Unable to find class for union type

com.coxautodev.graphql.tools.SchemaClassScannerError: Object type 'WeirdPet' is a member of a 
  known union, but no class could be found for that type name.

my schema

union Pet =  NormalPet | WeirdPet

type WeirdPet {
    id: Int
    name: String
    age: Int
    classification: Classification
    availableDate: Date
}

type NormalPet {
    id: Int
    type: Animal
    name: String
    age: Int
    owner: Owner
    availableDate: Date
}

type Query {
    pets: [Pet]
}

Spring boot class

@ComponentScan
@EnableAutoConfiguration
@SpringBootApplication
public class AppGraphql {
    public static void main(String[] args) {
        SpringApplication.run(AppGraphql.class, args);

    }
    @Bean
    public GraphQLSchema schema() {
        return SchemaParser.newParser()
                .files("petshop.graphqls", "Types.graphqls", "InputTypes.graphqls")
                .resolvers(new Query(), new Mutation(), new Subscription(new NewsPublisher()))
                .scalars(new ScalarDate())
                .dictionary("WeirdPet", WeirdPet.class)
                .build().makeExecutableSchema();
    }
}

Found workaround in issue by making sure there's either query request or mutation request defined in schema that returns WeirdPet type

Before :

type Query {
    pets: [Pet]
    owner(id: Int): Owner
    getAdoptablePet: [NormalPet]
    getAdoptableWeirdPet: [NormalPet]
}

type Mutation {
    createPet(name: String, age: Int, type: Animal, owner: OwnerInput) : NormalPet
    addForAdoptPet(name: String, age: Int, type: Animal, availableDate: Date) : NormalPet
}

After

type Query {
    pets: [Pet]
    owner(id: Int): Owner
    getAdoptablePet: [Pet]
    getAdoptableWeirdPet: [WeirdPet]
}

type Mutation {
    createPet(name: String, age: Int, type: Animal, owner: OwnerInput) : NormalPet
    addForAdoptPet(name: String, age: Int, type: Animal, availableDate: Date) : NormalPet
    addForAdoptPet(name: String, age: Int, classification: Classification, availableDate: Date) : WeirdPet
}

I guess we should still able to create union without creating a "request" that returns the specific union type in this case "WeirdPet" type. Is this a bug?

@villerdex
Was facing similar issue and was able to solve by creating a bean of SchemaParserDictionary with union member classes.
With your schema, it would look like:

   @Bean
    public SchemaParserDictionary getSchemaParser() {
        SchemaParserDictionary dictionary = new SchemaParserDictionary();
        dictionary.add(new HashMap() {{
                put("WierdPet", WeirdPet.class);
                put("NormalPet", NormalPet.class);
        }});
        return dictionary;
    }

@villerdex Right now it searches for the types starting at the root resolvers. That could be improved by taking the union definition into account as well.

Same thing seems to happen for interfaces:

"Object type MyType implements a known interface, but no class could be found for that type name. Please pass a class for type MyType in the parser's dictionary."

Any updates on this issue?

Guess not because I got this error on 6.0.1 as well

Same in 7.0.1. I think this is a bug. It only seems to affect you if you happen to use a type in a union for the first time.

No updates yet. We welcome contributions though.

I have a patch that fixes this if someone wants to incorporate it:
discover-union-and-interface-members.patch

Reuse the type match for sealed subclasses and fold their tests

@amimehra

#854 covers the sealed case. If the class behind a union or interface is a Kotlin sealed class or interface, or a Java 17 sealed type, the scanner now uses the subclass named after each member. So no dictionary entries or dummy queries needed:

sealed class Pet {
    data class NormalPet(val name: String) : Pet()
    data class WeirdPet(val classification: String) : Pet()
}

For plain class hierarchies there's no way to list the subclasses of Pet without scanning the classpath, so the dictionary is still the way to go (.dictionary(NormalPet::class.java, WeirdPet::class.java) or a SchemaParserDictionary bean like @amimehra mentioned). The error message already points there.

Closing this. @briankrug's @JsonSubTypes patch is tracked in #862.

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Unable to find class for union type #200

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orvillelim commented on Oct 30, 2018

orvillelim commented on Oct 30, 2018

amimehra commented on Nov 9, 2018

oliemansm commented on Nov 17, 2018

gustavkarlsson commented on Jul 27, 2019

arnabkd commented on Aug 20, 2019

ubarua123 commented on Feb 25, 2020

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