Render union types using |

[flying-sheep]

Python encourages using | over Union and Optional. s-a-t should therefore render unions that way by default.

See here for more context.

Of note is the argument that Optional is actually misleading, since it implies something that doesn’t exist in Python:

• R has true support for optional parameters via missing(param), which returns TRUE only when the function was called without specifying param.
• Contrast with Python, where param: int | None = 4 is perfectly meaningful, while the same expressed as param: Optional[int] = 4 is very confusing: The Optional seems to relate to the fact that the parameter can be left out when calling the function, but actually means that you can specify param=None to override the default of 4. Weird!

[gboeing]

I am in total agreement with @flying-sheep. This would be a really great improvement.

[gaborbernat]

I'll review a PR if someone puts one in 👍 doing the change.

[gboeing]

Thanks @gaborbernat.

@flying-sheep are you open to creating a PR for what you proposed?

[flying-sheep]

I would, but #418 already exists. Also, I don‘t think it needs to be an option, it should just be how things are done, no?

[gboeing]

That was a quick PR! @flying-sheep I agree with you regarding the option... I'll leave a comment on the PR.