Function RelativePath

tools/gyp/pylib/gyp/common.py:135–174

(path, relative_to, follow_path_symlink=True)

@memoize
def RelativePath(path, relative_to, follow_path_symlink=True):
    # Assuming both |path| and |relative_to| are relative to the current
    # directory, returns a relative path that identifies path relative to
    # relative_to.
    # If |follow_symlink_path| is true (default) and |path| is a symlink, then
    # this method returns a path to the real file represented by |path|. If it is
    # false, this method returns a path to the symlink. If |path| is not a
    # symlink, this option has no effect.

    # Convert to normalized (and therefore absolute paths).
    path = os.path.realpath(path) if follow_path_symlink else os.path.abspath(path)
    relative_to = os.path.realpath(relative_to)

    # On Windows, we can't create a relative path to a different drive, so just
    # use the absolute path.
    if sys.platform == "win32" and (
        os.path.splitdrive(path)[0].lower()
        != os.path.splitdrive(relative_to)[0].lower()
    ):
        return path

    # Split the paths into components.
    path_split = path.split(os.path.sep)
    relative_to_split = relative_to.split(os.path.sep)

    # Determine how much of the prefix the two paths share.
    prefix_len = len(os.path.commonprefix([path_split, relative_to_split]))

    # Put enough ".." components to back up out of relative_to to the common
    # prefix, and then append the part of path_split after the common prefix.
    relative_split = [os.path.pardir] * (
        len(relative_to_split) - prefix_len
    ) + path_split[prefix_len:]

    if len(relative_split) == 0:
        # The paths were the same.
        return ""

    # Turn it back into a string and we're done.
    return os.path.join(*relative_split)


@memoize