why is not possible to do a `try` inside a @Composable block? ```@Composable override fun build() {...

# compose

[alorma]

why is not possible to do a try inside a @Composable block?

@Composable
override fun build() {
   try {

   }
}

[Grigorii Yurkov]

Composable annotation is not just annotation, it forces compiler to make magic things under the hood. That's like you can't use synchronized block in suspend functions. And I think common ui don't need try catch and if it needs that means you are doing something wrong

[alorma]

well, things crash, like firebase if is not initialized

[alorma]

and I'm doing a library that wrapps firebase...

[Jeremy]

Stuff like that I think want to wrap in a LaunchedTask otherwise it will get executed multiple times

[Jeremy]

You should be able to use try/catch in a LaunchedTask

[jaqxues]

Well you should handle that in a viewmodel. Or have another architecture that tells the ui exactly how to look, without mixing any logic (no try catch) with ui code. That also simplifies the recomposition problem

[alorma]

well yes

[alorma]

but the firebase user will live on a library, so i thougt tha tlibrary can handle itself if firebase auth is loaded or not

[jim]

Long term, we do intend (or at least, would like) to eventually support try-catch blocks. The reason we don't support them yet is primarily due to prioritization of our engineering efforts. Supporting try-catch semantics is a lot of engineering work because the way Compose works with recomposition and parallelization, it is possible that a child is called in situations where the parent isn't on the call stack. But when an exception is thrown, you want the control flow to pass back through the parent, even if the parent was skipped or executed on a different thread. Getting this right requires a decent amount of engineering, and so we had to prioritize other things that were more critical to an initial stable release. Hopefully in a followup release, this can be supported.

[Mark Murphy]

At the risk of asking a silly question... what's the problem with try/catch in a composable? I just tried it, and everything seemed to run correctly. My exception was caught, and the composable still rendered.

I'm not doubting that there is a problem, but, what's the scenario that demonstrates it?

[jim]

To reproduce, attempt calling a composable from within the try-catch block. We disallow that.

[Mark Murphy]

ah, there we go -- thanks!

[Abhishek Bansal]

I got a crash trying to render a large image. It’s not a OOM crash but Canvas: trying to draw too large exception. What is the way to handle such issues apart from reducing image size? because image size may not be in my control all the time.

[Mark Murphy]

I would use something like telephoto.

[Abhishek Bansal]

Right, but unfortunately the crash is coming from inside another library.