Having a hard time manually implementing a TypedValueParser with proper error handling

[fmease]

Hey,
I have an already existing parsing function defined in a separate crate which I want to use to implement a TypedValueParser.
The main reason for this is to be able to emit clap errors to have a consistent style for CLI errors. I'd really like clap to emit sth. akin to error: "source" isn't a valid value for '--sth <VALUE>' (which is nicely integrated e.g. by being colored).

Unfortunately, I am facing difficulties with passing along the error info and the context.
When I construct a raw error with Error::raw(kind, message), the error isn't colored and there is no context / info (I mean the for '--sth <VALUE>' part). Error::raw recommends using Command::error (to pass along that metadata), however it takes a &mut Command while I only have access to a &Command inside TypedValueParser::parse{,_ref}.
There is no way for me to set the error info / context.
I've checked the implementations of StringValueParser and BoolValueParser to try to learn how one is supposed to do it.
Alas they through and through rely on private functionality like Error::{invalid_value, set_info}.

Is the API still in development or is there a concise way to integrate nicely with clap's error system?

[epage]

Sorry I had somehow overlooked this. #4140 is a similar discussion.

I would first ask if you need a custom TypedValueParser for what you are wanting or

• If your type implements FromStr, then you can use value_parser! to get one for free (automatically done in the derive API)
• Provide a Fn(&str) -> Result<T, E> to value_parser and as the function is a TypedValueParser.

These will take your existing error and wrap it in all of the clap error features. If what you are wanting is even more control over the error, than yes, that would required a TypedValueParser and is being discussed in #4362