workflows/ci: add codecov

[woodruffw]

See #28.

Signed-off-by: William Woodruff [email protected]

[woodruffw]

The CI is succeeding and coverage is being uploaded to Codecov correctly, but something on their side seems to think the CI is failing and that the uploaded coverage files are empty.

Ref: codecov/codecov-action#844

[woodruffw]

I dug in a little more, and the uploaded report looks correct: it's a file listing, followed by the raw SQLite coverage report (from coverage.py). So I'm wondering if Codecov's SQLite intake is broken; trying with XML now.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@68ec7f0). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #253   +/-   ##
=======================================
  Coverage        ?   70.53%           
=======================================
  Files           ?       15           
  Lines           ?      896           
  Branches        ?        0           
=======================================
  Hits            ?      632           
  Misses          ?      264           
  Partials        ?        0           

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[woodruffw]

Well, now it's passing and uploading and generating some kind of coverage statistics, but I don't understand why.

[woodruffw]

Okay, I'm giving up on Codecov; their endpoints aren't consistently available and I'm not seeing any indication that they're consuming coverage uploads correctly.

I'm going to refactor this PR to use GitHub artifacts, similar to pyca/cryptography.

[woodruffw]

Closing since the history here isn't relevant. We'll revisit this with the approach in #253 (comment) in a follow-up PR.