[BUG] setting install_requires=[] disables dynamic requires-dist

[lmondada]

setuptools version

setuptools==80.9

Python version

Python 3.12 (should not matter)

OS

n/a

Additional environment information

No response

Description

When passing an empty install_requires=[] argument to setup(), the generated PKG-INFO does not contain the line

Dynamic: requires-dist

even though project.dynamic = ["dependencies"] is set in pyproject.toml.

Why this edge case?

The cudaq project publishes multiple packages wheels for multiple supported versions of CUDA. We then have a metapackage that is sdist only that finds the installed CUDA version on the user's system at install time and sets its dependency dynamically accordingly.

To achieve this, the sdist package initially declares an empty dependency list.

Expected behavior

The file PKG-INFO generated by python -m build should contain a line

Dynamic: requires-dist

How to Reproduce

1. create an empty package with project.dynamic = ["dependencies"] set in pyproject.toml
2. set the build backend to setuptools.build_meta and create a setup.py file with setup(install_requires=[])
3. run python -m build
4. cd dist && tar xvf package-name-version.tar.gz && cat package-name-version/PKG-INFO | grep Dynamic

Output

The fourth step outputs nothing. It should output Dynamic: requires-dist

[lmondada]

relates to astral-sh/uv#12759 and NVIDIA/cuda-quantum#3616

[abravalheri]

Hi @lmondada thanks for the report.

Just one comment the: dynamic field in pyproject.toml is not the same thing as the Dynamic field in the core metadata... They are associated with similar concepts but they have 2 independent behaviours. In fact, you can have Dynamic core metadata without even having to specify pyproject.toml. And you can have dynamic in pyproject.toml without having Dynamic in the core metadata.

That said, this undesired behaviour probably emerges from

setuptools/setuptools/_core_metadata.py

Line 215 in 9c4d383

if (val := getattr(self, attr, None)) and not is_static(val):

, i.e. because the value set for install_requires is a false-y value, it does not get evaluated according to staticness.

Sounds a bit challenging considering backwards compatibility and the default values inherited by distutils... I need to think about it.

I will add the label help wanted in the case any member of the community also wants to have a look on this (it will probably take me a while to find the time). If anyone is interested in submitting a PR, it would be important to have regression tests to ensure backwards compatibility.

Another, maybe "easier" way out could also be some form of explicit marker for dynamic values, roughly something like setuptools.setup(install_requires=setuptools.DYNAMIC_PLACEHOLDER), so that we can circumvent the complications... (and/or automatically set this dynamic placeholder when evaluating dynamic from pyproject.toml??)

[abravalheri]

By the way this is a possible minimum reproducible example as required by the issue form, as a "copy/paste-able script":

# docker run --rm -it python:3.12-bookworm /bin/bash

mkdir /tmp/project

cd /tmp/project

cat <<EOF > pyproject.toml
[build-system]
requires = ["setuptools==80.9.0"]
build-backend = "setuptools.build_meta"

[project]
name = "project"
version = "0.42"
dynamic = ["dependencies"]
EOF

cat <<EOF > setup.py
from setuptools import setup

setup(
  install_requires=[]
)
EOF

python -m venv .venv
.venv/bin/python -m pip install -U "build==1.3.0"
.venv/bin/python -m build .

tar xzfO dist/project-0.42.tar.gz  project-0.42/PKG-INFO
# Metadata-Version: 2.4
# Name: project
# Version: 0.42