add support for RustPython under posix

[elmjag]

Adds support for creating virtual environment using RustPython interpreter:
https://github.com/RustPython/RustPython

Without this 'custom' RustPython creator virtualenv fails, when specifying rustpython binary with --python argument. For example:

$ virtualenv --with-traceback --python <...>/target/release/rustpython foo

Traceback (most recent call last):
  File "/opt/mamba/envs/virtenvbug/bin/virtualenv", line 7, in <module>
    sys.exit(run_with_catch())
             ~~~~~~~~~~~~~~^^
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/__main__.py", line 68, in run_with_catch
    run(args, options, env)
    ~~~^^^^^^^^^^^^^^^^^^^^
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/__main__.py", line 21, in run
    session = cli_run(args, options, env)
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/run/__init__.py", line 31, in cli_run
    of_session = session_via_cli(args, options, setup_logging, env)
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/run/__init__.py", line 52, in session_via_cli
    creator, seeder, activators = tuple(e.create(options) for e in elements)  # create types
                                  ^^^^^
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/run/__init__.py", line 52, in <genexpr>
    creator, seeder, activators = tuple(e.create(options) for e in elements)  # create types
                                        ~~~~~~~~^^^^^^^^^
  File "/opt/mamba/envs/virtenvbug/lib/python3.14/site-packages/virtualenv/run/plugin/creators.py", line 84, in create
    options.describe = self.describe(options, self.interpreter)
                       ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not callable

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gaborbernat]

Tests?

[elmjag]

Tests?

I have added some tests:
https://github.com/pypa/virtualenv/pull/3010/changes#diff-c6bbc192a20cf820e49159ddb97e90abc2c17f5259d9387358af4c4807ce0279

[gaborbernat]

Tests?

I have added some tests: #3010 (changes)

This is not sufficient, you'll need to do what we do for PyPy and add it to the CI as a matrix, fix the errors and then would be ready.

[elmjag]

This is not sufficient, you'll need to do what we do for PyPy and add it to the CI as a matrix, fix the errors and then would be ready.

I'm trying to wrap my head around how the virtualenv CI tests work.

As far as I understand, the python version under test is installed with actions/setup-python GitHub action. Then it's picked up by tox, when it is running the tests.

In order to add RustPython to the matrix, I see two options:

• add support to actions/setup-python so it can install RustPython
• add special case for RustPython, where it's installed with some different method

Is my understanding correct?

[gaborbernat]

Yes

[gaborbernat]

Yes