#[derive(ArgEnum)] fails silently on enums with non-unit variants

[epage]

Discussed in #3533

^{Originally posted by Shir0kamii March 4, 2022}
Hi!

I stumbled on a case where the derive implementation of ArgEnum does not produce its impl block without warning. It happens if the enum contains a non-unit variant.

If you try to compile code such as

#[derive(ArgEnum)]
pub enum Test {
    Foo,
    Bar,
    Baz(u16),
}

The derive doesn't produce any code, and errors are later emitted, reporting that Test does not implement ArgEnum. I would consider that as a bug, because it is confusing and unfriendly. It would be better if an error was emitted from the macro.

I think I found the culprit and would be willing to contribute a fix.

However, while browsing similar issues, I found this discussion where one of you proposed then implemented a #[clap(skip)] attribute for skipping variants in ArgEnum implementation. I think that an enum with a skipped non-unit variant should not trigger any error, and instead produce a valid implementation. If you approve of it, I would like to help on that as well.

What do you think?

[Shir0kamii]

This can be closed since #3591 has been merged.