Publish `Requires-Dist` for source distributions when using `setup.cfg`?

[di]

Consider the following example:

setup.py:

from setuptools import setup

setup()

setup.cfg:

[metadata]
name = setup-cfg-example
version = 0.0.0
[options]
install_requires =
    foobar

When building a built distribution, the following metadata is produced:

Metadata-Version: 2.1
Name: setup-cfg-example
Version: 0.0.0
Summary: UNKNOWN
Home-page: UNKNOWN
Author: UNKNOWN
Author-email: UNKNOWN
License: UNKNOWN
Platform: UNKNOWN
Requires-Dist: foobar

UNKNOWN

However for the same source distribution:

Metadata-Version: 1.0
Name: setup-cfg-example
Version: 0.0.0
Summary: UNKNOWN
Home-page: UNKNOWN
Author: UNKNOWN
Author-email: UNKNOWN
License: UNKNOWN
Description: UNKNOWN
Platform: UNKNOWN

In this case, where install_requires is set in setup.cfg and is completely deterministic, should setuptools include Requires-Dist in the metadata for the source distribution?

[jaraco]

Yes, that seems reasonable.

[tacaswell]

Is there any practical consequence on requires_dist being missing?

---

There only being one (immutable) version of this at the top-level also seems problematic if different wheels (for different Python or platform) have different dependencies (this is very common with packages that depend on numpy).

[jelmer]

Apparently one of the consequences is that this field allows package managers to figure out dependencies before they have to go and download the wheel.

[abravalheri]

This requires a "modernization" on how setuptools builds sdist, specifically, we need to make the PKG-INFO file properly aligned with the core metadata specifications.

If anyone would like to contribute, help implementing would be very appreciated.

Some time ago I started to contribute to pypa/packaging#498, but it seems that there is a lot to be discussed there and the maintainers might prefer a different path (so we might start with the implementation inside of setuptools first).

[yosefm]

I'd like to help, but I need some direction. Where would you make the change in setuptools? I looked at pypa/packaging#498 but didn't get how it's meant to be used.