Add typing annotation and improve linting during CI checks.

[sodul]

I noticed several issues that would be captured by mypy. I suggest adding mypy to the CI checks and start adding type annotation in the codebase.

I would start with minimal mypy checks, with the latest main I find these:

> mypy .  
green/config.py:9: error: Cannot find implementation or library stub for module named "ConfigParser"  [import]
green/config.py:9: error: Name "configparser" already defined (by an import)  [no-redef]
green/suite.py:3: error: Module "unittest.suite" has no attribute "_call_if_exists"  [attr-defined]
green/suite.py:3: error: Module "unittest.suite" has no attribute "_DebugResult"  [attr-defined]
green/suite.py:3: error: Module "unittest.suite" has no attribute "_isnotsuite"  [attr-defined]
green/process.py:215: error: Cannot assign multiple types to name "LoggingDaemonlessPool" without an explicit "Type[...]" annotation  [misc]
green/process.py:215: error: Incompatible types in assignment (expression has type "Type[LoggingDaemonlessPool37]", variable has type "Type[LoggingDaemonlessPool38]")  [assignment]
green/process.py:219: error: Module "multiprocessing.pool" has no attribute "MaybeEncodingError"  [attr-defined]
green/process.py:308: error: Module has no attribute "worker"  [attr-defined]
green/djangorunner.py:27: error: Need type annotation for "ALLOWED_HOSTS" (hint: "ALLOWED_HOSTS: List[<type>] = ...")  [var-annotated]
green/djangorunner.py:68: error: Skipping analyzing "django": module is installed, but missing library stubs or py.typed marker  [import]
green/djangorunner.py:72: error: Skipping analyzing "django.test.runner": module is installed, but missing library stubs or py.typed marker  [import]
green/djangorunner.py:134: error: Cannot assign to a type  [misc]
green/djangorunner.py:134: error: Incompatible types in assignment (expression has type "Callable[[], Any]", variable has type "Type[DjangoRunner]")  [assignment]
green/test/test_runner.py:25: error: Cannot find implementation or library stub for module named "testtools"  [import]
green/test/test_runner.py:148: error: Not all arguments converted during string formatting  [str-format]
green/test/test_runner.py:176: error: Not all arguments converted during string formatting  [str-format]
green/test/test_runner.py:211: error: Not all arguments converted during string formatting  [str-format]
green/test/test_runner.py:237: error: Not all arguments converted during string formatting  [str-format]
green/test/test_runner.py:265: error: Not all arguments converted during string formatting  [str-format]
green/command.py:6: error: Incompatible import of "Command" (imported name has type "Type[distutils.cmd.Command]", local name has type "Type[setuptools.Command]")  [assignment]
green/test/test_djangorunner.py:126: error: Skipping analyzing "django.core.management.commands.test": module is installed, but missing library stubs or py.typed marker  [import]
green/test/test_command.py:10: error: Cannot find implementation or library stub for module named "distutil.dist"  [import]
green/test/test_command.py:10: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
green/test/test_command.py:10: error: Name "Distribution" already defined (possibly by an import)  [no-redef]
Found 24 errors in 8 files (checked 41 source files)

This is with mypy 1.2.0 and Python 3.11.3.

I can create a PR with the updated check, and the fixes for the issues. I would add type annotation on the existing codebase, backward compatible with python 3.6.

Do you have any preference for linting the codebase? Pylint is a classic, and we use it to great success, the modern one is Ruff which is very fast but does not have as many rules as Pylint provides.

[CleanCut]

I'm fine trying your preference out and seeing how it goes. 👍🏻

[sodul]

Now that we have comprehensive type annotation in main we can close this conversation.