Enum Arguments/Options with custom click_type are always None

[AlessandroPomponio]

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Example Code

import enum
from typing import Any, Optional

import click
import typer
from typer.testing import CliRunner


def test_custom_click_type_enum():
    class OnlyOneCatEnum(enum.Enum):
        CAT = "cat"

    class NoPluralCatsChoice(click.Choice):
        name = "single_cat"

        def convert(
            self,
            value: Any,
            param: Optional[click.Parameter],
            ctx: Optional[click.Context],
        ) -> Any:
            if value.endswith("s"):
                value = value[:-1]
            return OnlyOneCatEnum(value)

    app = typer.Typer()

    @app.command()
    def custom_click_type_enum(
        ctx: typer.Context,
        animal: OnlyOneCatEnum = typer.Argument(
            None, click_type=NoPluralCatsChoice(choices=["cat"])
        ),
        animal_option: OnlyOneCatEnum = typer.Option(
            None, click_type=NoPluralCatsChoice(choices=["cat"])
        ),
    ):
        assert (
            ctx.params["animal"] == OnlyOneCatEnum.CAT
        ), "The animal param was not a cat!"
        assert (
            ctx.params["animal_option"] == OnlyOneCatEnum.CAT
        ), "The animal_option param was not a cat!"
        assert animal == OnlyOneCatEnum.CAT, "The animal Argument was not a cat!"
        assert (
            animal_option == OnlyOneCatEnum.CAT
        ), "The animal_option Option was not a cat!"

    result = CliRunner().invoke(app, ["cats", "--animal-option", "cats"])
    assert result.exit_code == 0

Description

When I define a custom Click type using Enums and set the click_type, i see that:

• ctx.params[parameter_name] has the correct value set
• parameter_name is instead None

This does not appear to happen with Click, where the relevant piece of code becomes:

    @click.command()
    @click.argument("animal", type=NoPluralCatsChoice(["cats"]))
    @click.option("--animal-option", type=NoPluralCatsChoice(["cats"]))
    @click.pass_context
    def custom_click_type_enum(
        ctx: click.Context,
        animal: NoPluralCatsChoice,
        animal_option: NoPluralCatsChoice,
    ):
        assert animal == OnlyOneCatEnum.CAT, "The animal Argument was not a cat!"
        assert (
            animal_option == OnlyOneCatEnum.CAT
        ), "The animal_option Option was not a cat!"

    result = CliRunner().invoke(
        custom_click_type_enum, ["cats", "--animal-option", "cats"]
    )
    assert result.exit_code == 0

Operating System

macOS

Operating System Details

No response

Typer Version

0.11.0

Python Version

Python 3.10.12

Additional Context

No response

[brianmedigate]

If you return value rather than OnlyOneCatEnum(value) from NoPluralCatsChoice.convert(), then animal and animal_option will correctly contain the enum instance OnlyOneCatEnum.CAT and ctx.params will contain the string cat, which is the intended behavior I believe.

The issue is that click.Choice is not expecting convert() to return an instance of an enum. When typer creates a click.Choice under the hood, it passes only with the values of the enum (and the enum is only dealt with in typer):
https://github.com/tiangolo/typer/blob/968d81df54997fa0219ca2de2aeacbab54daa003/typer/main.py#L779-L783

[AlessandroPomponio]

Thank you very much, Brian!
When reading the documentation for custom types on the Click documentation, it gave me the impression that I had to return the correct type already, but I see this is not the case with typer.
Thank you once again so much! ^^