Implement mypy plugin for luigi.Task

[hiro-o918]

• Add Mypy Plugin to type-check arguments of luigi.Task

Description

• Implement a plugin for mypy inspired by dataclass

Note

• bump up sphinx version and use Python 3.10 for docs environment
  • because build failed on 3.9
  • 9b2e890
• After writing tests, Python 3.12 failed on mypy errros.
  • a0d8d2b

Motivation and Context

This PR aims to solve the following issues.

• the constructor of luigi.Task cannot be type-checked when initializing it.
• The following type annotation is invalid since luigi.Parameter() is not str

class Task:
  foo: str = luigi.Parameter()

Have you tested this? If so, how?

• This PR includes the Mypy tests and docs

[hiro-o918]

use python 3.10 because docs build failed on 3.9
python for flake 8 also updated as a represented environment

[hiro-o918]

This part shows errors when assign invalid type for task arguments

[dlstadther]

LGTM. Just a mention/question about python versions

[dlstadther]

Luigi still advertises to be 3.6 compatible. Though, support for 3.6 should be removed (readme reference, tox reference, github actions test execution, etc.).

[dlstadther]

I saw elsewhere in this PR that the mypy stuff requires 3.8 or later. What is the behavior when someone tries to use it with 3.6 or 3.7?

[hiro-o918]

I saw elsewhere in this PR that the mypy stuff requires 3.8 or later

Sorry about your confusing.
I made a mistake to set a type annotations like list[Any] which supported after 3.8
I fixed this issue, the tests worked on 3.6 and 3.7.
I did not check python 3.6 and 3.7 on the tests.

I'll check how it works on Python 3.6 via tests.
If the test become flaky, one of workaround is ommit supporting mypy plugion on 3.6

[hiro-o918]

After inspecting issues about python 3.6 and 3.7, some built-in features are lacking (e.g. some type annotation features like Final and Literal as well as dict behaviors).

Can I want to omit these versions for this plugin because this feature is not core required to use luigi?

[hiro-o918]

4744560

[dlstadther]

Yeah, i'm fine with the included solution (requiring a minimum python version to import and use the mypy plugin).

[dlstadther]

For some reason, the 3.9 version of docs and flake8 are being expected. Although I've approved the PR and am a maintainer of the project, I'm not being allowed to click merge due to 2 statuses missing.

[dlstadther]

To merge, we may require a Spotify employee who has the appropriate permissions. I think the CI is trying to wait on some of the tests expected by the master branch even though those same tests were updated to 3.10 and are running successfully.

@RRap0so , would you be able to look and possibly merge anyway? (I cannot merge, the button is grayed-out saying Required statuses must pass before merging).

[RRap0so]

@dlstadther all done 👍