Add -prof tox environment

[ShadowJonathan]

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
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Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

[ShadowJonathan]

(I think it would also be handy to add this to CONTRIBUTING.md, but i have no idea how to go about that when #9281 is also going on)

[richvdh]

I'm not really convinced this is worthwhile: it's just extra stuff to maintain, which isn't going to be used very often. I think if you're going to run a profiler, you can run trial yourself.

[richvdh]

.

[ShadowJonathan]

How exactly would this add maintenance load? The only thing I can imagine is a gotcha for "oh, so I can just ignore !prof" when reading tox.ini, this change will only make it so that any test run is able to be profiled (which can be helpful if it's included in the tox config by default), which can then be added to CONTRIBUTING.md. Synapse swapped out plainly running trial with deterministic tox, adding a profiler option to it would only make sense, as every other option has already been folded into tox.

I understand if y'all dont wanna accept this PR, but if you really just wanna put a full dot on that decision, just close it.

[clokep]

How exactly would this add maintenance load? The only thing I can imagine is a gotcha for "oh, so I can just ignore !prof" when reading tox.ini

tox configs are already confusing enough to read and this adds additional cognitive load each time we need to modify it.

Synapse swapped out plainly running trial with deterministic tox, adding a profiler option to it would only make sense, as every other option has already been folded into tox.

I'm not sure what this means, I think most of the team runs tests directly via trial (and not using tox).

I agree with @richvdh's assessment.