Validate all arguments together

[giggio]

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• Searched the closed issues

Describe your use case

I'd like to have a validation function that would validate the arguments together.

Describe the solution you'd like

I'm thinking something like this:

App::new("x")
    .validate(|args| /* some logic and... */ Err(("myarg", "Why invalid"));

(I'm not married to this example, it is just so we can have an idea)

In this case, argument myarg is invalid, after I've gone through some logic that would go through all arguments already supplied (and validated individually).

Alternatives, if applicable

Validate after parsing using ArgMatches.

Additional context

Already discussed at #1913 and #1206, and I think a solution with a closure after on the app context could make sense.

[epage]

Note that in clap3 we added App::error for being able to create custom validation with ArgMatches that looks as if it was from a validator.

#3008 is our other generalization of validation.

Closing this in favor of App::error and #3008. If there is any concern with this, feel free to let us know!

[ctrlcctrlv]

MFEK's fork can do this and was rejected in #3029. If you need a solution right now like we did you could use it. We are waiting for a resolution to #3008 to be able to drop our fork and track upstream again.