Generate swift CaseIterable for simple enums and errors

[Iskander508]

Identifying enums that conform to the CaseIterable protocol is relatively simple, so we probably can autogenerate the swift protocol conformance code without any risks.

Potentially we could add a new config toggle specifically for this protocol.

[mhammond]

so we probably can autogenerate the swift protocol conformance code without any risks.

I'm interested to know why this wouldn't need a config option whereas, say, Codable does? This isn't to say I think it should, but rather I'm trying to work out where we would draw the line?

[Iskander508]

I'm interested to know why this wouldn't need a config option whereas, say, Codable does? This isn't to say I think it should, but rather I'm trying to work out where we would draw the line?

Yes, why not. I have added a config flag similar to the one about LocalizedError (omit_case_iterable_conformance). Also I have added autogeneration for simple errors, since there it is a similar case.

In general the default conformance autogenerated by swift should not produce anything out-of-ordinary. Similar to the automatic generation of Hashable and Equatable. But for peace of mind it might be better to have a config toggle to remove these if not desired by somebody.

[mhammond]

Thanks, this is great - I like that it's enabled by default rather than opt-in as it seems useful and something we should maybe do in #2490?

I'm mildly confused by the contains_variant_fields rather than object_references checks though?

[mhammond]

nano-nit, please fix this eol

[Iskander508]

It should be OK now

[Iskander508]

I'm mildly confused by the contains_variant_fields rather than object_references checks though?

The CaseIterable protocol can only be autogenerated for enums that don't contain additional fields (not only objects, but even primitive fields). Apple docs
Few examples:

public enum ConnectionEventEnum {
    case dummy
    case connected(deviceAddress: String)
    case disconnected(deviceAddress: String)
}
extension ConnectionEventEnum: CaseIterable {} // ERROR, this will not compile, because some variants contain fields

public enum AnimalEnum {
    case dog
    case cat
}
extension AnimalEnum: CaseIterable {} // OK here, all variants are simple (no additional fields)

[mhammond]

Given the discussion in #2490, we want to default this to off, right? cc @crazytonyli . And any chance of a changelog note for both PRs? :)

[Iskander508]

I have changed the config setting to off-by-default and renamed to generate_case_iterable_conformance (with default false).
And also added points to changelog. Please adjust as needed.

[mhammond]

Sorry for the delay, thank you for your patience!