🐛 Ensure an optional argument is shown in brackets, even when metavar is set

[svlandeg]

As stated in the docs, currently when an argument has a default and is thus not required (e.g. tutorial003.py), the help string shows the argument name between brackets when printing the help string:

python tutorial003.py --help
Usage: main.py [OPTIONS] [NAME]
...
Arguments:
[NAME] Who to greet [default: World]

However, when we use metavar to set a synonym for this argument, then suddenly it doesn't appear between brackets anymore, e.g. tutorial006.py

python tutorial006.py --help
Usage: main.py [OPTIONS] ✨username✨

Arguments:
✨username✨ [default: World]

This PR makes that consistent:

python tutorial006.py --help
Usage: main.py [OPTIONS] [✨username✨]

Arguments:
[✨username✨] [default: World]

Follow-up work

I'd love feedback on this, because I'm looking into a few more cases where metavar processing seems to be inconsistent, especially when combined with Rich formatting.

I also have questions around adding the type_var stuff at L394-403 in core.py, and whether that's actually used/documented anywhere in Typer. Those are probably follow-up discussions though, and this PR tries to single out a first fix before moving on.

[Update]: now also created #1410, which I would review after this one.

[github-actions]

📝 Docs preview

Last commit b482a50 at: https://a6d30ef0.typertiangolo.pages.dev

Modified Pages

• https://a6d30ef0.typertiangolo.pages.dev/tutorial/arguments/help/ - (before)

[svlandeg]

Note that this second assert was always redundant, as L18 would already fail if this wasn't the case.

[tiangolo]

Thank you! 🚀

This will be available in Typer 0.20.1, released in the next few hours. 🎉