matrix environments with parent environment with different python version raise an error

[juftin]

This can be problematic in CI/CD where you run hatch run +py={{ matrix.python }} matrix:cov and have hatch.python set to a differing version than your current matrix version

[tool.hatch.envs.default]
pip-compile-constraint = "default"
type = "pip-compile"
python = "3.11"

[tool.hatch.envs.test]
dependencies = [
  "pytest",
  "pytest-cov"
]

[tool.hatch.envs.test.scripts]
cov = [
  "pytest --cov-config=pyproject.toml --cov {args:tests}"
]

[tool.hatch.envs.matrix]
template = "test"

[[tool.hatch.envs.matrix.matrix]]
python = ["3.8", "3.9", "3.10", "3.11", "3.12"]

In the above example you must have the 3.11 environment available to use pip-compile environments from a matrix because default is a constraint environment

AttributeError: 'NoneType' object has no attribute 'executable'

https://github.com/juftin/hatch-pip-compile/actions/runs/7117731072/job/19379122673?pr=28

See how this is handled here:

hatch-pip-compile/.github/workflows/tests.yaml

Lines 41 to 49 in 238fd44

	- name: Set up Python Environment ${{ matrix.python }}
	uses: actions/setup-python@v4
	with:
	python-version: ${{ matrix.python }}
	- name: Install Default Python
	if: matrix.python != '3.11'
	uses: actions/setup-python@v4
	with:
	python-version: "3.11"

IMO this isn't a bug - but this should probably be documented

[juftin]

The way that it's handled in this repo means we generate a lockfile for each Python version - if you wanted one lockfile for all python versions you could handle it like this and forget the hatch matrix entirely:

[tool.hatch.envs.default]
type = "pip-compile"
python = "3.11"

[tool.hatch.envs.test]
template = "test"
dependencies = [
  "pytest",
  "pytest-cov"
]
type = "pip-compile"
pip-compile-constraint = "default"

[tool.hatch.envs.test.scripts]
cov = [
  "pytest --cov-config=pyproject.toml --cov {args:tests}"
]