Allow marking options with "deprecated" help or visibility

[grynspan]

Let's say my CLI tool has an old option that's no longer valid:

@Option
public var sendToCzechslovakia = false

Since Czechoslovakia doesn't exist anymore, I've replace it with sendToEuropeanUnion, and I want to inform folks still using it to change their command-line incantations. Wouldn't it be nice if I could write:

@Option(help: .deprecated("Use --send-to-european-union instead"))
public var sendToCzechslovakia = false

And have it automatically be hidden and emit some sort of diagnostic message to stderr?

⚠️ --send-to-czechoslovakia is deprecated: use --send-to-european-union instead

[natecook1000]

This sounds handy, but I don't think there's enough of a consensus around how to display those kinds of messages to implement it as a library feature. You can implement that yourself by:

• providing both flags
• using validate() to print a message if sendToCzechslovakia is true
• using a computed property to make is easy to access sendToEuropeanUnion || sendToCzechslovakia within your command

[rauhul]

how to display those kinds of messages

Seems like we might need a hook for users to decide how to emit the messages. ideally it would be a build time configuration

[grynspan]

I can implement it myself, sure. :)

Was suggesting having a baked-in feature with a (semi-)canonical output might be nice.