PEP484 type annotate all of bandersnatch

[cooperlees]

Lets add PEP484 type annotations to all source code and get clean passing mypy checks.

Mypy: http://mypy.readthedocs.io/en/stable/getting_started.html
typing module: https://docs.python.org/3/library/typing.html

[pradyunsg]

Useful tools here:

• https://github.com/dropbox/pyannotate
• https://github.com/Instagram/MonkeyType

[cooperlees]

Ok - Only plugins left to strictly type annotate. Help welcome or I'll eventually get to it.

[cooperlees]

I didn't mean to close this! We are getting close tho!

[rkm]

Hi! I can probably finish this off if you can point me in the right direction

[cooperlees]

No problem. What's left is all the test code here:

https://github.com/pypa/bandersnatch/tree/master/src/bandersnatch/tests

How I'd go about this

• Remove src/bandersnatch/tests/.* from https://github.com/pypa/bandersnatch/blob/master/.pre-commit-config.yaml#L33
• Make a virtualenv - install requrements.txt + requirements_dev.txt
• run mypy and make it all pass :D

[rkm]

hi, just a quick update. I've made a start on this here: master...rkm:issue/15-pep484-type-annotations. Turns out pytest is not very pep484-friendly currently, so I've had to import some of its private members to keep mypy happy. Interested to hear any suggestions!

some related issues:

• pytest typing - Support for static typing pytest-dev/pytest#3342
• false unreachable after pytest.raises block - false unreachable error after pytest.raises block python/mypy#8985

[cooperlees]

Awesome stuff! Really appreciate the efforts. I'm also open to accepting some PRs that partly make this work and to divide up your remaining plan. I knew this would not be a super easy PR to finish. Also happy to accept plenty of # type: ignores and we can try go back through them as things gets resolved - e.g. pytest 6 arrives.

If you'd like more real time chat we can do that too on IRC - irc.freenode.net #bandersnatch. We have a few active maintainers hang out in there very regularly now!