Handling exceptions in case when we want to use VirtualThreadTaskExecutor

[l3r8yJ]

So, guys, I've been using this configuration to enable the virtual threads feature:

@Bean
fun dgsAsyncTaskExecutor(contextRegistry: ContextRegistry): AsyncTaskExecutor {
    log.info("Enabling virtual threads for DGS")
    val contextSnapshotFactory = ContextSnapshotFactory.builder().contextRegistry(contextRegistry).build()
    return DelegatingSecurityContextAsyncTaskExecutor(VirtualThreadTaskExecutor(contextSnapshotFactory))
}

However, this causes the following problem: If an exception is thrown in a virtual thread task, for example, when a client lacks the necessary permissions, they should see an Access Denied message due to the AccessDeniedException. Instead, they receive an InvocationTargetException. To resolve this in my project, I used the following code:

/**
 * Handles invocation target exceptions, as we are using the virtual threads executor,
 * which wraps every exception in an `InvocationTargetException`.
 */
@Bean
fun invocationTargetExceptionHandler(): DataFetcherExceptionHandler =
    object : DefaultDataFetcherExceptionHandler() {
        override fun handleException(handlerParameters: DataFetcherExceptionHandlerParameters) =
            DataFetcherExceptionHandlerParameters.newExceptionParameters()
                .exception(unwrapCompletionException(handlerParameters.exception))
                .dataFetchingEnvironment(handlerParameters.dataFetchingEnvironment)
                .build()
                .let { super.handleException(it) }
    }

private fun unwrapCompletionException(e: Throwable): Throwable {
    return when (e) {
        is CompletionException -> unwrapCompletionException(e.cause ?: e)
        is InvocationTargetException -> unwrapCompletionException(e.targetException)
        else -> e
    }
}

This code essentially does the same thing as DefaultDataFetcherExceptionHandler, so I think it would be a good idea to modify method, unwrapCompletionException in DefaultDataFetcherExceptionHandler to support this exception handling.

[l3r8yJ]

linking the PR #2133

[l3r8yJ]

@paulbakker take a look, please

[l3r8yJ]

closed in #2133