Option(...) make options as required but not working

[magarage]

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Example Code

import typer
from typer import (
    Option
)

def main(
    opt1: str = Option(...)	# required option
):
	# must not be printed as None but print None
    print(opt1)

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

Description

(I’m not a native English speaker, so please excuse any awkward phrasing.)

I tested this with Typer 0.17.4, and I noticed that neither Option() nor Option(...) seems to make an option behave as truly required.

When I tested the same behavior with Click, it worked as expected. Looking into how Typer and Click handle this internally, I found the following:

In Click, an option raises a MissingParameter exception only if it is both required and its value is UNSET:

# raise MissingParameter when required and value == UNSET
if self.required and self.value_is_missing(value):
    raise MissingParameter(ctx=ctx, param=self)

According to Typer’s documentation, using ellipsis (...) as the default should make an option required.

However, when using ellipsis, because of the logic in Typer’s get_click_param function in main.py:
• required is set to True,
• but default becomes None instead of UNSET.

As a result, the Click condition above is never satisfied.

If I try forcing it with Option(UNSET):
• the default is indeed UNSET,
• but since it is no longer ellipsis, required is set to False.

Operating System

macOS

Operating System Details

No response

Typer Version

0.17.4

Python Version

3.10.12

Additional Context

No response

[acmiyaguchi]

I think you're probably running into the same issue over here #1334

[svlandeg]

This is now fixed and released:

• Typer 0.17.5 restricts Click to below 8.3.0 (as a quick fix)
• Typer 0.18.0 allows Click 8.3.0 and fixes this bug