When an exception (field error) happens during resolution of a field, completeValue is called with a null resolvedValue. If the field is a GraphQLNonNull, that leads to a GraphQLException being thrown which is never caught.
According to the GraphQL spec, 6.4.4 Errors and Nullability (http://facebook.github.io/graphql/#sec-Errors-and-Non-Nullability), the null value should be propagated up to the parent field in this case (and if that is non-nullable, up again until ultimately a null value under the data key of the response object), without adding additional errors to the result error list.
When an exception (field error) happens during resolution of a field, completeValue is called with a null resolvedValue. If the field is a GraphQLNonNull, that leads to a GraphQLException being thrown which is never caught.
According to the GraphQL spec, 6.4.4 Errors and Nullability (http://facebook.github.io/graphql/#sec-Errors-and-Non-Nullability), the null value should be propagated up to the parent field in this case (and if that is non-nullable, up again until ultimately a null value under the data key of the response object), without adding additional errors to the result error list.