setup_requires="string" not handled by PEP 517 backend

[blueyed]

Related code:

pip/src/pip/_internal/operations/prepare.py

Lines 146 to 149 in e5f4bbb

	with self.req.build_env:
	# We need to have the env active when calling the hook.
	self.req.spin_message = "Getting requirements to build wheel"
	reqs = self.req.pep517_backend.get_requires_for_build_wheel()

reqs will be something like ['wheel', 's', 'e', 't', 'u', 'p', 'm', 'e', 't', 'a'] when using setup_requires='setupmeta'.

• pip version: master (e5f4bbb)
• Python version: 3.7.2
• OS: Arch Linux

Ref: codrsquad/setupmeta#15 (comment)

[blueyed]

setuptools uses yield_lines itself:
https://github.com/pypa/setuptools/blob/cdb5eeae678d8ccc90bf7d4348013a294f11be75/pkg_resources/__init__.py#L2346-L2357
https://github.com/pypa/setuptools/blob/cdb5eeae678d8ccc90bf7d4348013a294f11be75/pkg_resources/__init__.py#L3016-L3022
https://github.com/pypa/setuptools/blob/cdb5eeae678d8ccc90bf7d4348013a294f11be75/setuptools/dist.py#L721-L725

[cjerdonek]

Does this need to be fixed in setuptools rather since the PEP says the return value needs to be a list of strings? https://www.python.org/dev/peps/pep-0517/#get-requires-for-build-wheel

It looks like here is the setuptools code: https://github.com/pypa/setuptools/blob/cdb5eeae678d8ccc90bf7d4348013a294f11be75/setuptools/build_meta.py#L138

[gaborbernat]

Yeah, feels like a setuptools bug to me.

[cjerdonek]

FYI, this has now been fixed in setuptools' master branch.

[chrahunt]

Is there any action needed here?

[blueyed]

Have not checked, closing as per previous from @cjerdonek comment.