pip-compile generates empty requirements.txt

[Burtannia]

I'm trying to use pip-compile to generate requirements.txt from pyproject.toml but for some reason the output from pip-compile doesn't actually contain any dependencies.

Environment Versions

1. OS: macOS Ventura 13.1
2. Python version: 3.11.1
3. pip version: 22.3.1
4. pip-tools version: 6.12.1

Steps to replicate

1. Create a pyproject.toml file containing the following:

[build-system]
requires = ["setuptools<61"]

[project]
name = "python_101"
version = "1.0.0"
description = "Demo Python app"
dependencies = ["pydantic"]

Note that without the setuptools restriction I get the following error when running pip-compile -v ...:

Creating venv isolated environment...
Installing packages in isolated environment... (setuptools >= 40.8.0, wheel)
Getting build dependencies for wheel...
Backend subprocess exited when trying to invoke get_requires_for_build_wheel
Failed to parse /Users/jburton/Projects/python_101/pyproject.toml

2. Run the following command:
   python -m piptools compile --resolver=backtracking --generate-hashes -o requirements.txt pyproject.toml

Expected result

requirements.txt to be populated with dependencies.

Actual result

requirements.txt only contains:

#
# This file is autogenerated by pip-compile with Python 3.11
# by the following command:
#
#    pip-compile --generate-hashes --output-file=requirements.txt --resolver=backtracking pyproject.toml
#

[Burtannia]

@q0w Thanks for the quick response! As mentioned in "step 1", if I use setuptools>61 or remove the restriction and allow the default to be used then I get the following error:

Backend subprocess exited when trying to invoke get_requires_for_build_wheel
Failed to parse /Users/jburton/Projects/python_101/pyproject.toml

[q0w]

@Burtannia oh I see... Could you apply this patch #1711 (comment) and show the error. I can't reproduce

[Burtannia]

@q0w Aha! It seemed to be getting confused when finding the package directory. I had a top level directory called proto containing only a .proto file which seemed to be enough for it to not find the actual package directory. Upon adding the following to my pyproject.toml everything worked:

[tool.setuptools]
packages = ["python_101"]

I've made a PR to add some debugging tips and a note about setuptools to the README #1797

Thanks for the help!