Recommit add FileSystemEntity.resolveSymbolicLinks

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 ab2b7d30c61f630e84bf8419d31195e999924123..10d632bb15940232edd5e1d2a87dcfd9410fb893 100644
--- a/sdk/lib/io/file_system_entity.dart
+++ b/sdk/lib/io/file_system_entity.dart
@@ -221,6 +221,68 @@ abstract class FileSystemEntity {
   FileSystemEntity renameSync(String newPath);
 
   /**
+   * Resolves the path of a file system object relative to the
+   * current working directory, resolving all symbolic links on
+   * the path and resolving all '..' and '.' path segments.
+   * [resolveSymbolicLinks] returns a [:Future<String>:]
+   *
+   * [resolveSymbolicLinks] uses the operating system's native filesystem api
+   * to resolve the path, using the realpath function on linux and
+   * Mac OS, and the GetFinalPathNameByHandle function on Windows.
+   * If the path does not point to an existing file system object,
+   * [resolveSymbolicLinks] completes the returned Future with an FileException.
+   *
+   * On Windows, symbolic links are resolved to their target before applying
+   * a '..' that follows, and on other platforms, the '..' is applied to the
+   * symbolic link without resolving it.  The second behavior can be emulated
+   * on Windows by processing any '..' segments before calling
+   * [resolveSymbolicLinks].  One way of doing this is with the URI class:
+   * [:new Uri.parse('.').resolveUri(new Uri.file(input)).toFilePath();],
+   * since [resolve] removes '..' segments.
+   */
+  Future<String> resolveSymbolicLinks() {
+    // Get a new file service port for each request.  We could also cache one.
+    var service = _FileUtils._newServicePort();
+    List request = new List(2);
+    request[0] = _RESOLVE_SYMBOLIC_LINKS_REQUEST;
+    request[1] = path;
+    return service.call(request).then((response) {
+      if (_isErrorResponse(response)) {
+        throw _exceptionFromResponse(response,
+                                     "Cannot resolve symbolic links",
+                                     path);
+      }
+      return response;
+    });
+  }
+
+  /**
+   * Resolves the path of a file system object relative to the
+   * current working directory, resolving all symbolic links on
+   * the path and resolving all '..' and '.' path segments.
+   *
+   * [resolveSymbolicLinksSync] uses the operating system's native
+   * filesystem api to resolve the path, using the realpath function
+   * on linux and Mac OS, and the GetFinalPathNameByHandle function on Windows.
+   * If the path does not point to an existing file system object,
+   * [resolveSymbolicLinksSync] throws a FileException.
+   *
+   * On Windows, symbolic links are resolved to their target before applying
+   * a '..' that follows, and on other platforms, the '..' is applied to the
+   * symbolic link without resolving it.  The second behavior can be emulated
+   * on Windows by processing any '..' segments before calling
+   * [resolveSymbolicLinks].  One way of doing this is with the URI class:
+   * [:new Uri.parse('.').resolveUri(new Uri.file(input)).toFilePath();],
+   * since [resolve] removes '..' segments.
+   */
+  String resolveSymbolicLinksSync() {
+    var result = _resolveSymbolicLinks(path);
+    _throwIfError(result, "Cannot resolve symbolic links", path);
+    return result;
+  }
+
+
+  /**
    * Calls the operating system's stat() function on the [path] of this
    * [FileSystemEntity].  Identical to [:FileStat.stat(this.path):].
    *
@@ -316,7 +378,7 @@ abstract class FileSystemEntity {
   void _deleteSync({recursive: false});
 
   /**
-   * Synchronously checks whether two paths refer to the same object in the
+   * Checks whether two paths refer to the same object in the
    * file system. Returns a [:Future<bool>:] that completes with the result.
    *
    * Comparing a link to its target returns false, as does comparing two links
@@ -481,6 +543,7 @@ abstract class FileSystemEntity {
 
   external static _getType(String path, bool followLinks);
   external static _identical(String path1, String path2);
+  external static _resolveSymbolicLinks(String path);
 
   static int _getTypeSync(String path, bool followLinks) {
     var result = _getType(path, followLinks);