utils/bazel/overlay_directories.py

   1 #!/bin/python3
   2
   3 # This file is licensed under the Apache License v2.0 with LLVM Exceptions.
   4 # See https://llvm.org/LICENSE.txt for license information.
   5 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 """Overlays two directories into a target directory using symlinks.
   7
   8 Tries to minimize the number of symlinks created (that is, does not symlink
   9 every single file). Symlinks every file in the overlay directory. Only symlinks
  10 individual files in the source directory if their parent directory is also
  11 contained in the overlay directory tree.
  12 """
  13
  14 import argparse
  15 import errno
  16 import os
  17 import sys
  18
  19
  20 def _check_python_version():
  21     if sys.version_info[0] < 3:
  22         raise RuntimeError(
  23             "Must be invoked with a python 3 interpreter but was %s" % sys.executable
  24         )
  25
  26
  27 def _check_dir_exists(path):
  28     if not os.path.isdir(path):
  29         raise OSError(errno.ENOENT, os.strerror(errno.ENOENT), path)
  30
  31
  32 def parse_arguments():
  33     parser = argparse.ArgumentParser(
  34         description="""
  35     Overlays two directories into a target directory using symlinks.
  36
  37     Tries to minimize the number of symlinks created (that is, does not symlink
  38     every single file). Symlinks every file in the overlay directory. Only
  39     symlinks individual files in the source directory if their parent directory
  40     is also contained in the overlay directory tree.
  41     """
  42     )
  43     parser.add_argument(
  44         "--src",
  45         required=True,
  46         help="Directory that contains most of the content to symlink.",
  47     )
  48     parser.add_argument(
  49         "--overlay",
  50         required=True,
  51         help="Directory to overlay on top of the source directory.",
  52     )
  53     parser.add_argument(
  54         "--target",
  55         required=True,
  56         help="Directory in which to place the fused symlink directories.",
  57     )
  58
  59     args = parser.parse_args()
  60
  61     _check_dir_exists(args.target)
  62     _check_dir_exists(args.overlay)
  63     _check_dir_exists(args.src)
  64
  65     return args
  66
  67
  68 def _symlink_abs(from_path, to_path):
  69     os.symlink(os.path.abspath(from_path), os.path.abspath(to_path))
  70
  71
  72 def main(args):
  73     for root, dirs, files in os.walk(args.overlay):
  74         # We could do something more intelligent here and only symlink individual
  75         # files if the directory is present in both overlay and src. This could also
  76         # be generalized to an arbitrary number of directories without any
  77         # "src/overlay" distinction. In the current use case we only have two and
  78         # the overlay directory is always small, so putting that off for now.
  79         rel_root = os.path.relpath(root, start=args.overlay)
  80         if rel_root != ".":
  81             os.mkdir(os.path.join(args.target, rel_root))
  82
  83         for file in files:
  84             relpath = os.path.join(rel_root, file)
  85             _symlink_abs(
  86                 os.path.join(args.overlay, relpath), os.path.join(args.target, relpath)
  87             )
  88
  89         for src_entry in os.listdir(os.path.join(args.src, rel_root)):
  90             if src_entry not in dirs:
  91                 relpath = os.path.join(rel_root, src_entry)
  92                 _symlink_abs(
  93                     os.path.join(args.src, relpath), os.path.join(args.target, relpath)
  94                 )
  95
  96
  97 if __name__ == "__main__":
  98     _check_python_version()
  99     main(parse_arguments())