Run tests for multiple python versions

[iaptsiauri]

Hey everyone, we are using pants build system to manage python monorepo which consists of multiple different packages which we provide as a standalone dependency or bundled in a framework. We want to run the tests for multiple diffrenet python versions. Doing this in tox is quite straigtforward by eding pythong version to envlist. Unfortunatelly I wasn't able to find the same option with pants test goal. I wonder if it is possible or some other tweaking should be done

[kaos]

The way you can do this with pants is to parametrize the tests over the desired set of interpreter constraints you want to use.

python_test(
    name="tests",
    source="tests.py",
    interpreter_constraints=parametrize(py2=["==2.7.*"], py3=[">=3.6"]),
)

https://www.pantsbuild.org/docs/python-interpreter-compatibility#using-multiple-python-versions-in-the-same-project
https://www.pantsbuild.org/docs/targets#parametrizing-targets

[benjyw]

Yep. Then you can use a full address like path/to:tests@interpreter_constraints=py2 selector to run over just one interpreter.

Unfortunately ::@interpreter_constraints=py2 doesn't work (yet?)

[jsirois]

Yeah, that's a bit of a problem coming from tox.

[jsirois]

If Pants were dogfooding this from the get go that likely would've shaken a bit out. Right now it uses bespoke scripts and env vars along with CPython>=3.7,<3.10. It probably should just be using 3 resolves. One each for CPython==3.7.*, CPython==3.8.* and CPython==3.9.*.

[iaptsiauri]

Yeah I had the same impression initially, that 3 resolvers would have been used. Anyways thanks for you help, I might come back with some more questions later :)

[stuhood]

#17856 is the ticket intended to cover this filtering usecase, although it wasn't in the title (fixed now).