Generate depfile for python scripts

deptrace.py

#! /usr/bin/python3
# coding: utf-8

# Author: Marc-André Lureau <marcandre.lureau@redhat.com>

import sys
import os
import atexit
from importlib import invalidate_caches
from importlib.machinery import FileFinder, SourceFileLoader

class DepLoader(SourceFileLoader):
    loaded = set()

    def get_code(self, fullname):
        self.loaded.add(self.get_filename(fullname))
        return super().get_code(fullname)


def exit_handler(opts):
    if not opts.depfile:
        opts.depfile = os.path.basename(opts.filename) + '.d'

    with open(opts.depfile, 'w') as out:
        print('%s: %s' % (opts.filename, ' '.join(DepLoader.loaded)), file=out)


def main():
    import argparse

    parser = argparse.ArgumentParser(
        description='Generate depfile for python scripts')

    parser.add_argument('-d', '--depfile',
            help='depfile filename location (default to filename.d)')
    parser.add_argument('filename', nargs='?',
            help='file to run as main program')
    parser.add_argument('arguments', nargs=argparse.REMAINDER,
            help='arguments to the program')

    opts = parser.parse_args()

    if opts.filename is None:
        parser.error('filename is missing: required with the main options')

    sys.argv = [opts.filename, *opts.arguments]
    sys.path[0] = os.path.dirname(opts.filename)

    loader_details = DepLoader, [".py"]
    # insert the path hook ahead of other path hooks
    sys.path_hooks.insert(0, FileFinder.path_hook(loader_details))
    # clear any loaders that might already be in use by the FileFinder
    sys.path_importer_cache.clear()
    invalidate_caches()

    atexit.register(exit_handler, opts)

    try:
        with open(opts.filename) as fp:
            code = compile(fp.read(), opts.filename, 'exec')
        # try to emulate __main__ namespace as much as possible
        globs = {
            '__file__': opts.filename,
            '__name__': '__main__',
            '__package__': None,
            '__cached__': None,
        }
        exec(code, globs, globs)
    except OSError as err:
        sys.exit("Cannot run file %r because: %s" % (sys.argv[0], err))
    except SystemExit:
        pass


if __name__=='__main__':
    main()