Resteasy reactive: No proper handling of missing or empty @Produces for Multi results

[michalszynkiewicz]

more info: https://quarkusio.zulipchat.com/#narrow/stream/187030-users/topic/html.20web.20requests/near/229859196

Describe the bug
A rest endpoint returning a multi, missing a @Produces annotation results in NullPointerException thrown at runtime.

java.lang.NullPointerException
at org.jboss.resteasy.reactive.server.handlers.MultiResponseHandler.handle(MultiResponseHandler.java:185)
at org.jboss.resteasy.reactive.server.handlers.MultiResponseHandler.handle(MultiResponseHandler.java:16)
at org.jboss.resteasy.reactive.common.core.AbstractResteasyReactiveContext.run(AbstractResteasyReactiveContext.java:117)
at org.jboss.resteasy.reactive.server.handlers.RestInitialHandler.beginProcessing(RestInitialHandler.java:47)
at org.jboss.resteasy.reactive.server.vertx.ResteasyReactiveVertxHandler.handle(ResteasyReactiveVertxHandler.java:17)
at org.jboss.resteasy.reactive.server.vertx.ResteasyReactiveVertxHandler.handle(ResteasyReactiveVertxHandler.java:7)
at io.vertx.ext.web.impl.RouteState.handleContext(RouteState.java:1038)
at io.vertx.ext.web.impl.RoutingContextImplBase.iterateNext(RoutingContextImplBase.java:137)
at io.vertx.ext.web.impl.RoutingContextImpl.next(RoutingContextImpl.java:132)
at io.quarkus.vertx.http.runtime.StaticResourcesRecorder.lambda$start$1(StaticResourcesRecorder.java:62)
at io.vertx.ext.web.impl.RouteState.handleContext(RouteState.java:1038)
at io.vertx.ext.web.impl.RoutingContextImplBase.iterateNext(RoutingContextImplBase.java:101)
at io.vertx.ext.web.impl.RoutingContextImpl.next(RoutingContextImpl.java:132)

Adding the annotation without value produces a different NPE:

java.lang.RuntimeException: java.lang.RuntimeException: Failed to process method org.acme.GreetingResource#io.smallrye.mutiny.Multi<java.util.Map> check(java.lang.String url)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.createEndpoints(EndpointIndexer.java:235)
at io.quarkus.resteasy.reactive.server.deployment.ResteasyReactiveProcessor.setupEndpoints(ResteasyReactiveProcessor.java:388)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at io.quarkus.deployment.ExtensionLoader$2.execute(ExtensionLoader.java:920)
at io.quarkus.builder.BuildContext.run(BuildContext.java:277)
at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2415)
at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1452)
at java.base/java.lang.Thread.run(Thread.java:834)
at org.jboss.threads.JBossThread.run(JBossThread.java:501)
Caused by: java.lang.RuntimeException: Failed to process method org.acme.GreetingResource#io.smallrye.mutiny.Multi<java.util.Map> check(java.lang.String url)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.createResourceMethod(EndpointIndexer.java:506)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.createEndpoints(EndpointIndexer.java:276)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.createEndpoints(EndpointIndexer.java:206)
... 11 more
Caused by: java.lang.NullPointerException
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.extractProducesConsumesValues(EndpointIndexer.java:622)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.extractProducesConsumesValues(EndpointIndexer.java:611)
at org.jboss.resteasy.reactive.common.processor.EndpointIndexer.createResourceMethod(EndpointIndexer.java:463)
... 13 more

at io.quarkus.runner.bootstrap.AugmentActionImpl.runAugment(AugmentActionImpl.java:308)
at io.quarkus.runner.bootstrap.AugmentActionImpl.reloadExistingApplication(AugmentActionImpl.java:195)

Expected behavior
Build error

Actual behavior
(Describe the actual behavior clearly and concisely.)

To Reproduce

https://github.com/thomaswue/quarkus-example/blob/4bd0ee66405d26ab7d0bdc36593db68404218324/src/main/java/org/acme/GreetingResource.java

[quarkus-bot]

/cc @FroMage, @geoand, @stuartwdouglas

[geoand]

Thanks for reporting this.

We definitely need to do something more user friendly