copy.py

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#!/usr/bin/env python3
# Copyright 2013 The Flutter Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
 
"""Emulation of `rm -f out && cp -af` in out. This is necessary on Mac in order
to preserve nanoseconds of mtime. See https://fxbug.dev/56376#c5."""
 
import os
import shutil
import sys
 
 
def main():
  if len(sys.argv) != 3:
    print('usage: copy.py source dest', file=sys.stderr)
    return 1
  source = sys.argv[1]
  dest = sys.argv[2]
 
  if os.path.isdir(source):
    print(f'{source} is a directory, tool "copy" does not support directory copies')
    return 1
 
  if os.path.exists(dest):
    if os.path.isdir(dest):
 
      def _on_error(fn, path, dummy_excinfo):
        # The operation failed, possibly because the file is set to
        # read-only. If that's why, make it writable and try the op
        # again.
        if not os.access(path, os.W_OK):
          os.chmod(path, stat.S_IWRITE)
        fn(path)
 
      shutil.rmtree(dest, onerror=_on_error)
    else:
      if not os.access(dest, os.W_OK):
        # Attempt to make the file writable before deleting it.
        os.chmod(dest, stat.S_IWRITE)
      os.unlink(dest)
 
  shutil.copy2(source, dest)
 
 
if __name__ == '__main__':
  main()