Allow exception propagation to Swift for Flows

[ubuntudroid]

Right now SKIE doesn't forward errors in Kotlin Flows to Swift.

As per the migration guide:

One real difference between other Coroutines interop solutions and SKIE is that SKIE does not throw exceptions from the underlying Flow. Your Kotlin code will need to deal with exceptions appropriately in its logic rather than expecting that to throw to Swift. Philosophically, this is how we (Touchlab) generally view error handling and KMP. If you’re expecting an error, catch it and make error states an explicit part of the API rather than just letting them bubble up to Swift. However, other developers may not prefer that approach.

I'm a big fan of result wrappers with error state support myself. However, not propagating errors creates a different handling when comparing Swift observers and Kotlin observers which needs to be kept in the back of ones head when developing shared code and also on the receiving end.

Therefore, I would at least make error propagation optional and enable it by default. Developers could then disable it based on a conscious decision.

Having it enabled by default would likely be more what Kotlin developers new to SKIE would expect without reading through the docs (which obviously is still recommended, but I found that taking the position of a complete newcomer usually is a good test for what should be the default for options).

[FilipDolnik]

Thanks for the feature proposal.

For those interested in this feature, you can show your interest by "voting" using the emojis, as some already did, or by leaving a comment.

[DmitriyZaitsev]

I'm also a fan of result wrappers and other monads, but the coroutines have declared a certain type of contract, and I'd like equal adherence to that contract across platforms.