Type fixes

[DeviousStoat]

fixes #231

[DeviousStoat]

I have no idea why we get these mypy syntax errors though. Doesn't even seem to point to the right line and I can't seem to be able to reproduce locally. I will try to figure it out later today

[dgilland]

I can reproduce it locally if I delete the .mypy_cache folder and then run mypy (but only on the first run):

$ rm -r .mypy_cache
$ inv mypy
src/pydash/numerical.py:104:68: error: X | Y syntax for unions requires Python 3.10  [syntax]
src/pydash/arrays.py:104:68: error: X | Y syntax for unions requires Python 3.10  [syntax]
src/pydash/objects.py:104:68: error: X | Y syntax for unions requires Python 3.10  [syntax]
$ inv mypy
$

I don't think there's even any X | Y type syntax being used either, which makes me think it might be an issue with mypy.

[DeviousStoat]

I think I found the issue. It happens when using the SupportsRichComparisonT type variable.

It is defined in the python base library typesheds. When we are using a >=3.10 python version mypy will use the >=3.10 typesheds and the definition is

SupportsRichComparison: TypeAlias = SupportsDunderLT[Any] | SupportsDunderGT[Any]
SupportsRichComparisonT = TypeVar("SupportsRichComparisonT", bound=SupportsRichComparison)

And in the pyproject.toml mypy section we have python_version = "3.8" so it fails when type checking using the 3.10 typeshed with the X | Y union syntax that is used in the typeshed. If we set python_version = "3.10" it works. But I don't think we want that, we probably want mypy to check using the lowest supported python version.

One other thing that fixes it is adding from __future__ import annotations on top of the affected modules. This allows using the X | Y syntax in <3.10 python version. It also postpones the evaluation of annotations so we could write collection: t.Mapping[t.Any, SupportsRichComparisonT], default: Unset = UNSET instead of collection: t.Mapping[t.Any, "SupportsRichComparisonT"], default: Unset = UNSET for type variable that are imported only during TYPE_CHECKING.

Otherwise we could redefine the SupportsRichComparison values inside the library.

I think the from __future__ import annotations is probably the best solution, it's a good practice to support different python versions with mypy. Let me know what you think.

[dgilland]

From future import seems best.

[DeviousStoat]

neat, everything passes now :D