SkipModel Observability: support for access(keyPath:) and withMutation(keyPath:_:) ?

[tifroz]

We are working on a skip-tca library to bring a simplified version of The Composable Architecture to our (planned) Skip app. We are planning to open-source it after we are reasonably confident in the code.

We are hitting a roadblock an Android because of the lack of support for access(keyPath:) and withMutation(keyPath:_:) (Without these the runtime can't discriminate between views that need to be re-rendered vs views that can be left alone, which will quickly turns into performance hell, with anything but the simplest state trees).

Happy to get my hands dirty & work on a PR to add support, but I am guessing these method were excluded from the current implementation for a reason...is it reasonable at all for an outsider to work on this?

[dfabulich]

Kotlin doesn't have keypaths.

• Skip Lite has limited support for transpiling keypaths

  • ~ Key paths
    • ✓ As implicit closure parameters
    • ✓ As @Environment keys
    • ✕ Other uses

• I think Skip Fuse can't bridge keypaths at all https://skip.tools/docs/bridging/

  • ✕ Key paths

Neither the transpiler nor the bridge are open-source code. (They're what you pay for when you buy a Skip license.)

[marcprux]

Neither the transpiler nor the bridge are open-source code.

Well, actually…

[aabewhite]

Using Skip Fuse, nothing prevents your Swift code from using key paths. They just can't be bridged to Kotlin code. I guess I'm not clear on the exact requirements?

[tifroz]

Thank you!

For context, the original TCA implementation implements its own flavor of @Observable that relies on withMutation(keyPath:_:) to trigger re-renders and access(keyPath:) for granularity. Without these the automatic re-rendering just doesn't work on Android.

I have been experimenting with some success using a skip-friendly data structure (an @Observable class that acts as a read-only mirror of the state) to get re-renders working in Android. This introduces a meaningful amount of complexity which makes me quite nervous...hopefully this won't turn into bug town !