implement unlink on Windows

client/utils/fs.py

 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Wraps os, os.path and shutil functions to work around MAX_PATH on Windows."""
 
 import __builtin__
 import inspect
 import os
 import shutil
 import sys
 
 
 if sys.platform == 'win32':
 
 
   import ctypes
-  GetFileAttributesW = ctypes.windll.kernel32.GetFileAttributesW
-  GetFileAttributesW.argtypes = (ctypes.c_wchar_p,)
-  GetFileAttributesW.restype = ctypes.c_uint
   CreateSymbolicLinkW = ctypes.windll.kernel32.CreateSymbolicLinkW
   CreateSymbolicLinkW.argtypes = (
       ctypes.c_wchar_p, ctypes.c_wchar_p, ctypes.c_uint32)
   CreateSymbolicLinkW.restype = ctypes.c_ubyte
+  DeleteFile = ctypes.windll.kernel32.DeleteFileW
+  DeleteFile.argtypes = (ctypes.c_wchar_p,)
+  DeleteFile.restype = ctypes.c_bool
+  GetFileAttributesW = ctypes.windll.kernel32.GetFileAttributesW
+  GetFileAttributesW.argtypes = (ctypes.c_wchar_p,)
+  GetFileAttributesW.restype = ctypes.c_uint
+  RemoveDirectory = ctypes.windll.kernel32.RemoveDirectoryW
+  RemoveDirectory.argtypes = (ctypes.c_wchar_p,)
+  RemoveDirectory.restype = ctypes.c_bool
 
 
   def extend(path):
     """Adds '\\\\?\\' when given an absolute path so the MAX_PATH (260) limit is
     not enforced.
     """
     assert os.path.isabs(path), path
     assert isinstance(path, unicode), path
     prefix = u'\\\\?\\'
     return path if path.startswith(prefix) else prefix + path
@@ skipping 33 matching lines @@
     Privilege constants:
       https://msdn.microsoft.com/library/windows/desktop/bb530716.aspx
     """
     # TODO(maruel): This forces always creating absolute path symlinks.
     source = extend(source)
     flags = 1 if os.path.isdir(source) else 0
     if not CreateSymbolicLinkW(extend(link_name), source, flags):
       raise WindowsError()  # pylint: disable=undefined-variable
 
 
+  def unlink(path):
+    """Removes a symlink on Windows 7 and later.
+
+    Does not delete the link source.
+
+    If path is not a link, but a non-empty directory, will fail with a
+    WindowsError.
+
+    Useful material:
+    CreateSymbolicLinkW:
+      https://msdn.microsoft.com/library/windows/desktop/aa363866.aspx
+    DeleteFileW:
+      https://msdn.microsoft.com/en-us/library/windows/desktop/aa363915(v=vs.85).aspx
+    RemoveDirectoryW:
+      https://msdn.microsoft.com/en-us/library/windows/desktop/aa365488(v=vs.85).aspx
+    """
+    path = extend(path)
+    if os.path.isdir(path):
+      if not RemoveDirectory(path):
+        # pylint: disable=undefined-variable
+        raise WindowsError('could not remove directory "%s"' % path)
+    else:
+      if not DeleteFile(path):
+        # pylint: disable=undefined-variable
+        raise WindowsError('could not delete file "%s"' % path)
+
+
   def walk(top, *args, **kwargs):
     return os.walk(extend(top), *args, **kwargs)
 
 
 else:
 
 
   def extend(path):
     """Convert the path back to utf-8.
 
@@ skipping 12 matching lines @@
     return path.decode('utf-8')
 
 
   def islink(path):
     return os.path.islink(extend(path))
 
 
   def symlink(source, link_name):
     return os.symlink(source, extend(link_name))
 
+  def unlink(path):
+    return os.unlink(extend(path))
 
   def walk(top, *args, **kwargs):
     for root, dirs, files in os.walk(extend(top), *args, **kwargs):
       yield trim(root), dirs, files
 
 
 ## builtin
 
 
 def open(path, *args, **kwargs):  # pylint: disable=redefined-builtin
@@ skipping 50 matching lines @@
 for _fn in _os_fns:
   if hasattr(os, _fn):
     sys.modules[__name__].__dict__.setdefault(
         _fn, _get_lambda(getattr(os, _fn)))
 
 
 for _fn in _os_path_fns:
   if hasattr(os.path, _fn):
     sys.modules[__name__].__dict__.setdefault(
         _fn, _get_lambda(getattr(os.path, _fn)))