setup_links.py: Use junctions instead of symlinks on Windows.

setup_links.py

 #!/usr/bin/env python
 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 """Setup links to a Chromium checkout for WebRTC.
 
 WebRTC standalone shares a lot of dependencies and build tools with Chromium.
 To do this, many of the paths of a Chromium checkout is emulated by creating
 symlinks to files and directories. This script handles the setup of symlinks to
 achieve this.
-
-It also handles cleanup of the legacy Subversion-based approach that was used
-before Chrome switched over their master repo from Subversion to Git.
 """
 
 
 import ctypes
 import errno
 import logging
 import optparse
 import os
 import shelve
 import shutil
@@ skipping 212 matching lines @@
 
     os.symlink(source_path, os.path.abspath(self._link_path))
     links_db[self._source_path] = self._link_path
 
 
 class LinkError(IOError):
   """Failed to create a link."""
   pass
 
 
-# Handles symlink creation on the different platforms.
+# Use junctions instead of symlinks on the Windows platform.
 if sys.platform.startswith('win'):
   def symlink(source_path, link_path):
-    flag = 1 if os.path.isdir(source_path) else 0
-    if not ctypes.windll.kernel32.CreateSymbolicLinkW(
-        unicode(link_path), unicode(source_path), flag):
-      raise OSError('Failed to create symlink to %s. Notice that only NTFS '
-                    'version 5.0 and up has all the needed APIs for '
-                    'creating symlinks.' % source_path)
+    if os.path.isdir(source_path):
+      subprocess.check_call(['cmd.exe', '/c', 'mklink', '/J', link_path,
+                             source_path])
+    else:
+      # Don't create symlinks to files on Windows, just copy the file instead
+      # (there's no way to create a link without administrator's privileges).
+      shutil.copy(source_path, link_path)
   os.symlink = symlink
 
 
 class WebRTCLinkSetup(object):
   def __init__(self, links_db, force=False, dry_run=False, prompt=False):
     self._force = force
     self._dry_run = dry_run
     self._prompt = prompt
     self._links_db = links_db
 
@@ skipping 31 matching lines @@
       for action in (a for a in actions if a.dangerous):
         action.announce(planning=True)
       print
 
       if not self._force:
         logging.error(textwrap.dedent("""\
         @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
                               A C T I O N     R E Q I R E D
         @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
 
-        Because chromium/src is transitioning to Git (from SVN), we needed to
-        change the way that the WebRTC standalone checkout works. Instead of
-        individually syncing subdirectories of Chromium in SVN, we're now
-        syncing Chromium (and all of its DEPS, as defined by its own DEPS file),
-        into the `chromium/src` directory.
-
-        As such, all Chromium directories which are currently pulled by DEPS are
-        now replaced with a symlink into the full Chromium checkout.
-
-        To avoid disrupting developers, we've chosen to not delete your
-        directories forcibly, in case you have some work in progress in one of
-        them :).
+        Setting up the checkout requires creating symlinks to directories in the
+        Chromium checkout inside chromium/src.
+        To avoid disrupting developers, we've chosen to not delete directories
+        forcibly, in case you have some work in progress in one of them :)
 
         ACTION REQUIRED:
         Before running `gclient sync|runhooks` again, you must run:
         %s%s --force
 
         Which will replace all directories which now must be symlinks, after
         prompting with a summary of the work-to-be-done.
-        """), 'python ' if sys.platform.startswith('win') else '', sys.argv[0])
+        """), 'python ' if sys.platform.startswith('win') else '', __file__)
         sys.exit(1)
       elif self._prompt:
         if not query_yes_no('Would you like to perform the above plan?'):
           sys.exit(1)
 
     for action in actions:
       action.announce(planning=False)
       action.doit(self._links_db)
 
     if not on_bot and self._force:
@@ skipping 17 matching lines @@
                                     shell=True)
             else:
               os.remove(link_path)
           del self._links_db[source]
 
   @staticmethod
   def _ActionForPath(source_path, link_path=None, check_fn=None,
                      check_msg=None):
     """Create zero or more Actions to link to a file or directory.
 
-    This will be a symlink on POSIX platforms. On Windows this requires
-    that NTFS is version 5.0 or higher (Vista or newer).
+    This will be a symlink on POSIX platforms. On Windows it will result in:
+    * a junction for directories
+    * a copied file for single files.
 
     Args:
       source_path: Path relative to the Chromium checkout root.
         For readability, the path may contain slashes, which will
         automatically be converted to the right path delimiter on Windows.
       link_path: The location for the link to create. If omitted it will be the
         same path as source_path.
       check_fn: A function returning true if the type of filesystem object is
         correct for the attempted call. Otherwise an error message with
         check_msg will be printed.
       check_msg: String used to inform the user of an invalid attempt to create
         a file.
     Returns:
       A list of Action objects.
     """
     def fix_separators(path):
       if sys.platform.startswith('win'):
         return path.replace(os.altsep, os.sep)
       else:
         return path
 
     assert check_fn
     assert check_msg
     link_path = link_path or source_path
     link_path = fix_separators(link_path)
 
     source_path = fix_separators(source_path)
     source_path = os.path.join(CHROMIUM_CHECKOUT, source_path)
     if os.path.exists(source_path) and not check_fn:
-      raise LinkError('_LinkChromiumPath can only be used to link to %s: '
-                      'Tried to link to: %s' % (check_msg, source_path))
+      raise LinkError('Can only to link to %s: tried to link to: %s' %
+                      (check_msg, source_path))
 
     if not os.path.exists(source_path):
       logging.debug('Silently ignoring missing source: %s. This is to avoid '
                     'errors on platform-specific dependencies.', source_path)
       return []
 
     actions = []
 
     if os.path.exists(link_path) or os.path.islink(link_path):
       if os.path.islink(link_path):
@@ skipping 62 matching lines @@
   # Work from the root directory of the checkout.
   script_dir = os.path.dirname(os.path.abspath(__file__))
   os.chdir(script_dir)
 
   if sys.platform.startswith('win'):
     def is_admin():
       try:
         return os.getuid() == 0
       except AttributeError:
         return ctypes.windll.shell32.IsUserAnAdmin() != 0
-    if not is_admin():
-      logging.error('On Windows, you now need to have administrator '
-                    'privileges for the shell running %s (or '
-                    '`gclient sync|runhooks`).\nPlease start another command '
-                    'prompt as Administrator and try again.', sys.argv[0])
-      return 1
+    if is_admin():
+      logging.warning('WARNING: On Windows, you no longer need run as '
+                      'administrator. Please run with user account privileges.')
 
   if not os.path.exists(CHROMIUM_CHECKOUT):
     logging.error('Cannot find a Chromium checkout at %s. Did you run "gclient '
                   'sync" before running this script?', CHROMIUM_CHECKOUT)
     return 2
 
   links_database = _initialize_database(LINKS_DB)
   try:
     symlink_creator = WebRTCLinkSetup(links_database, options.force,
                                       options.dry_run, options.prompt)
     symlink_creator.CleanupLinks()
     if not options.clean_only:
       symlink_creator.CreateLinks(on_bot)
   except LinkError as e:
     print >> sys.stderr, e.message
     return 3
   finally:
     links_database.close()
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())