Advertise typing support

[alexfikl]

The main point of this was to add a py.typed marker so that users can get the typing annotations.

To make sure that all works nicely, it also

• Adds a barebones mypy configuration
• Adds a mypy step to the CI
• Fixes all the reported issues by mypy --strict.

[pierre-24]

Thank you, I did not know that it existed. There are small things to correct (thanks for correcting the lint error, btw), but we're almost good to go :)

[pierre-24]

That should be "Lexer" not None, then :)

[alexfikl]

__init__ always returns None (__new__ returns the type of the object)
https://docs.python.org/3/reference/datamodel.html#object.__init__

[pierre-24]

Oh, ok, I thought they were returning the Object itself. Good to know :)

[pierre-24]

Is this mandatory? :)

[alexfikl]

If I understand correctly, setuptools is the default at the moment
https://peps.python.org/pep-0518/#build-system-table
But I guess it's good to be explicit?

[pierre-24]

OK, then :)

[alexfikl]

Thank you, I did not know that it existed. There are small things to correct (thanks for correcting the lint error, btw), but we're almost good to go :)

Thanks for the very quick reply! Yeah, adding a py.typed empty file is required to let other packages know they can use the typing information:
https://peps.python.org/pep-0561/#packaging-type-information

[pierre-24]

Thank you :)

[alexfikl]

Thank you for the quick review! 😁