🐛 Fix support for UnionType with Python 3.11

[jonaslb]

Fixes #533, which already had good details and a proposal for a solution, based on using get_args and get_origin from the typing module instead of the __args__ and __origin__ attributes. So I went and did that.

We also needed to actually handle the UnionType in addition to the Union from before.

Now there was a bit of a headache in terms of writing this in a backwards compatible way. What I've done is place the compatibility code into _compat_utils.py. But let me know if you'd prefer to keep it in main.py.

I also added a single test, just an adapted copy of another one with the x | None syntax. It is conditioned on Python >= 3.10, so it shouldn't fail on older Pythons.

[github-actions[bot]]

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[jonaslb]

It looks like mypy behaves differently in the different tests across versions. 3.6, 3.10 and 3.11 are ok, but 3.7, 3.8 and 3.9 are not. That seems confusing. I can maybe look at it another day again, otherwise if someone can see why it happens let me know.

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[jonaslb]

Failures are down to mypy version I think, it works fine here with latest. I see some errors in other places though (unrelated to my changes).

Also realized there is already another PR for this issue (just references other issue numbers, so I hadn't seen it): #522

Regardless, hope to see either PR merged. Ping @tiangolo

[austin-silk]

@tiangolo - can we merge this please?

[jonaslb]

Rebased on master and now all is green 👍

Still happy to make adaptations or answer questions.

[jonaslb]

@svlandeg I gather that #676 is the preferred solution to the UnionType situation? Should I just close this? Will we ever get anything on the topic merged - ie. what's blocking?

[svlandeg]

Hi @jonaslb, we've been going through the backlog of PRs to label them and connect related ones. We've already reviewed, adapted and merged a bunch for last week's releases 0.9.1 through 0.11.0. Open-source maintenance costs time and effort as I hope you can appreciate ;-) Thanks for your contributions (and patience) so far, we'll definitely get to this! It's fine to keep this one open in the meantime.

[jonaslb]

Open-source maintenance costs time and effort as I hope you can appreciate ;-)

Of course, and it's great to see that time is now being spent on typer also from the maintainer side ;-) I'm looking forward to engaging about details here if this PR turns out to be the preferred one out of the many submitted on the topic.

[lachaib]

Ruff tries to automatically fix these Optional[str] in my parameters and I had to disable it, so I'm really looking forward to seeing this merged and released.

[luispsantos]

@tiangolo I understand you have other time commitments and it must be overwhelming, but I would like to have this PR merged whenever possible. I use Ruff with pyupgrade rules like @lachaib and I find the lack of the modern union support a considerable hindrance when using Typer and Ruff together.

[tiangolo]

Great! Thank you for your contribution @jonaslb! :cake:

And in particular, thank you for your patience and your kindness. :hugs:

Thank you @svlandeg for the great job as always investigating, reviewing, and reporting everything. :bow:

This will be available in Typer 0.12.4, released in the next hours. :tada: