Provide actionable error message when non-static inner class used as …

…JAX-RS resource

Closes: quarkusio#19757

extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/InnerClassTest.java

@@ -0,0 +1,44 @@
+package io.quarkus.resteasy.reactive.server.test;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.util.function.Supplier;
+
+import javax.enterprise.inject.spi.DeploymentException;
+import javax.ws.rs.Path;
+
+import org.jboss.shrinkwrap.api.ShrinkWrap;
+import org.jboss.shrinkwrap.api.spec.JavaArchive;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.test.QuarkusUnitTest;
+import io.smallrye.common.annotation.Blocking;
+
+public class InnerClassTest {
+
+    @RegisterExtension
+    static QuarkusUnitTest test = new QuarkusUnitTest()
+            .setArchiveProducer(new Supplier<>() {
+                @Override
+                public JavaArchive get() {
+                    return ShrinkWrap.create(JavaArchive.class)
+                            .addClasses(Resource.class);
+                }
+            }).setExpectedException(DeploymentException.class);
+
+    @Test
+    public void test() {
+        fail("Should never have been called");
+    }
+
+    @Path("test")
+    public class Resource {
+
+        @Path("hello")
+        @Blocking
+        public String hello() {
+            return "hello";
+        }
+    }
+}

independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/EndpointIndexer.java

@@ -199,6 +199,10 @@ public ResourceClass createEndpoints(ClassInfo classInfo) {
         try {
             String path = scannedResourcePaths.get(classInfo.name());
             ResourceClass clazz = new ResourceClass();
+            if ((classInfo.enclosingClass() != null) && !Modifier.isStatic(classInfo.flags())) {
+                throw new DeploymentException(
+                        "Non static nested resources classes are not supported: '" + classInfo.name() + "'");
+            }
             clazz.setClassName(classInfo.name().toString());
             if (path != null) {
                 if (path.endsWith("/")) {