Hi there,

I have noticed that if a DataFetcher returns a CompletableFuture, and this CompletableFuture completes exceptionally with GraphQLError as an exception, then the extensions on this GraphQLError are nor rendered to the response.

The reason is that ExecutionStrategy.handleFetchingExcetion() just delegates to

parameters.deferredErrorSupport().onFetchingException(parameters, e);

and it is never checked that the supplied Throwable may implement GraphQLError. This means that the async code can not append any custom extensions to the errors.

This happens in graphql-java 8.0