Annotated in Typer v0.9.0 is broken with from __future__ import annotations

[jfcherng]

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Example Code

from __future__ import annotations
import typer
from typing_extensions import Annotated


def main(
    name: str,
    lastname: Annotated[str, typer.Option(help="Last name of person to greet.")] = "",
    formal: Annotated[bool, typer.Option(help="Say hi formally.")] = False,
):
    """
    Say hi to NAME, optionally with a --lastname.

    If --formal is used, say hi very formally.
    """
    if formal:
        print(f"Good day Ms. {name} {lastname}.")
    else:
        print(f"Hello {name} {lastname}")


if __name__ == "__main__":
    typer.run(main)

Description

1. Execute the example, which is verbatim taken from https://typer.tiangolo.com/tutorial/options/help/#__tabbed_1_1 except that adding from __future__ import annotations to its first line.

2. The help text of args/opts are not shown.

   Actually I think all args for typer.Option and typer.Argument are neglected.

   

Operating System

Windows

Operating System Details

No response

Typer Version

0.9.0

Python Version

Python 3.11.3

Additional Context

No response

[aworkin]

I'm running into this same issue. from __future__ import annotations causes the annotation attribute of inspect.Parameter objects to be "stringized".

Where does this happen?

The issue starts in typer.utils.get_params_from_function(), at line 109 of typer/typer/utils.py. The signature returned by the inspect.signature() call contains inspect.Parameter objects whose annotations attributes are stringized.

Because these annotations are stringized, the subsequent calls to typer.utils._split_annotation_from_typer_annotations() [line 113] with those annotations fail to properly split the Typer annotations, as the check to typer._typing.get_origin() [line 98] returns str instead of Annotated.

How could this be fixed?

In Python 3.10 and higher, inspect.signature() has a new eval_str parameter [doc] as well as the addition of inspect.get_annotations() [doc].

For Python 3.9 and lower, the process is somewhat involved. The annotations how-to [doc] suggests emulating the behavior of inspect.get_annotations().

From the how-to:

In a nutshell, if you wish to evaluate a stringized annotation on an arbitrary object o:
If o is a module, use o.__dict__ as the globals when calling eval().
If o is a class, use sys.modules[o.__module__].__dict__ as the globals, and dict(vars(o)) as the locals, when calling eval().
If o is a wrapped callable using functools.update_wrapper(), functools.wraps(), or functools.partial(), iteratively unwrap it by accessing either o.__wrapped__ or o.func as appropriate, until you have found the root unwrapped function.
If o is a callable (but not a class), use o.__globals__ as the globals when calling eval().

[notadoktor]

Also running into this issue and going slightly mad trying to figure out what was happening.

[bodograumann]

Same here. Can we please convert this into a bug issue so it gains more visibility, @tiangolo ?

[julesbertrand]

@tiangolo I've run into the same bug using from __future__ import annotations in python 3.8 and 3.9

[bodograumann]

I just recently learned that from __future__ import annotations will be replaced by a new approach, that should hopefully solve all the outstanding issues: https://peps.python.org/pep-0649/

[svlandeg]

Related PR: #721

[tiangolo]

Thanks for the report @jfcherng and for the discussion everyone! 🤓

This was indeed (probably) solved by #721, available in Typer 0.9.3, released in the next few hours. 🚀

[bodograumann]

Yes it works now 🚀

[jfcherng]

I just found another bug about typing_extensions.Annotated and from __future__ import annotations.

#802