Is try/catch supported in `@Composables` now? I tr...

# compose

[mbonnin]

Is try/catch supported in @Composables now? I tried using runCatching and I got a weird error where the result was interpreted as a T (and not a Result<T>, see screenshot the debugger sees two types for the same lvalue ?!?). I ended up using try/catch and now it's all working but searching the backlog of this channel (https://kotlinlang.slack.com/archives/CJLTWPH7S/p1603737209131700), it looks like this might be dangerous?

[jim]

It is safe to catch exceptions in a composable function, but not safe for a composable function to throw an exception. The compiler will usually give you an error if you try to wrap a composable function in a try-catch block because it indicates that you might have been expecting that the composable might throw.

[mbonnin]

Well then I'm definitely in a weird spot... Is there a reason runCatching would behave differently as try/catch ?

[jim]

Because the compiler doesn't know that runCatching catches exceptions.

[mbonnin]

Ah

[mbonnin]

But still, it should expect a Result<T> ?

[mbonnin]

Looks like the compiler has "forced unwrapped" the Result but the downstream code doesn't know it or something like this

[jim]

I wouldn't expect the type to be impacted, please file a bug with a minimal repro.

[mbonnin]

(Fwiw it's compose desktop, not sure if it changes something)

[jim]

That should not change anything, but the bug should be filed against upstream Compose (https://issuetracker.google.com/issues?q=componentid:612128) as failures in the type system would not be a desktop-specific issue.

[mbonnin]

Filed there https://issuetracker.google.com/issues/182693597

[jim]

👍 Thanks!