Version 0.19.1 breaks default_factory that returns empty list

[KiSchnelle]

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.
• I already searched in Google "How to X in Typer" and didn't find any information.
• I already read and followed all the tutorials 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 dataclasses import dataclass from typing import Annotated import typer app = typer.Typer() def default_classes() -> list[str]: return [] @app.command() @dataclass class TestCommandd: classes: Annotated[ list[str], typer.Option( default_factory=default_classes, help="List of classes.", rich_help_panel="Options", show_default=False, ), ] def __post_init__(self) -> None: print(self.classes) if __name__ == "__main__": app()

Description

Hi,

I found a for me quite breaking change, probably cause I use it a bit unconventional:D
Probably this pull was the reason.
#1018

In typer version 0.19.0 this returns [] as wanted. In version 0.19.1 this returns the function instead.
I know it's probably not the best way to use like this but I would say it's kind of a breaking change. Anyway if the new way is wanted it should be documented in release notes maybe.

cheers
Kilian

Operating System

Linux

Operating System Details

No response

Typer Version

0.19.0 and 0.19.1

Python Version

3.13.5

Additional Context

No response

[YuriiMotov]

The same without dataclass:

from typing import Annotated import typer app = typer.Typer() def default_classes() -> list[str]: return [] @app.command() def cmd( classes: Annotated[ list[str], typer.Option( default_factory=default_classes, ), ] ): print(classes) # <function default_classes at 0x736d4dfba340> if __name__ == "__main__": app()

[svlandeg]

Thanks for the report! You're right that this broke accidentally in PR #1018 - I'll be looking into it.

[svlandeg]

PR with some additional background & analysis, and a fix for this regression: #1350

[KiSchnelle]

that should cover it, thanks a lot!

[svlandeg]

The fix is now released as 0.19.2. Thanks again for the report! 🙏