Function safe_copy

pex/common.py:178–228

(source, dest, overwrite=False)

def safe_copy(source, dest, overwrite=False):
    # type: (Text, Text, bool) -> None
    def do_copy():
        # type: () -> None
        temp_dest = dest + uuid4().hex
        shutil.copy(source, temp_dest)
        safe_rename(temp_dest, dest)

    # If the platform supports hard-linking, use that and fall back to copying.
    # Windows does not support hard-linking.
    if hasattr(os, "link"):
        try:
            safe_link(source, dest)
        except OSError as e:
            if e.errno == errno.EEXIST:
                # File already exists.  If overwrite=True, write otherwise skip.
                if overwrite:
                    do_copy()
            elif e.errno in (errno.EPERM, errno.EXDEV):
                # For a hard link across devices issue, fall back on copying.
                #
                # For a permission issue, the cause could be one of:
                # 1. We can't read source.
                # 2. We can't write dest.
                # 3. We don't own source but can read it.
                # Although we can't do anything about cases 1 and 2, case 3 is due to
                # `protected_hardlinks` (see: https://www.kernel.org/doc/Documentation/sysctl/fs.txt) and
                # we can fall back to copying in that case.
                #
                # See also https://github.com/pex-tool/pex/issues/850 where this was discovered.
                do_copy()
            else:
                raise OSError(
                    e.errno,
                    "Failed to link {src} -> {dst}: {strerror}\n"
                    "{process_diagnostic}\n"
                    "{src_diagnostic}\n"
                    "{dst_diagnostic}".format(
                        src=source,
                        dst=dest,
                        strerror=e.strerror,
                        process_diagnostic=_process_diagnostic(),
                        src_diagnostic=_path_diagnostic(source),
                        dst_diagnostic=_path_diagnostic(os.path.dirname(dest)),
                    ),
                )
    elif os.path.exists(dest):
        if overwrite:
            do_copy()
    else:
        do_copy()


# See http://stackoverflow.com/questions/2572172/referencing-other-modules-in-atexit