Add mypy

[dongkyunc]

What

Adds mypy and django-stubs

Why

Static type checking is nice

How

• Add package to `requirements.{in,txt}
• Add settings to `web/main/config.
• Add .github/workflows/mypy.yml
• Change some lines that were making mypy mad

Notes to Reviewers

• web/main/admin.py is ignored, along with any imports that may affect
• Originally, check_untyped_defs was passed in as an option, there were errors I did not know how to fix due to an unfamiliarity with the codebase
• typing.Sequence is unused, but it's making mypy mad if it isn't there for some reason.
  

[codecov-commenter]

Codecov Report

Merging #1639 (e4c3382) into develop (c489b8a) will increase coverage by 0.01%.
The diff coverage is 93.93%.

@@             Coverage Diff             @@
##           develop    #1639      +/-   ##
===========================================
+ Coverage    75.77%   75.78%   +0.01%     
===========================================
  Files           43       43              
  Lines         5986     5997      +11     
===========================================
+ Hits          4536     4545       +9     
- Misses        1450     1452       +2     

Impacted Files	Coverage Δ
web/main/admin.py	70.07% <ø> (ø)
web/main/models.py	74.63% <92.59%> (+0.03%)	⬆️
web/config/urls.py	83.33% <100.00%> (ø)
web/config/wsgi.py	80.00% <100.00%> (ø)
web/reporting/admin/__init__.py	100.00% <100.00%> (ø)
web/reporting/admin/views.py	98.08% <100.00%> (ø)

---

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[lizadaly]

Thanks for taking this on!

When I looked at this in #1615 it seemed valuable to install the type stubs for some of the imported packages too.

I recommend deferring the mypy Github Action for now. We probably want to combine all three of pyflakes, black, and mypy into a single workflow to avoid too much overhead in spinning up containers. (There's a Github Action quota for private repositories but that wouldn't seem to apply here.)

[rebeccacremona]

Hooray for adding support for type annotation!

I have a bunch of little questions.

[rebeccacremona]

Cool, thanks for doing this, and sorry to be so slow with approving the changes!!

I'm going to take the liberty of pushing a few commits.

Stubs

I pulled this code down and ran docker compose exec web mypy . and got the following errors:

rcremona@HLSNHJGWY2X2J h2o % docker compose exec web mypy .
main/sanitize.py:1: error: Library stubs not installed for "bleach" (or incompatible with Python 3.9)
main/sanitize.py:1: note: Hint: "python3 -m pip install types-bleach"
main/utils.py:15: error: Library stubs not installed for "requests" (or incompatible with Python 3.9)
main/models.py:8: error: Library stubs not installed for "dateutil.parser" (or incompatible with Python 3.9)
main/models.py:8: note: Hint: "python3 -m pip install types-python-dateutil"
main/models.py:8: note: (or run "mypy --install-types" to install all missing stub packages)
main/models.py:8: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
main/models.py:8: error: Library stubs not installed for "dateutil" (or incompatible with Python 3.9)
main/models.py:13: error: Library stubs not installed for "requests" (or incompatible with Python 3.9)
main/models.py:13: note: Hint: "python3 -m pip install types-requests"
reporting/admin/views.py:5: error: Library stubs not installed for "dateutil.relativedelta" (or incompatible with Python 3.9)
reporting/admin/usage_dashboard.py:10: error: Library stubs not installed for "dateutil.relativedelta" (or incompatible with Python 3.9)
Found 7 errors in 5 files (checked 88 source files)

I bet you ran mypy --install-types in your environment? I'm going to add all those stubs to requirements.[in, txt] so that they will be installed in the Docker image. Then, subsequent to pip-compile and pip-sync:

docker compose exec web mypy .
Success: no issues found in 88 source files

Regarding typing.Sequence

This turns out to be a known bug with the handling of custom model managers. As per the docs, QuerySet.as_manager() is not yet supported. But the workaround they suggest, Manager.from_queryset, as of the latest release, runs into django-stubs#1022... which is fixed in the merged, but as-yet-unreleased django-stubs#1028.

I installed from the merged commit:

docker compose exec web bash -c "yes | pip uninstall django-stubs"
docker compose exec web pip install git+https://github.com/typeddjango/django-stubs.git@84eff755661c3c498c36e66b7ff0b6cc8fc3d4bb

And behold:

docker compose exec web mypy main/models.py
Success: no issues found in 1 source file

Version 1.12.0 was released on June 17, 2022; hopefully that means we won't have to wait long for the next release!

I added a comment to that effect.

[rebeccacremona]

Now let's see if I'm smart enough to resolve the merge conflict using the Github UI 😅

[lizadaly]

@rebeccacremona I can do this in a bit if you want since I'm more familiar with the code.

[rebeccacremona]

@rebeccacremona I can do this in a bit if you want since I'm more familiar with the code.

whoops, thanks, didn't see this!