Custom type with default does not typecheck

[danielroseman]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the Typer documentation, with the integrated search.
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• I already read and followed all the tutorials in the docs and didn't find an answer.
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Example Code

import typer
from typing_extensions import Annotated


class CustomClass:
    def __init__(self, value: str):
        self.value = value

    def __str__(self):
        return f"<CustomClass: value={self.value}>"


def parse_custom_class(value: str):
    return CustomClass(value * 2)


def main(
    custom_arg: Annotated[CustomClass, typer.Argument(parser=parse_custom_class)],
    custom_opt: Annotated[CustomClass, typer.Option(parser=parse_custom_class)] = "Foo",
):
    print(f"custom_arg is {custom_arg}")
    print(f"--custom-opt is {custom_opt}")


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

Description

The above code, which is directly from https://github.com/tiangolo/typer/blob/master/docs_src/parameter_types/custom_types/tutorial001_an.py, does not type check correctly.

Mypy gives:

error: Incompatible default for argument "custom_opt" (default has type "str", argument has type "CustomClass")  [assignment]

Operating System

macOS

Operating System Details

No response

Typer Version

0.12.3

Python Version

3.12.3

Additional Context

mypy version 1.10.0

[danielroseman]

Sorry, even though I searched before posting, I've just now seen that this is a duplicate of
#720