I have a fairly straightforward use case …

$ myapp config set key some-arbitrary-value

Making subcommands for config and set is no problem. But I would like key to be constrained to a list of valid config fields, and I would like some-arbitrary-value to be completely unconstrained.

Command.ValidArgs apparently applies to all arguments collectively. So in my case, if I set ValidArgs to my list of valid keys, it’ll fail on my arbitrary value.

The best I could come up with is the following approach:

• Create a function that takes an arg position (int) and list of valid values ([]string), and returns a custom PositionalArgs function that validates a single command-line arg against the list. I can use this for the key arg.
• Create a similar function that acts like ArbitraryArgs but only for a single arg. I can use this for the value arg. I think I can skip this step but it’d clearly express my intent, which might be helpful for code readers as well as help/usage text generation.
• Call cobra.MatchAll() with one each of the above PositionalArgs, and assign the result to my command’s Args. This will compose the two positional validations into what I want.

This seems like a fair bit of fussy work for my simple use case. Plus since PositionalArgs functions require a Command object, I’m not sure how I’d easily test my code. I’m happy to consider alternatives to my proposed approach. Otherwise, I’ll forge ahead. Thanks!