Fix clobber.py to restore args.gn on failure

build/clobber.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """This script provides methods for clobbering build directories."""
 
 import argparse
 import os
 import shutil
@@ skipping 48 matching lines @@
   build_ninja_file = os.path.join(build_dir, 'build.ninja')
   build_commands = extract_gn_build_commands(build_ninja_file)
 
   try:
     gn_args_file = os.path.join(build_dir, 'args.gn')
     with open(gn_args_file, 'r') as f:
       args_contents = f.read()
   except IOError:
     args_contents = ''
 
-  delete_dir(build_dir)
+  e = None
+  try:
+    # delete_dir and os.mkdir() may fail, such as when chrome.exe is running,
+    # and we still want to restore args.gn/build.ninja/build.ninja.d, so catch
+    # the exception and rethrow it later.
+    delete_dir(build_dir)
+    os.mkdir(build_dir)
+  except Exception as e:
+    pass
 
   # Put back the args file (if any).
-  os.mkdir(build_dir)
   if args_contents != '':
     with open(gn_args_file, 'w') as f:
       f.write(args_contents)
 
   # Write the build.ninja file sufficiently to regenerate itself.
   with open(os.path.join(build_dir, 'build.ninja'), 'w') as f:
     if build_commands != '':
       f.write(build_commands)
     else:
       # Couldn't parse the build.ninja file, write a default thing.
       f.write('''rule gn
 command = gn -q gen //out/%s/
 description = Regenerating ninja files
 
 build build.ninja: gn
 generator = 1
 depfile = build.ninja.d
 ''' % (os.path.split(build_dir)[1]))
 
   # Write a .d file for the build which references a nonexistant file. This
   # will make Ninja always mark the build as dirty.
   with open(build_ninja_d_file, 'w') as f:
     f.write('build.ninja: nonexistant_file.gn\n')
 
+  if e:
+    # Rethrow the exception we caught earlier.
+    raise e
 
 def clobber(out_dir):
   """Clobber contents of build directory.
 
   Don't delete the directory itself: some checkouts have the build directory
   mounted."""
   for f in os.listdir(out_dir):
     path = os.path.join(out_dir, f)
     if os.path.isfile(path):
       os.unlink(path)
     elif os.path.isdir(path):
       delete_build_dir(path)
 
 
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('out_dir', help='The output directory to clobber')
   args = parser.parse_args()
   clobber(args.out_dir)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())