Add ability to specify which Python versions to run with from the command line.

[theacodes]

Context: https://github.com/theacodes/nox/pull/94/files/ad56baafab381ef967f504b1c2d9dc30d61bc96e#r205984653

[stsewd]

What about implicit specifying the python version on the session name? Something like:

@nox.session(python=['3.5', '3.6'])
def test():
    ...

$ nox -s test-3.7
nox> Warning: running session with custom interpreter
...

[theacodes]

I think that's a separate use case, but a useful one. Wanna file a separate bug for it?

[stsewd]

So, this issue is about something like filtering by python interpreter?

[stsewd]

I opened #158

[jarus]

This would be a super helpful enhancement and would make nox even more useful, especially in situations where the developer would like to run a session(s) with one or multiple selected python version(s).

Do you have already a favourite solution for this problem which you would like to see in nox?

As a short term solution, I think it would be sufficient to add the python version in a normalized form (3.7 => py37) to the keyword list beside the SessionRunner.signature so that nox -k py37 only select sessions with the python 3.7 interpreter. Is that something you would welcome? If yes, I can create a pull request.

In general, I like nox's and pytest's intention to reuse an already known and established syntax like Python's logical operators for selecting sessions or tests but the current simple implementations with Python eval function also come with some disadvantages. For example it blocks the usage of keywords that don't follow the Python variable name rule like 3.7, test-3.7 or from. Therefore it is maybe a good idea to think about replacing eval with an own matcher with a more flexible syntax.

[theacodes]

@jarus, that sounds great - do you want to create a separate issue for that so we can track it? I'm more than happy to see a PR for that.

[theacodes]

This issue is actually a great first issue. It involves:

1. Adding a new command-line parameter --python (or similar)
2. Updating manifest's filtering to filter based on the --python parameter.

[vikrambhat11]

Hi @theacodes ,

I would like to take a look at this issue if no one is already working on it.
Just had some questions before I start this.

Should the --python parameter work only with a specified task? My question is, will this be a supported case nox --python 3.7 on the command line? Or should it always be nox --session s1 --python 3.7

I have a couple of ideas to work on this depending on what we decide on this. Would love to discuss this.

[theacodes]

It should work as an additional filter to the manifest. `--session` filters the manifest by name, `--keyword` filters the manifest through pattern matching, and `--python` should filter the manifest by python version.

…

On Tue, Aug 27, 2019 at 10:34 PM Vikram Bhat ***@***.***> wrote: Hi @theacodes <https://github.com/theacodes> , I would like to take a look at this issue if no one is already working on it. Just had some questions before I start this. Should the --python parameter work only with a specified task? My question is, will this be a supported case nox --python 3.7 on the command line? Or should it always be nox --session s1 --python 3.7 I have a couple of ideas to work on this depending on what we decide on this. Would love to discuss this. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#95>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAB5I432TE7BDYGG3GEBI6TQGYE5BANCNFSM4FMWKUSA> .

[maciej-lech]

As @vikrambhat11 has not been prepared a PR for this one, I'd like to propose my implementation as it would be a more convenient way for filtering by python interpreter versions comparing to using keywords.

[pradyunsg]

This can be closed, given #304 is merged?

[theacodes]

Yup, thanks.