Result.map {} can cause a ClassCastException if an exception that isn't of the right type is thrown inside it

[Benjozork]

It would be useful to add a function, let's say for example mapSafe that could handle an exception of another type, for example:

suspend fun <V : Any, U : Any, E : Exception, D : Exception> SuspendableResult<V, E>.mapSafe(transform: suspend (V) -> U): SuspendableResult<U, D> = try {
    when (this) {
        is SuspendableResult.Success -> SuspendableResult.Success(transform(value))
        is SuspendableResult.Failure -> SuspendableResult.Failure(error)
    }
} catch (ex: Exception) {
    SuspendableResult.error(ex as D)
}

Haven't tested this. Thoughts ?

[krzykrucz]

This happens in case of Result as well. It would be better not to handle these exceptions at all. Because ClassCastException in the least expected moment at runtime is not a good thing, in my opinion.

What do you think @kittinunf ?

[kittinunf]

To be honest, I am reluctant to add this functionality. Do you think you can have a top-level exception that every other error conforms too and use that one instead?

[R4md4c]

Hope PR #74 gets merged and release soon as we've been suffering from this crash in production.

I think it's more reproducible when dealing with coroutines where sometimes a CancellationException is thrown due to the CoroutineScope of the current suspend method gets cancelled, and since in the mapError we're expecting our custom domain exception class it crashes instead due to ClassCastException.

Example:

remoteDataSource.retrieveFromDataSource() // Returns a SuspendableResult<Data, DataSourceException> 
    .mapError { exception: DataSourceException  ->   } // Crashes here because a JobCancellationException was thrown but we're expecting a DataSourceException

[kittinunf]

It has been merged quite some time ago! Please report it back whether it solves the problem or not.