ArgAction::RunFn

[TadoTheMiner]

This ArgAction will make the argument cause a function to be ran and then application exits

[epage]

Could you provide an example signature and a use case? I'm not quite seeing how this is intending to be used. We've found that a large API makes the discovery of features harder which has me interested in exploring how a request like this could help other use cases so we can get more benefit out of the harder discovery cost.

[TadoTheMiner]

In two of my applications (and apparently I have to write it in a third and fourth) I have arguments --print-default-config and --write-default-config. They're currently ArgAction::SetTrue and main function checks if they're set to true, if so, it runs the function and exits. I think it would be cleaner to just have it run a function

[epage]

I can understand the desire and people have been interested in cases like "associate a function with a subcommand". However, I feel like "abort in the middle of parsing, ignoring all future arguments (which is what would happen with an ArgAction)" would be a bit specialized. There would also be the question of what to do for error reporting.