Add types to _unix_pipes

[harahu]

Complete type annotations for the _unix_pipes module.

[codecov]

Codecov Report

Merging #2502 (f207b2b) into master (52eab84) will increase coverage by 0.86%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2502      +/-   ##
==========================================
+ Coverage   97.98%   98.84%   +0.86%     
==========================================
  Files         118      118              
  Lines       16324    16327       +3     
  Branches     3156     3156              
==========================================
+ Hits        15995    16139     +144     
+ Misses        266      133     -133     
+ Partials       63       55       -8     

Impacted Files	Coverage Δ
trio/_unix_pipes.py	100.00% <100.00%> (ø)
trio/_core/_run.py	99.45% <0.00%> (+0.43%)	⬆️
trio/tests/test_socket.py	99.83% <0.00%> (+0.64%)	⬆️
trio/_core/tests/test_io.py	100.00% <0.00%> (+1.05%)	⬆️
trio/tests/test_highlevel_open_tcp_stream.py	100.00% <0.00%> (+1.47%)	⬆️
trio/_subprocess_platform/__init__.py	100.00% <0.00%> (+5.71%)	⬆️
trio/_core/__init__.py	100.00% <0.00%> (+12.50%)	⬆️
trio/lowlevel.py	100.00% <0.00%> (+16.66%)	⬆️
trio/_core/_io_kqueue.py	84.67% <0.00%> (+83.87%)	⬆️
trio/_subprocess_platform/kqueue.py	100.00% <0.00%> (+100.00%)	⬆️

[pquentin]

Thanks! This looks good, but how did you test it? Is running mypy on this file working? If so we should do it in CI too.

[harahu]

This looks good, but how did you test it? Is running mypy on this file working?

@pquentin I tested it by running mypy on the file. It is working.

If so we should do it in CI too.

We already are, for python 3.8 at least: https://github.com/python-trio/trio/actions/runs/3683469595/jobs/6232645740

(Look at the bottom of the "Run tests" step)

[pquentin]

This makes sure that the annotations are valid, but not that they are complete. If tomorrow I add a new function to this file without annotations mypy won't complain about it.

It's not blocking for this pull request but we should strive to have complete annotations for each file and enforce that in CI using mypy --strict. This approach was used successfully by urllib3.

[harahu]

It's not blocking for this pull request but we should strive to have complete annotations for each file and enforce that in CI using mypy --strict. This approach was used successfully by urllib3.

I'm aware that this technique has been used with success, and I'm a fan of introducing it. Doing so should be a separate PR. I might look into it soon.

For now, though, annotation coverage is so low that regressing coverage is the least of my worries.