Nested type parameters for implementation type cause NullPointerException

[Mobe91]

The following works but is impractical since I need to support multiple response types:

@OpenAPIDefinition
@Path("distances")
public interface DistancesResource {
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    Map<UUID, Map<RouteMetric, Integer>> getDistances();
}

Thus I changed the return type of my resource to Response and used @ApiResponses to designate the possible concrete response types. However, specifying Map<UUID, Map<RouteMetric, Integer>> directly in the annotation is not possible due to the generics involved. Thus I introduced a dummy type for this purpose:

@OpenAPIDefinition
@Path("distances")
public interface DistancesResource {
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @ApiResponses({
            @ApiResponse(responseCode = "200", content = @Content(schema = @Schema(implementation = DistancesResponse.class)))
    })
    Response getDistances();

    abstract class DistancesResponse implements Map<UUID, Map<RouteMetric, Integer>> { }
}

However, resolving the model information now fails with the following exception:

09:15:09,946 ERROR [io.undertow.request] (default task-25) UT005023: Exception handling request to /openapi: java.lang.NullPointerException
	at io.swagger.v3.core.jackson.ModelResolver.resolve(ModelResolver.java:356)
	at io.swagger.v3.core.converter.ModelConverterContextImpl.resolve(ModelConverterContextImpl.java:90)
	at io.swagger.v3.core.converter.ModelConverters.readAllAsResolvedSchema(ModelConverters.java:99)
	at io.swagger.v3.core.util.AnnotationsUtils.getSchema(AnnotationsUtils.java:1054)
	at io.swagger.v3.core.util.AnnotationsUtils.getSchema(AnnotationsUtils.java:1039)
	at io.swagger.v3.core.util.AnnotationsUtils.getContent(AnnotationsUtils.java:995)
	at io.swagger.v3.jaxrs2.OperationParser.getApiResponses(OperationParser.java:76)
	at io.swagger.v3.jaxrs2.Reader.parseMethod(Reader.java:899)
	at io.swagger.v3.jaxrs2.Reader.parseMethod(Reader.java:754)
	at io.swagger.v3.jaxrs2.Reader.read(Reader.java:422)
	at io.swagger.v3.jaxrs2.Reader.read(Reader.java:169)
	at io.swagger.v3.jaxrs2.Reader.read(Reader.java:196)
	at io.swagger.v3.oas.integration.GenericOpenApiContext.read(GenericOpenApiContext.java:353)
	at io.swagger.v3.jaxrs2.integration.OpenApiServlet.doGet(OpenApiServlet.java:49)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
	at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
	at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
	at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
	at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
	at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
	at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
	at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
	at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
	at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
	at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
	at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
	at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
	at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
	at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
	at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:326)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:812)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Workaround

@OpenAPIDefinition
@Path("distances")
public interface DistancesResource {
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @ApiResponses({
            @ApiResponse(responseCode = "200", content = @Content(schema = @Schema(implementation = DistancesResponse.class)))
    })
    Response getDistances();

    @JsonIgnoreProperties("empty")
    abstract class DistancesResponse implements Map<UUID, DistancesResponseEntry > { }

    @JsonIgnoreProperties("empty")
    abstract class DistancesResponseEntry implements Map<RouteMetric, Integer> { }
}

[frantuma]

#2804 fixes the NPE but without full support of scenario in comment above.