bug: Variadic list typer.Argument with default value broken between 0.25 and 0.26

[tchervychek]

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 documentation, with the integrated search.
• I already searched in Google "How to X" and didn't find any information.
• I already read and followed all the tutorials in the docs and didn't find an answer.

Example Code

from typing import Annotated

import typer

app = typer.Typer()


@app.command()
def run(
    tests: Annotated[list[str], typer.Argument()] = ["foo"],
) -> None:
    print(tests)


def main():
    app()


if __name__ == "__main__":
    main()

Description

See the repro.

Argument tests has a default value. The default value is not respected in Typer 0.26

$ uv run --quiet --with typer==0.25.0 -- python repro.py
['foo']

versus

$ uv run --quiet --with typer==0.26.0 -- python repro.py
[]

I could not find any documentation stating that this behaviour is not supported or that this is a breaking change going from 0.25 to 0.26.

Operating System

Linux

Operating System Details

Ubuntu 24.04 (running in WSL)

Project Version

0.26.4

Python Version

Python 3.12.3

Additional Context

No response

[svlandeg]

That looks like a potential bug. Thanks for the report, I'll look into it!

[svlandeg]

Confirmed that this is a bug, I'll push a fix later today!

[tchervychek]

Thanks!

[svlandeg]

PR: #1821

Released in Typer 0.26.6 🎉