Cannot subclass `User` any more

[DarkDust]

Platform

macOS

Environment

Production

Installed

CocoaPods

Version

8.49.0

Xcode Version

16.2

Did it work on previous versions?

8.41.0

Steps to Reproduce

We have a subclass of Sentry.User with additional informations. Due to the addition of the Codable support in a recent version of the Sentry SDK, this subclass cannot be used any more. The Swift compiler complains:

'required' initializer 'init(from:)' must be provided by subclass of 'User'

However, we cannot provide it, either, since then Swift complains:

initializer 'init(from:)' is declared in extension of 'User' and cannot be overridden

Code to reproduce:

class MyUser: Sentry.User {
	let moreInfo: String
	
	init(userId: String, moreInfo: String) {
		self.moreInfo = moreInfo
		
		super.init(userId: userId)
	}
	
	required init() {
		fatalError("init() has not been implemented")
	}
	
	@available(*, deprecated, message: "…")
	required convenience init(from decoder: any Decoder) throws {
		fatalError("init(from:) has not been implemented")
	}
}

Expected Result

Existing subclass of User should still compile.

Actual Result

We were able to work around this problem by using a convenience initializer, but lost the ability to provide additional informations.

As far as I can see, the only real solution would be to port the whole User class to Swift and have the codable implementation in the main class instead of an extension:

@objc(SentryUser)
class User: NSObject, SentrySerializable, NSCopying, Codable {
   …
}

This way subclasses are able to override the decoding initializer.

Are you willing to submit a PR?

maybe

[philprime]

Hi @DarkDust, thanks for raising this issue.

I do not think that it was intended that SentryUser is to be subclassed, but maybe @philipphofmann can share some insights on that.

Did you try wrap the SentryUser instead of subclassing it?

[DarkDust]

No, I just added a convenience initializer to User and ditched the additional info since it wasn't used right now anyway. So it's not a big deal for us that it cannot be subclassed any more, but it was still surprising since our existing code didn't compile any more after updating the Sentry SDK.

[philprime]

@DarkDust that is of course unintended and unfortunate, as we usually try for that not to happen.

[philipphofmann]

Ahh, sorry, that's an unfortunate side effect of adding Codable via Swift extensions that I totally missed when adding the implementation. @DarkDust, do you have a workaround? We must investigate if we can somehow fix this, but my hopes aren't high.

[DarkDust]

@philipphofmann: I guess the only real solution is to port User to Swift, like this:

@objc(SentryUser)
class User: NSObject, SentrySerializable, NSCopying, Codable {
   …
}

The important part is Codable being part of the class definition, not an extension. This way subclasses are able to override the required initializer of Decodable.

[philipphofmann]

We should be able to fix this by adding extra subclasses for the decodable implementations similar to what we did for SentryEvent

sentry-cocoa/Sources/Sentry/Public/SentryEvent.h

Lines 199 to 217 in 4c5c48c

	/**
	* Subclass of SentryEvent so we can add the Decodable implementation via a Swift extension. We need
	* this due to our mixed use of public Swift and ObjC classes. We could avoid this class by
	* converting SentryReplayEvent back to ObjC, but we rather accept this tradeoff as we want to
	* convert all public classes to Swift in the future. This class needs to be public as we can't add
	* the Decodable extension implementation to a class that is not public.
	*
	* @note: We can’t add the extension for Decodable directly on SentryEvent, because we get an error
	* in SentryReplayEvent: 'required' initializer 'init(from:)' must be provided by subclass of
	* 'Event' Once we add the initializer with required convenience public init(from decoder: any
	* Decoder) throws { fatalError("init(from:) has not been implemented")
	* }
	* we get the error initializer 'init(from:)' is declared in extension of 'Event' and cannot be
	* overridden. Therefore, we add the Decodable implementation not on the Event, but to a subclass of
	* the event.
	*/
	@interface SentryEventDecodable : SentryEvent
	@end

Ideally, we add these classes in Swift and make them internal.