Using some_type | None syntax for type annotations causes error in python 3.11

[PhilReinhold]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the Typer documentation, with the integrated search.
• I already searched in Google "How to X in Typer" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to Typer but to Click.

Commit to Help

• I commit to help with one of those options 👆

Example Code

import typer
from datetime import datetime
print(typer.__version__)

app = typer.Typer()

@app.command()
def f(x: datetime | None = None):
    print(x)

if __name__ == "__main__":
    app()

Description

In python 3.10 this script runs as expected, but on 3.11 I get the following error

Traceback (most recent call last):
  File "/Users/pcrein/qdash/test.py", line 16, in <module>
    app()
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 328, in __call__
    raise e
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 311, in __call__
    return get_command(self)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 364, in get_command
    click_command = get_command_from_info(
                    ^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 577, in get_command_from_info
    ) = get_params_convertors_ctx_param_name_from_function(command_info.callback)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 553, in get_params_convertors_ctx_param_name_from_function
    click_param, convertor = get_click_param(param)
                             ^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 844, in get_click_param
    parameter_type = get_click_type(
                     ^^^^^^^^^^^^^^^
  File "/Users/pcrein/.pyenv/versions/qdash-3.11.0/lib/python3.11/site-packages/typer/main.py", line 773, in get_click_type
    raise RuntimeError(f"Type not yet supported: {annotation}")  # pragma no cover
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: Type not yet supported: datetime.datetime | None

Operating System

macOS

Operating System Details

No response

Typer Version

0.7.0

Python Version

3.11.0

Additional Context

I believe the issue is that for some reason, typing.get_type_hints is no longer converting the UnionType into a Union. I would suggest as a fix that get_click_param use typing.get_origin/get_args instead of __args__ and __origin__ attributes.

[domef]

I'm having the same issue. Using Union[type1, type2] with from typing import Union leads to the same error.

[raminqaf]

@tiangolo, Any updates on this feature?

[johnthagen]

Related to

• PEP 604 Support #348

[pdonorio]

Hi and thanks a lot for this great library!

I've run into this issue as well. May someone provide some guidance on what should be fixed,
in case someone would like to contribute to solve it?

[renardeinside]

I have the same issue with Python 3.10. Any advisory on how to fix this?

[lucasgadams]

Switching from str | None = None to Optional[str] = None worked for me.

[toppk]

Switching from str | None = None to Optional[str] = None worked for me.

That is a pretty good workaround, but for me it means that I have to configure my linters one way for modules that use typer and another way for the rest of the code.

[roganartu]

Switching from str | None = None to Optional[str] = None worked for me.

That is a pretty good workaround, but for me it means that I have to configure my linters one way for modules that use typer and another way for the rest of the code.

pyupgrade will respect type aliases, as will typer. It's unwieldy, but this means you can do the following without having to configure pyupgrade to keep runtime types:

OptionalStr = Optional[str]

main(
    foo: OptionalStr = typer.Argument(None),
) -> None:
    ...

[johnthagen]

For me, I'd rather use Optional[str] than making an alias named OptionalStr (that someone then has to look up to know exactly how it was defined).

I think the idea here is that we ideally want to use str | None as is the new, preferred style, that pyupgrade/Ruff also lint for.

[albertotb]

For me, I'd rather use Optional[str] than making an alias named OptionalStr (that someone then has to look up to know exactly how it was defined).

I think the idea here is that we ideally want to use str | None as is the new, preferred style, that pyupgrade/Ruff also lint for.

Agree, for now I've just disabled linting in that specific line, in Ruff you can do it with #noqa: UP007

[exislow]

It would be great to use str | None instead of Optional[]. @tiangolo: Any plans to implement this to support >= Python3.11?

[dolfandringa]

I am stuck between Typer not supporting the new python syntax with |None=None and pyupgrade refusing to add an option to skip code for a specific line. I guess I'll try this solution.....

Switching from str | None = None to Optional[str] = None worked for me.

That is a pretty good workaround, but for me it means that I have to configure my linters one way for modules that use typer and another way for the rest of the code.

pyupgrade will respect type aliases, as will typer. It's unwieldy, but this means you can do the following without having to configure pyupgrade to keep runtime types:

OptionalStr = Optional[str]

main(
    foo: OptionalStr = typer.Argument(None),
) -> None:
    ...

[funkindy]

Any updates on this?

[johnthagen]

@funkindy Waiting for @tiangolo to have time to review the MRs listed here

• 🚀 Roadmap #678 (comment)

[hongqn]

@funkindy Waiting for @tiangolo to have time to review the MRs listed here

• 🚀 Roadmap #678 (comment)

Obviously @tiangolo either has no time, or has no will.

[tiangolo]

Hello all! Thanks for the feedback. ☕

This should have been fixed by #548

It is now available in Typer 0.12.4 🚀

[tonjo]

Hello all! Thanks for the feedback. ☕

This should have been fixed by #548

It is now available in Typer 0.12.4 🚀

Just upgraded to Typer 0.12.4 but still same error:

TypeError: unsupported operand type(s) for |: 'str' and 'NoneType'

[tiangolo]

@tonjo please create a new discussion filling all the form data, including a minimal reproducible example we can copy and run to see your error.

Doing it with the original issue seems solved, so there's probably something different in your use case.

[pdonorio]

Hello all! Thanks for the feedback. ☕
This should have been fixed by #548
It is now available in Typer 0.12.4 🚀

Just upgraded to Typer 0.12.4 but still same error:

TypeError: unsupported operand type(s) for |: 'str' and 'NoneType'

Hey @tonjo have you created a new issue?

I'm getting the same issue if I try the operand inside "Annotated"

app.command('some')
def some(
  option: Annotated[list | str, typer.Option()] = None,
):
   ...

In case I can open a new Issue if you didn't do it yet

[pypae]

@tonjo
Are you on Python 3.10+? Union type expressions were added in 3.10.

If you're getting the following error, you're probably on an earlier version:

TypeError: unsupported operand type(s) for |: 'str' and 'NoneType'

---

@pdonorio
I think there are two issues with your example:

• If I understand correctly, typer does still not support all Union types, only Optional X | None using the 3.10+ syntax. The wording in the release notes were not very clear about that.
• list cannot be used without a specific type for the list items. e.g. list[str]

app.command('some')
def some(
  option: Annotated[list | str, typer.Option()] = None,  # the following would work: option: Annotated[list[str] | None, typer.Option()] 
):
   ...

[pdonorio]

• If I understand correctly, typer does still not support all Union types, only Optional X | None using the 3.10+ syntax. The wording in the release notes were not very clear about that.
• list cannot be used without a specific type for the list items. e.g. list[str]

Thanks, using list[str] on the latest works @pypae 🙏

[tonjo]

@pypae I'm using python 3.12.

Not using typer directly, though, it's an issue with sqlmodel, when defining an optional
field using a string (because that model is not defined yet), that error is thrown.

But maybe it is not the right place to comment to, as @tiangolo suggested.

[TiansuYu]

Somehow still broken under python 3.10, typer 0.12.5.

max_tokens: Annotated[int | None, typer.Option(help="Max tokens")] = None,

max_tokens
  Input should be a valid integer [type=int_type, input_value=None, input_type=NoneType]
    For further information visit https://errors.pydantic.dev/2.9/v/int_type

Somehow the validation did not pass to pydantic correctly

[NikosAlexandris]

❯ python --version
Python 3.11.9

and

❯ ipython -c "import typer; print(typer.__version__)"
0.12.5

or indeed version 0.12.4 as well, I still get

AssertionError: Typer Currently doesn't support Union types

Downgrading back to 0.12.3 complains then about

RuntimeError: Type not yet supported: float | None

Though, I have more "unions", also in the form of X | Y | None.

[NikosAlexandris]

Somehow still broken under python 3.10, typer 0.12.5.

max_tokens: Annotated[int | None, typer.Option(help="Max tokens")] = None,

max_tokens
  Input should be a valid integer [type=int_type, input_value=None, input_type=NoneType]
    For further information visit https://errors.pydantic.dev/2.9/v/int_type

Somehow the validation did not pass to pydantic correctly

This means you are bound to Python 3.10 ? In 3.11 (which is how this thread begun) it works.

[TiansuYu]

If I remember correctly, the <type> | None syntax is introduced in 3.10. Therefore Typer should test it against 3.10 as well IMO. But it seems that withTyper 0.12.5, I no longer has this issue any more.

[NikosAlexandris]

❯ python --version
Python 3.11.9

and

❯ ipython -c "import typer; print(typer.__version__)"
0.12.5

or indeed version 0.12.4 as well, I still get

AssertionError: Typer Currently doesn't support Union types

Downgrading back to 0.12.3 complains then about

RuntimeError: Type not yet supported: float | None

Though, I have more "unions", also in the form of X | Y | None.

Indeed the problem here is more complex unions. I removed these for now and it works. But why not add support for it ?

[TiansuYu]

Indeed the problem here is more complex unions. I removed these for now and it works. But why not add support for it ?

Indeed, i think Typer should support it (at least for all current python type annotations). In the future, i would hope that it supports all pydantic basemodel types as well.

[NikosAlexandris]

I think a "fix" would need to go around https://github.com/fastapi/typer/blob/master/typer/main.py#L844-L852.

[svlandeg]

Closing this issue as the original topic/problem has been addressed by #548. Thanks for all the discussion! If there are remaining/related issues, please open a new discussion thread - it's easier to have one specific topic per thread 🙏