Increase customizability of values ​​that can be returned by apiReturnType

[matsudamper]

Description

I want to generate the following code

• Need to return CompletableFuture to dispatch DataLoader
• Need to set localContext

DataLoader

fun book(
    id: Long,
    env: DataFetchingEnvironment,
): CompletionStage<DataFetcherResult<Book>> { // here
    val bookNameDataLoader = env.dataLoaderRegistry.getDataLoader<Long, String>("key")
    val bookNameCompletableFuture = bookNameDataLoader.load(id)

    return CompletableFuture.supplyAsync {
        DataFetcherResult.newResult<Book>()
            .localContext("additionalContext")
            .data(
                Book(
                    id = id,
                    name = bookNameCompletableFuture.get(),
                )
            )
            .build()
    }
}

The apiReturnType setting does not seem to allow the following to be output. We would like to enable this.
CompletionStage<DataFetcherResult<T>>

Describe the solution you'd like

I want to enable the following statements

apiReturnType = "java.util.concurrent.CompletionStage<graphql.execution.DataFetcherResult<{{TYPE}}>>"

Describe alternatives you've considered

Other

I can submit the code.
https://github.com/kobylynskyi/graphql-java-codegen/compare/main...matsudamper:graphql-java-codegen:feature/damper/api-return-type-placeholder?expand=1

[kobylynskyi]

@matsudamper your approach looks good to me. But can you please add a few unit tests:

• specifying apiReturnType with {{TYPE}} and checking generated code for APIs that return both type and list of types.
• specifying apiReturnType and apiReturnListType with {{TYPE}} and checking generated code for APIs that return both type and list of types.

[kobylynskyi]

@matsudamper can you please add a few unit tests for the functionality you added? Thank you.

[viacheslav-dobrynin]

Hi, @kobylynskyi, @matsudamper!
Can you please tell me how it should work?
When I add apiReturnType = "java.util.concurrent.CompletableFuture<{{TYPE}}>", this is added for all resolvers.
Although I need only for field resolvers, because for @QueryMapping Spring does not recognize CompletableFuture, only for SchemaMapping (this is necessary for the DataLoader to work properly)

UPD: Spring is not the problem, see details below

[kobylynskyi]

@DobryninVyacheslav in this case I guess we would need to introduce another property, something like fieldResolverReturnType. You would use it instead of apiReturnType

[viacheslav-dobrynin]

Now I tested my code again and found that the problem was not in Spring.
In fact, in the process of testing, I removed the resolver interface, in which there was an annotation @Argument, due to the absence of which nothing worked.
When I returned it, everything worked. I'm sorry I didn't notice this sooner.
However, yes, it would be convenient to have such an option (fieldResolverReturnType)
Thank you!

[viacheslav-dobrynin]

In the end, I came to the conclusion that these settings allow the use of DataLoader and looks like a good solution:

apiReturnType = "reactor.core.publisher.Mono"
apiReturnListType = "reactor.core.publisher.Flux"

For blocking code too. You can use Mono.fromFuture, Flux.fromIterable and so on.
Therefore, for my case, there is no longer a need for the option fieldResolverReturnType, but perhaps it will be useful to someone.