awscli-like options that are shared across subcommands

[seanmcl]

The aws cli lets you do stuff like

aws --profile foo --region us-west-2 s3api get-bucket-policy --bucket foo

where there are 200 subcommands, but --profile and --region are shared across all of them. I know I can get close to this by creating opts for profile and region and just share them across all my subcommands. I don't love this solution though. Apart from all the code copying, they only show up in the help for the subcommand, but not the help for the top command. I was hoping there's a way to structure the cli like

foo
  options for all subcommands of foo
  bar1
    options for bar1
  bar2
    options for bar2
  ...

Is this kind of thing possible today in Decline?

[bkirwi]

It is! I'm not able to respond in much detail now, but effectively doing something like `(profileOpt, regionOpt, subcommand1 orElse subcommand2).mapN(...)` works and has the behaviour you desire.

[bkirwi]

To elaborate a bit more: Opts.subcommand is an Opts instance like any other, and can be combined in all the usual ways. It's often used with orElse, but using product/mapN and friends works just as well when you want a subcommand and some other options.

One final wrinkle to know about is that if you're using the "effect style", you'll generally end up with all your subcommands having a function type. One pattern some folks like is to come up with a special subcommand trait:

trait Subcommand {
  def run(profile: Profile, ...): IO[Unit]
}

val fooCommand: Opts[Subcommand] = ???
val profileOpt: Opts[Profile] = ???
(profileOpt, fooCommand).mapN((profile, sub) => sub.run(profile))

[seanmcl]

Thank you so much for your reply. Appreciate your time!