Generating definition for polymorphic types when only subclass is used

[algattik]

We generate Swagger from JAX-RS/Jackson with polymorphic types, but do not reference the supertype in controllers.

This generates an incorrect OpenAPI type definition, where the discriminator field is missing.

package openapi.test;

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.annotation.JsonTypeName;
import io.swagger.v3.oas.annotations.OpenAPIDefinition;
import jakarta.ws.rs.POST;
import jakarta.ws.rs.Path;

import java.util.ArrayList;
import java.util.List;


@OpenAPIDefinition
@Path("/")
public class PolicyApiController {

    @POST
    public void createPolicy(Policy policy) {
    }

    // @POST
    // public void createRule(Rule policy) {
    // }

    @JsonTypeName("dataspaceconnector:permission")
    public static class Permission extends Rule {
    }

    public static class Policy {

        private final List<Permission> permissions = new ArrayList<>();
        private String target;

        public List<Permission> getPermissions() {
            return permissions;
        }

        public String getTarget() {
            return target;
        }
    }

    @JsonTypeInfo(
            use = JsonTypeInfo.Id.NAME,
            property = "type")
    @JsonSubTypes({
            @JsonSubTypes.Type(value = Permission.class, name = "dataspaceconnector:permission"),
    })
    public static abstract class Rule {

        private String target;

        public String getTarget() {
            return target;
        }

        public void setTarget(String target) {
            this.target = target;
        }
    }
}

Generated YAML definition:

components:
  schemas:
    Permission:
      type: object
      properties:
        target:
          type: string
    Policy:
      type: object
      properties:
        permissions:
          type: array
          items:
            $ref: '#/components/schemas/Permission'
        target:
          type: string

Uncommenting the createRule operation causes what appears to be the correct definition to be generated, as in #2340

components:
  schemas:
    Permission:
      type: object
      allOf:
      - $ref: '#/components/schemas/Rule'
    Policy:
      type: object
      properties:
        permissions:
          type: array
          items:
            $ref: '#/components/schemas/Permission'
        target:
          type: string
    Rule:
      required:
      - type
      type: object
      properties:
        target:
          type: string
        type:
          type: string
      discriminator:
        propertyName: type

Here's the build.gradle.kts file:

val jacksonVersion = "2.13.1"
val swagger = "2.2.0"
val rsApi = "3.1.0"

plugins {
    `java-library`
    id("io.swagger.core.v3.swagger-gradle-plugin") version "2.2.0"
}

repositories {
    mavenCentral()
}

dependencies {
    api("com.fasterxml.jackson.core:jackson-annotations:${jacksonVersion}")
    api("com.fasterxml.jackson.core:jackson-databind:${jacksonVersion}")
    api("jakarta.ws.rs:jakarta.ws.rs-api:${rsApi}")
}


pluginManager.withPlugin("io.swagger.core.v3.swagger-gradle-plugin") {

    dependencies {
        implementation("io.swagger.core.v3:swagger-jaxrs2-jakarta:${swagger}")
        implementation("jakarta.ws.rs:jakarta.ws.rs-api:${rsApi}")
    }
    tasks.withType<io.swagger.v3.plugins.gradle.tasks.ResolveTask> {
        outputFileName = project.name
        outputFormat = io.swagger.v3.plugins.gradle.tasks.ResolveTask.Format.YAML
        prettyPrint = true
        classpath = java.sourceSets["main"].runtimeClasspath
        buildClasspath = classpath
        resourcePackages = setOf("openapi.test")
        outputDir = file("${rootProject.projectDir.path}/resources/openapi/yaml")
    }
    configurations {
        all {
            exclude(group = "com.fasterxml.jackson.jaxrs", module = "jackson-jaxrs-json-provider")
        }
    }
}

[erikpetzold]

We also have this problem.

Here would be an executable example: https://github.com/erikpetzold/swagger-duplicate-schema-generation/blob/main/src/main/java/de/epet/demo/issue1/ignoredparent/SwaggerDemo.java (project contains examples for more issues).

I also found #2863 which says this is intended behaviour.