What is the recommended way to handle errors happe...

# compose

[Per Jansson]

What is the recommended way to handle errors happening inside composables, i.e. the corresponding way that React handles it with ErrorBoundary? We are using a third-party library providing us a composasble, but when that sometimes errors out the whole applications crashes. I would be nice to be able to try/catch this, but that does not compile: “Try catch is not supported around composable function invocations”.

Example:

@Composable
fun MyApp() {
  ..
  ..
  ThirdPartyComposableThatSometimesErrorsOut() {
    ...
  }
}

I can’t do

@Composable
fun MyApp() {
  ..
  ..
  try {
    ThirdPartyComposableThatSometimesErrorsOut() {
      ...
    }
  } catch (error: Throwable) {
    // Handle the error here
  }
}

[mgrazianodecastro]

This one looks hard, I don't have a runtime broken composable to test 😅, but I've tried this:

sealed class MyErrorHandler {
    data class Ok(val content: @Composable () -> Unit): MyErrorHandler()
    object Err: MyErrorHandler()
}

fun getMyThirdPartyComposable(): MyErrorHandler {
        return try {
            MyErrorHandler.Ok {
                ComposeView(this).apply {  // get the context from somewhere
                    setContent {
                        Text(text = "Hello world.")
                    }
                }
            }

        }catch (err: Exception){
            MyErrorHandler.Err
        }
    }
}

[mgrazianodecastro]

then we would match inside the composable tree. I'm curious to see the result!

[Per Jansson]

I might be doing something wrong but:

1. When I’m using it to compose the 3rd party composable that errors out, it still returns MyErrorHandler.Ok
2. When I’m using it to compose the 3rd party composable when it works, it returns MyErrorHandler.Ok but does not compose anything on the screen.
I’m passing in LocalContext.current as context and rendering the response from getMyThirdPartyComposable with something like this:

@Composable
fun MyView() {
    val context = LocalContext.current
    val errorHandler = getMyThirdPartyComposable(context)

    when (errorHandler) {
        is MyErrorHandler.Ok -> {
            errorHandler.content()
        }
        is MyErrorHandler.Err -> {
            // handle the error
        }
    }
}