Null Default DataFetchers will overwrite non null ones inside RuntimeWiring.Builder

[AntoineGRHD]

Describe the bug

Successive calls to RuntimeWiring.Builder::type will overwrite the defaultDataFetchers value with null if the defaultDataFetcher isn't present.

wiringBuilder.type("Query", builder -> builder.defaultDataFetcher(defaultDataFetcher)) //Sets the default dataFetcher
             .type("Query", builder -> builder.dataFetcher("asset", assetDataFetcher)) //Unsets the default dataFetcher
             .type("Query", builder -> builder.dataFetcher("person", personDataFetcher))

Setting the default data fetcher with the last call will work, but I believe this isn't a good solution since this is a builder pattern and there's already a null check for setting the enumValuesProvider, and typeResolver.

Moreover in my case using it with spring-graphql, Spring's RuntimeWiringConfigurer will first let you set your custom DataFetchers and then add all the annotated data fetchers, not the other way around.

Proposed solution

Inside graphql.schema.idl.RuntimeWiring.class, RuntimeWiring.Builder::type(TypeRuntimeWiring typeRuntimeWiring)

Replace :

this.defaultDataFetchers.put(typeName, typeRuntimeWiring.getDefaultDataFetcher());

With : (Just like the typeResolver and enumValuesProvider right after that)

DataFetcher defaultDataFetcher = typeRuntimeWiring.getDefaultDataFetcher();
if (defaultDataFetcher != null) {
        this.defaultDataFetchers.put(typeName, defaultDataFetcher);
}

[bbakerman]

Why is that you calling a TypeRuntimeWiring.Builder so many times? Is this trying to show that multiple steps might continue to add more config into an existing type?

eg your example

wiringBuilder.type("Query", builder -> builder.defaultDataFetcher(defaultDataFetcher)) //Sets the default dataFetcher
             .type("Query", builder -> builder.dataFetcher("asset", assetDataFetcher)) //Unsets the default dataFetcher
             .type("Query", builder -> builder.dataFetcher("person", personDataFetcher))

versus

wiringBuilder.type("Query", builder -> builder
    .defaultDataFetcher(defaultDataFetcher)
    .dataFetcher("asset", assetDataFetcher)
    .dataFetcher("person", personDataFetcher)
)

??

I can look into this

[AntoineGRHD]

Thanks for working on this issue.

Concerning your question, you're absolutely right.
The RuntimeWiring.Builder is used by multiple beans in spring-graphql (through the RuntimeWiringConfigurer), each bean call type(). I wanted to convey that idea in my example.
I wouldn't do repeated calls to type() in the same method