Adding validation for mutually exclusive option groups

[e-g-hategan]

I'm using mutually exclusive option groups as described here
https://ajalt.github.io/clikt/options/#mutually-exclusive-option-groups

but would like to also do parameter validation with validate
https://ajalt.github.io/clikt/parameters/#validate

This doesn't seem to be supported as the returned types are not compatible as far as I can see.

If I'm wrong and this is in fact possible, please provide an example.

[ajalt]

There aren't built-in validate or check extensions for MutuallyExclusiveOptions right now, although you can validate the options in the group individually. Can you share an example of your use case? What are you trying to validate, and what would you want to error message to look like if the validation failed?

The main reason this doesn't exist yet is because I'm not sure if there's a general solution for an error message. For a single option, we print out something like Invalid option --foo: your error message. But with an option group, would we add the names of all options to the message? Just the ones you use? It depends on what the specific error message is, which is why there isn't a built-in for this right now.

[e-g-hategan]

I am only interested in validating the options in the group individually, here's my example:

    sealed class Strategy {
        data class NameBased(val name: String) : Strategy()
        data class IdBased(val id: String) : Strategy()
    }

    private val strategy: Strategy? by mutuallyExclusiveOptions(
        option(
            "--id",
            help = "Name"
        ).convert { Strategy.IdBased(it) }
        // validation required
        ,
        option(
            "--name",
            help = "Id"
        ).convert { Strategy.NameBased(it) }
        // validation required
    ).single()

Are you suggesting I can in fact validate these individually?

My error messages whould be something like "name too long" if over a certain length, similar for id.

[ajalt]

Yes, although you'll need to specify types explicitly, since the mutuallyExclusiveOptions parameters are invariant.

private val strategy: Strategy? by mutuallyExclusiveOptions(
    option("--id", help = "Name")
        .convert<String, Strategy> { Strategy.IdBased(it) }
        .check { (it as Strategy.IdBased).id.isNotEmpty() },
    option("--name", help = "Id")
        .convert<String, Strategy> { Strategy.NameBased(it) }
        .validate { require((it as Strategy.NameBased).name.isNotEmpty()) { "name too short" } }
).single()

[ajalt]

Ok, I made the parameters covariant in #267, so with that change you'll be able to validate individual options without explicitly specifying the types. Let me know if that solves your problem.