Websocket errors are not handled

[Sam-Kruglov]

spring-graphql/spring-graphql/src/main/java/org/springframework/graphql/server/webmvc/GraphQlWebSocketHandler.java

Lines 325 to 335 in 29ee6aa

	if (response.getData() instanceof Publisher) {
	// Subscription
	responseFlux = Flux.from((Publisher<ExecutionResult>) response.getData())
	.map(ExecutionResult::toSpecification)
	.doOnSubscribe((subscription) -> {
	Subscription prev = getSessionInfo(session).getSubscriptions().putIfAbsent(id, subscription);
	if (prev != null) {
	throw new SubscriptionExistsException();
	}
	});
	}

ExecutionResult#getErrors can contain errors but it's never checked. My annotated handlers are not invoked.

I work around this by directly reading the data as Flux:

    @Bean
    fun requestErrorLogger() = WebGraphQlInterceptor { request: WebGraphQlRequest, chain: WebGraphQlInterceptor.Chain
        ->
        chain.next(request).map { response ->
            if (response.getData<Any?>() is Publisher<*>) {
                return@map response.transform {
                    it.data(
                        Flux.from(response.getData<Publisher<ExecutionResult>>()!!)
                            .doOnNext { result ->
                                result.errors.forEach { error ->
                                    log.error(...)
                                }
                            }
                    )
                }
            }
            ...

I assume basically any error that can happen will be missed but if you want a specific case, I had this graphql.TypeMismatchError.

That error came from graphq-java when some resolver failed and the execution result/context contained errors here: https://github.com/graphql-java/graphql-java/blob/master/src/main/java/graphql/execution/SubscriptionExecutionStrategy.java#L165