[BUG] List values get split by character when prompted

Describe the bug

When an option’s type is List[str], the input gets split by character, as it would if I just called list("string")

To Reproduce

Steps to reproduce the behavior with a minimum self-contained file.

Replace each part with your own scenario:

• Create a file main.py with:

import typer

from typing import List

app = typer.Typer()


@app.command()
def main(
    prefix: List[str] = typer.Option(
        ...,
        "-p",
        "--prefix",
        help="Prefix to filter, can specify multiple times",
        prompt="Prefix",
    )
):
    typer.echo(f"{prefix=}")


if __name__ == "__main__":
    app()

• Call it with:

python main.py

• It outputs:

Prefix [()]: abcd qwerty
prefix=('a', 'b', 'c', 'd', ' ', 'q', 'w', 'e', 'r', 't', 'y')

• But I expected it to output:

Prefix [()]: abcd qwerty
prefix=('abcd', 'qwerty')

or

prefix=('abcd qwerty')

• When using multiple flags, it is correct:

python migrate_dcos/test_strings.py -p abcd -p qwerty
prefix=('abcd', 'qwerty')

Expected behavior

I expected the values to be automatically (or with an Option argument) split on spaces, rather than the single string getting cast to a tuple.

Environment

• OS: macOS
• Typer Version: 0.1.0
• Python version: Python 3.8.1

Additional context

I can work around it for space and comma-delimited values with:

def fix_strlist_value(value):
    if " " in value or "," in value or all(len(i) == 1 for i in value):
        return [k for k in "".join(value).replace(",", " ").split(" ") if k]
    return value

but I’d rather not have to.

[StephenBrown2]

Yup, sorry, thought that would have happened already.

[poleguy]

This is still a practical problem. Lists of strings are a common thing in python. It seems there are work-arounds in click, but I can’t figure out how to apply them to typer.

I did not find a ticket opened in click for a request to support this.

If someone could suggest how to apply this click fix to typer, I’d be willing to write it up for the official typer documentation:

https://stackoverflow.com/questions/47631914/how-to-pass-several-list-of-arguments-to-click-option