How to regist PageInfo in Schema

[ferrisyang]

Use Relay style for pagination, and write PageInfo type in Schema, will get error [The field type 'PageInfo' is not present] when start the program.
How to regist PageInfo type in Schema?

[ferrisyang]

I found a solution:

@DgsScalar(name = "PageInfo")
public class PageInfoScalar implements Coercing<PageInfo, PageInfo> {

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public PageInfo serialize(Object dataFetcherResult) throws CoercingSerializeException {
        if (dataFetcherResult instanceof PageInfo) {
            return (PageInfo) dataFetcherResult;
        }
        throw new CoercingSerializeException("Not a valid PageInfo");
    }

    @Override
    public PageInfo parseValue(Object input) throws CoercingParseValueException {
       return null;
    }

    @Override
    public PageInfo parseLiteral(Object input) throws CoercingParseLiteralException {
       return null;
    }
}

And in schema, add PageInfo scalar definition:

scalar PageInfo

[srinivasankavitha]

If you want to use it as a scalar type, then sure, but I haven't used or had to use that pattern. It should work without having to declare it as a scalar as well as I had pointed out in the example.

[sbilello]

It does not work without a Scalar registration. Please check this branch to replicate the bug.
sbilello/dgs-examples-java@16f46d5
Thanks
@srinivasankavitha

***************************
APPLICATION FAILED TO START
***************************

Description:

There are problems with the GraphQL Schema:
	 * The field type 'PageInfo' is not present when resolving type 'Show' [@15:1]

[sbilello]

I created this PR https://github.com/Netflix/dgs-examples-java/pull/30/files that shows the problem and how it can work with the current framework.

[amondnet]

@sbilello @ferrisyang
PageInfo is not scalar, you should mapping PageInfo to graphql.relay.PageInfo (source).
https://netflix.github.io/dgs/generating-code-from-schema/#configuring-code-generation

//build.gradle.kts
@OptIn(kotlin.ExperimentalStdlibApi::class)
tasks.withType<com.netflix.graphql.dgs.codegen.gradle.GenerateJavaTask> {
  generateClient = true
  typeMapping = mutableMapOf<String, String>(
    //"JSON" to "graphql.scalars.object.JsonScalar",
    //"Object" to "graphql.scalars.object.ObjectScalar",
    //"Long" to "kotlin.Long",
    "PageInfo" to "graphql.relay.PageInfo",
    "Edge" to "graphql.relay.Edge",
    "Connection" to "graphql.relay.Connection"
  )
}

[sbilello]

@amondnet I solved the problem over here: It looks like that the problem is on defining the schema: Netflix/dgs-examples-java#30 (comment)
Do you think that it can work with just the mapping without specifying the type PageInfo in the schema?

[amondnet]

You should mapping PageInfo to graphql.relay.PageInfo (source).
https://netflix.github.io/dgs/generating-code-from-schema/#configuring-code-generation

//build.gradle.kts
@OptIn(kotlin.ExperimentalStdlibApi::class)
tasks.withType<com.netflix.graphql.dgs.codegen.gradle.GenerateJavaTask> {
  generateClient = true
  typeMapping = mutableMapOf<String, String>(
    //"JSON" to "graphql.scalars.object.JsonScalar",
    //"Object" to "graphql.scalars.object.ObjectScalar",
    //"Long" to "kotlin.Long",
    "PageInfo" to "graphql.relay.PageInfo",
    "Edge" to "graphql.relay.Edge",
    "Connection" to "graphql.relay.Connection"
  )
}