setup coverage.py in tox env

[H-Shay]

Hopefully this satisfies the first part of #200 (comment). If so, I'll move on to adding reports to Github actions, etc. Thanks!

[H-Shay]

Noting that the towncrier github actions check is failing. Looks like an error with a config file somewhere (git produced output while failing:
fatal: ambiguous argument 'origin/master...': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git [...] -- [...]')
I didn't experience this error when setting up the github actions so I'm a little perplexed, but I will look deeper into it tomorrow.

[anoadragon453]

The command that towncrier is running is git diff --name-only origin/master..., and failing to figure out what origin/master is. There's a lot of possible reasons for this. checkout@v2 might be specifying your fork as origin, and may only be checkout out your add-coverage branch but nothing else. It may be possible to fix this by just doing a git fetch origin before running towncrier.

I'd probably play around in this PR (or another) and try to get some information out of GitHub Actions in terms of how it's set it's remotes and branches up.

[callahad]

Looks good!

• Let's add .coverage* and htmlcov/ to the .gitignore file and remove them from this pull request; no need to ship the reports with our source.
• It would probably be good to run coverage report --sort=cover and coverage html so that there's something in the console as well as the html if you want to delve deeper.
• ...and maybe only run the report(s) if the initial -m twisted.trial succeeds?

[callahad]

As to the towncrier bit... by default GitHub Actions does a shallow clone of the repo which has only one commit: the result of the proposed merge. So there's no actual history there to compare against. Solving that properly is a bit of a rabbit hole, but I think setting:

- uses: actions/checkout@v2
  with:
    fetch-depth: 0
    ref: ${{ github.event.pull_request.head.sha }}

would get you a full history, check out the actual branch head (not the proposed merge) and allow the check to work.

[H-Shay]

Ok cool I will open a different PR for the towncrier issue and see if I can't get it working using the insight you both offered.

I've updated the PR to add the other changes related to coverage. However I have one question:

In terms only running the coverage reports if the -m twisted.trial succeeds, I am wondering if tox doesn't do this automatically? Looking at the docs, under commands it states that "Commands will execute one by one in sequential fashion until one of them fails (their exit code is non-zero) or all of them succeed." My understanding of this is that tox will exit if the twisted.trial fails. I am unfamiliar with tox so please correct me if I'm wrong!

[callahad]

"Commands will execute one by one in sequential fashion until one of them fails (their exit code is non-zero) or all of them succeed."

Oh, cool! You're probably totally good there, then :)

[H-Shay]

Great then this should be all set to go!

[richvdh]

@callahad I think you have most context here so if you have the cycles to pick up the review that would be appreciated!

[callahad]

Great, thanks! Could you please:

1. Merge origin/master (or rebase onto origin/master) so we can get working towncrier checks
2. Add coverage~=5.5 as a dependency somewhere to ensure that a cleantox virtual environment has access to it? (e.g., it could be a dev dependency in setup.py, or a one-off deps entry in the tox.ini testenv.

[H-Shay]

Alright I think that did it. Thank you!

[callahad]

We're almost good :) The tox.ini still needs to be adjusted to actually install coverage in the default testenv. You can just remove the extras = stanza from the other environments and put it straight in the base testenv and then all three will inherit it and install the dev dependencies.

[H-Shay]

Thanks for the hand-holding, I am actually learning a lot. Hopefully this is the last update!

[callahad]

Thank you so much!

[callahad]

Oh, hey, could you sign-off on a commit in this branch, please?

You can do a git commit --signoff --allow-empty to make an empty commit to that effect :)