pkg_resources.py 文件源码

def _compute_dependencies(self):
        """Recompute this distribution's dependencies."""
        from pip._vendor._markerlib import compile as compile_marker
        dm = self.__dep_map = {None: []}

        reqs = []
        # Including any condition expressions
        for req in self._parsed_pkg_info.get_all('Requires-Dist') or []:
            distvers, mark = self._preparse_requirement(req)
            parsed = next(parse_requirements(distvers))
            parsed.marker_fn = compile_marker(mark)
            reqs.append(parsed)

        def reqs_for_extra(extra):
            for req in reqs:
                if req.marker_fn(override={'extra':extra}):
                    yield req

        common = frozenset(reqs_for_extra(None))
        dm[None].extend(common)

        for extra in self._parsed_pkg_info.get_all('Provides-Extra') or []:
            extra = safe_extra(extra.strip())
            dm[extra] = list(frozenset(reqs_for_extra(extra)) - common)

        return dm