run io_bound and cpu_bound maintain type signatures of their callbacks

[petergaultney]

This is a pretty simple way for nicegui to not 'drop' the types of callbacks that need to get run in the background for whatever reason. I know mypy supports this, and I'm pretty sure other type checkers do too. It's an official part of the type system.

For this code:

we go from

to

And (although i have no accompanying screenshots) you would also get type checking on your inputs to the function.

[falkoschindler]

Thanks for this pull request, @petergaultney! I really like filling these gaps of missing type annotations.

Just one remark: I would prefer explicitly ignoring the mypy warning (# type: ignore) instead of casting it to R, creating a "lie". What do you think?

[petergaultney]

Thanks for this pull request, @petergaultney! I really like filling these gaps of missing type annotations.

Just one remark: I would prefer explicitly ignoring the mypy warning (# type: ignore) instead of casting it to R, creating a "lie". What do you think?

I think the outer return type R is still a lie in a sense - ignore and cast both let us violate the type system. But I can see how ignore might seem a little less confusing to readers of this code. I'll change that over.

[falkoschindler]

Thanks again, @petergaultney!
Let's merge! 🚀