[BUG] typing_extensions.Annotated cannot be used with from __future__ import annotations in py38

[jfcherng]

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Example Code

from __future__ import annotations

import typer
from typing_extensions import Annotated


def main(force: Annotated[bool, typer.Option("--force")] = False):
    if force:
        print("Forcing operation")
    else:
        print("Not forcing")


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

Description

This issue only happens with Python ≤ 3.8 because as of py39, typing_extension.Annotated just uses typing.Annotated in https://github.com/python/typing_extensions/blob/c79c561ec62a09e5a62d14c12ccae4d7cb273da0/src/typing_extensions.py#L1167-L1174.

The above is taken from the official tutorial and adding from __future__ import annotations to its first line. And then running the above code gives the following error:

╭─────────────────────────────── Traceback (most recent call last) ────────────────────────────────╮
│ D:\jfcherng\Desktop\test.py:15 in <module>                                                       │
│                                                                                                  │
│   12                                                                                             │
│   13                                                                                             │
│   14 if __name__ == "__main__":                                                                  │
│ ❱ 15 │   typer.run(main)                                                                         │
│   16                                                                                             │
│                                                                                                  │
│ ╭─────────────────────────────────────────── locals ───────────────────────────────────────────╮ │
│ │   Annotated = <class 'typing_extensions.Annotated'>                                          │ │
│ │ annotations = _Feature((3, 7, 0, 'beta', 1), (3, 10, 0, 'alpha', 0), 16777216)               │ │
│ │        main = <function main at 0x000001368BD7F310>                                          │ │
│ │       typer = <module 'typer' from                                                           │ │
│ │               'D:\\jfcherng\\Desktop\\.venv\\lib\\site-packages\\typer\\__init__.py'>        │ │
│ ╰──────────────────────────────────────────────────────────────────────────────────────────────╯ │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:1067 in run                            │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:326 in __call__                        │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:309 in __call__                        │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:362 in get_command                     │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:579 in get_command_from_info           │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:555 in                                 │
│ get_params_convertors_ctx_param_name_from_function                                               │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:859 in get_click_param                 │
│                                                                                                  │
│ D:\jfcherng\Desktop\.venv\lib\site-packages\typer\main.py:788 in get_click_type                  │
╰──────────────────────────────────────────────────────────────────────────────────────────────────╯
RuntimeError: Type not yet supported: typing_extensions.Annotated[bool, <typer.models.OptionInfo object at
0x000001368BEFCFD0>]

Operating System

Windows

Operating System Details

No response

Typer Version

0.12.3

Python Version

3.8

Additional Context

venv packages:

(Desktop) $ uv pip install typer typing_extensions
Resolved 9 packages in 7ms
Installed 9 packages in 506ms
 + click==8.1.7
 + colorama==0.4.6
 + markdown-it-py==3.0.0
 + mdurl==0.1.2
 + pygments==2.17.2
 + rich==13.7.1
 + shellingham==1.5.4
 + typer==0.12.3
 + typing-extensions==4.11.0

[ivantodorovich]

I've noticed the same thing.

To add to your report: I've tested with python versions 3.8, 3.9, 3.10, 3.11 and 3.12.
The only version where this fails is 3.8.

[jfcherng]

Thanks for more information. I found that typing.Annotated is introduced in py39. And thus typing_extensions.Annotated is just forwarded to typing.Annotated as of py39 in https://github.com/python/typing_extensions/blob/c79c561ec62a09e5a62d14c12ccae4d7cb273da0/src/typing_extensions.py#L1167-L1174 so it's expected to work in py>=39 while py38 is a special case.

[ivantodorovich]

In addition to that, digging into typer, what I notice is that param.annotation here is a string:

typer/typer/utils.py

Line 119 in d1a177c

param.annotation,

e.g.: 'Annotated[int, typer.Argument()]' in my case

Then, because of that, typer fails to "split annotations from typer annotations" here:

typer/typer/utils.py

Lines 99 to 100 in d1a177c

	if get_origin(base_annotation) is not Annotated: # type: ignore
	return base_annotation, []

[ivantodorovich]

In fact it seems this has already been analized: #598 (comment)

On that comment the "How could this be fixed?" section is pretty clear. The solution for python3.8 and python3.9 suggested there is correct IMO.

The thing is the PR that solved this issue fixed it only for >= 3.10 (#721)

I don't know why on my tests 3.9 succeeds, though. I need to re-check that.

[ivantodorovich]

I proposed a fix here: #814
It was rather simple to fix in the end ^^

[jfcherng]

Great investigation @ivantodorovich 👍

---

Fwiw, I can monkey patch it before that PR gets merged.

import typer.utils
from typing_extensions import Annotated, get_type_hints
setattr(typer.utils, "get_type_hints", get_type_hints)