Add mypy check

[blink1073]

Minimal typings support, mostly as a linter for now.

Uses new typings from jupyter_client.

I'm working on shipping minimal typings with traitlets and jupyter_core as well.

[codecov-commenter]

Codecov Report

Merging #779 (d438492) into main (eff1b08) will decrease coverage by 0.09%.
The diff coverage is 62.96%.

@@            Coverage Diff             @@
##             main     #779      +/-   ##
==========================================
- Coverage   70.21%   70.12%   -0.10%     
==========================================
  Files          63       63              
  Lines        7494     7544      +50     
  Branches     1258     1258              
==========================================
+ Hits         5262     5290      +28     
- Misses       1851     1873      +22     
  Partials      381      381              

Impacted Files	Coverage Δ
jupyter_server/auth/login.py	70.92% <0.00%> (ø)
jupyter_server/gateway/handlers.py	30.90% <0.00%> (-0.97%)	⬇️
jupyter_server/pytest_plugin.py	88.18% <0.00%> (ø)
jupyter_server/utils.py	62.37% <0.00%> (ø)
jupyter_server/gateway/managers.py	58.22% <39.28%> (-1.45%)	⬇️
jupyter_server/extension/handler.py	67.18% <53.33%> (+1.05%)	⬆️
jupyter_server/serverapp.py	65.25% <57.14%> (-0.07%)	⬇️
jupyter_server/services/contents/handlers.py	85.46% <60.00%> (ø)
jupyter_server/files/handlers.py	34.48% <66.66%> (+1.14%)	⬆️
jupyter_server/services/sessions/sessionmanager.py	88.26% <66.66%> (ø)
... and 14 more

---

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[Zsailer]

I think this is going to cause some pain for other PRs that will need to rebase. Maybe we should wait until (at least) identity is merged?

[blink1073]

Sounds fair, will mark as 2.0

[blink1073]

This is ready now

[blink1073]

I plan to merge this and cut the first alpha release tomorrow.

[Zsailer]

Do you think we should backport these changes?

I ask, because if we merge this and don't backport it, do you think it will cause issues for future backports? It seems like future backports might have conflicts with changes here and cause meeseeks to choke.

[blink1073]

Good point, I'll take care of the backporting of this one.

[blink1073]

@meeseeksdev please backport to 1.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 1.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 3e64fa5eef7fba9f8e17c30cec688254adf913bd

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #779: Add mypy check'

4. Push to a named branch:

git push YOURFORK 1.x:auto-backport-of-pr-779-on-1.x

5. Create a PR against branch 1.x, I would have named this PR:

"Backport PR #779 on branch 1.x (Add mypy check)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.