Controller's with CompletableFuture return bad error messages or no error at all

[JamesPeters98]

I can't tell if this is bad API use on my end, as I'm not an expert with Reactor/Async etc.

But my controllers that return a Completable future of a List type e.g

  @QueryMapping
  public CompletableFuture<List<String>> jobNumbers(Instant timestamp, DataFetchingEnvironment env) {
    return CompletableFuture.completedFuture(List.of("123"));
  }

return bad error messages when there are any exceptions outside of the CompletableFuture. In this case, I missed the @Argument annotation on the timestamp parameter but only got this generic message:

n.graphql.execution.ExecutionStrategy    : Can't resolve value (/jobNumbers) : type mismatch error, expected type LIST got class reactor.core.publisher.MonoError

Or if the type is a String it simply just gets passed through to the final query like this:

{
    "data": {
        "jobNumbers": "MonoError"
    }
}

[rstoyanchev]

I could not easily reproduce this. There is something less obvious going on. Could you create a sample through https://start.spring.io/?

[JamesPeters98]

Ah, yes it turns out it seems to only happen when graphql-java-extended-validation is added into the runtime wiring:

 @Bean
  RuntimeWiringConfigurer runtimeWiringConfigurer() {
    var validationRules = ValidationRules.newValidationRules()
      .build();

    return wiring -> {
      wiring.directiveWiring(new ValidationSchemaWiring(validationRules));
    };
  }

I can't tell if this is a Spring issue or GraphQLJava? Or if the configuration is wrong for use with Spring, I've just used the standard directive wiring on the github page.

[JamesPeters98]

Looks like FieldValidatorDataFetcher causes the DataFetcher to bypass ContextDataFetcherDecorator in GraphQlMetricsInstrumentation somewhere.

Not sure if this relates to changes made in, or is similar to, this issue #240

[JamesPeters98]

if (dataFetcher.getClass().getPackage().getName().startsWith("graphql.")) {
    return TraversalControl.CONTINUE;
}

This is where the problem happens in ContextDataFetcherDecorator.java:119

Since FieldValidatorDataFetcher is in the graphql package it doesn't get added as a ContextDataFetcherDecorator

[rstoyanchev]

That does sound like a problem. I'll schedule it to have a closer look. We'll probably have refine how we decide if a DataFetcher should be decorated or not.