CLI Option prompts with default=None don't default to None

[Patrick Armengol]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the Typer documentation, with the integrated search.
• I already searched in Google "How to X in Typer" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to Typer but to Click.

Commit to Help

• I commit to help with one of those options 👆

Example Code

from typing import Optional

import typer

app = typer.Typer()


@app.command()
def foo(
    boo: Optional[int] = typer.Option(default=42, prompt=True),
    too: Optional[int] = typer.Option(default=None, prompt=True),
    moo: Optional[int] = typer.Option(default=None)
) -> None:
    print(f'\nresult\n{boo}\n{too}\n{moo}')


if __name__ == '__main__':
    app()

Description

When defining an CLI Option prompt, if the default is set to None, the prompt requires an answer, and the answer needs to be of the non-None-type defined for the parameter.

Here's the output to the example code:

Boo [42]: 
Too: 
Too: asdf
Error: 'asdf' is not a valid integer.
Too: 3

result
42
3
None

42 is recognized as the default for boo, so when hitting return boo is set to 42.
But too does not display "None" as the default, and requires an answer of type int.
This is in contrast with both boo and moo, which revert to the defaults correctly when no input is given.
What I expect to happen is that too is set to None when no input is given in the prompt.

Perhaps I am missing something. Anyone have any ideas how to get around this using the built in Typer prompt?

If this is currently a limitation of prompting, I would like to request an enhancement to allow None to be used as a default.

Operating System

Linux

Operating System Details

No response

Typer Version

0.7.0

Python Version

3.10.8

Additional Context

No response

[Patrick Armengol]

Hmm, I initially thought this might not be click related since it deals with types and typer.Option, but now I see it just forwards to extends click.core.Option, which then click's prompt. I'll file again on that project.