Modify _reqs.py to prefer prefer packaging instead of pkg_resources

setuptools/_reqs.py

@@ -1,9 +1,13 @@
+from typing import Callable, Iterable, Iterator, TypeVar, Union, overload
+
 import setuptools.extern.jaraco.text as text
+from setuptools.extern.packaging.requirements import Requirement
 
-from pkg_resources import Requirement
+_T = TypeVar("_T")
+_StrOrIter = Union[str, Iterable[str]]
 
 
-def parse_strings(strs):
+def parse_strings(strs: _StrOrIter) -> Iterator[str]:
     """
     Yield requirement strings for each specification in `strs`.
 
@@ -12,8 +16,18 @@ def parse_strings(strs):
     return text.join_continuation(map(text.drop_comment, text.yield_lines(strs)))
 
 
-def parse(strs):
+@overload
+def parse(strs: _StrOrIter) -> Iterator[Requirement]:
+    ...
+
+
+@overload
+def parse(strs: _StrOrIter, parser: Callable[[str], _T]) -> Iterator[_T]:
+    ...
+
+
+def parse(strs, parser=Requirement):
     """
-    Deprecated drop-in replacement for pkg_resources.parse_requirements.
+    Replacement for ``pkg_resources.parse_requirements`` that uses ``packaging``.
     """
-    return map(Requirement, parse_strings(strs))
+    return map(parser, parse_strings(strs))