring(0, pos));
+    } else {
+      // Ignore trailing slashes - find a slash followed by a non-slash.
+      int pos = path.lastIndexOf(new RegExp(r'/[^/]'));
+      if (pos < 0) return new Directory('.');
+      while (pos > 0 && path[pos - 1] == '/') --pos;
+      if (pos == 0) return new Directory('/');
+      return new Directory(path.substring(0, pos));
+    }
+  }
+
   static int _getTypeSync(String path, bool followLinks) {
     var result = _getType(path, followLinks);
     _throwIfError(result, 'Error getting type of FileSystemEntity');
@@ -537,12 +573,13 @@ abstract class FileSystemEntity {
   }
 
   static Future<int> _getTypeAsync(String path, bool followLinks) {
-    return _IOService.dispatch(_FILE_TYPE, [path, followLinks]).then((response) {
-      if (_isErrorResponse(response)) {
-        throw _exceptionFromResponse(response, "Error getting type", path);
-      }
-      return response;
-    });
+    return _IOService.dispatch(_FILE_TYPE, [path, followLinks])
+      .then((response) {
+        if (_isErrorResponse(response)) {
+          throw _exceptionFromResponse(response, "Error getting type", path);
+        }
+        return response;
+      });
   }
 
   static _throwIfError(Object result, String msg, [String path]) {