Example using clap v3 derive

[thesurlydev]

Could you provide an example of how to integrate with a clap v3 derive app? I'd like to be able to have configuration file and/or environment variables provide defaults, then allow overrides via clap command line args.

[nyurik]

@storyfeet when you have a moment, this would greatly help with getting started! Also, the clap_app! has been deprecated by clap v3, so it is bit confusing how use clap derive. Thx!

[storyfeet]

Hi, Sorry, I don't know why I didn't see this before, I do have a watch on the repo.

I'm looking at the new clap with derive now, and I don't think clap_conf works with it as things stand, It'll take some reading to work out how to make it work.

[nyurik]

Thanks @storyfeet ! You may also be interested in clap-rs/clap#2763 discussion and a more specific clap-rs/clap#1206 issue.

[storyfeet]

The problem working with the derive is the type it creates does not have a general "get" method, instead each required property ie "name" holds an option<T> which is great making sure types are handled correctly,

but clap_conf relies on having a get general mechanism for the Getter Trait which is used to combine the items.

I believe this could also be derived, but if I'm honest I'm in no hurry to start learning to write these kinds of macros. (feel free to have a go) But by the time you've done that, you might as well just use the "builder" as it loses the type information to go back to a string return anyway.

[nyurik]

Update: clap-rs/clap#1206 has just been fixed, so you can iterate over args now.