Resteasy Reactive: Fix nested bean params for sub resources

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

@@ -0,0 +1,71 @@
+package io.quarkus.resteasy.reactive.server.test.beanparam;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+
+import javax.ws.rs.BeanParam;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.QueryParam;
+import javax.ws.rs.core.MediaType;
+
+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.restassured.RestAssured;
+
+/**
+ * Related to the issue: https://github.com/quarkusio/quarkus/issues/27501
+ */
+public class NestedBeanParamInSubResourcesTest {
+
+    @RegisterExtension
+    static QuarkusUnitTest test = new QuarkusUnitTest()
+            .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
+                    .addClasses(TestResource.class, SearchResource.class, City.class, Country.class));
+
+    @Test
+    void shouldParseNestedBeanParams() {
+        RestAssured.get("/test/city/search?name=Malaga&country=Spain")
+                .then()
+                .statusCode(200)
+                .body(equalTo("Got: Malaga, Spain"));
+    }
+
+    @Path("/test")
+    public static class TestResource {
+
+        @Path("/city")
+        public SearchResource searchCities() {
+            return new SearchResource();
+        }
+
+    }
+
+    public static class SearchResource {
+
+        @GET
+        @Path("/search")
+        @Produces(MediaType.TEXT_PLAIN)
+        public String search(@BeanParam City city) {
+            return "Got: " + city.name + ", " + city.country.country;
+        }
+    }
+
+    public static class City {
+
+        @QueryParam("name")
+        String name;
+
+        @BeanParam
+        Country country;
+    }
+
+    public static class Country {
+        @QueryParam("country")
+        String country;
+    }
+}

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

@@ -350,6 +350,7 @@ public static ResourceScanningResult scanResources(
         Set<String> beanParams = new HashSet<>();
 
         Set<ClassInfo> beanParamAsBeanUsers = new HashSet<>(scannedResources.values());
+        beanParamAsBeanUsers.addAll(possibleSubResources.values());
 
         Collection<AnnotationInstance> unregisteredBeanParamAnnotations = new ArrayList<>(
                 index.getAnnotations(ResteasyReactiveDotNames.BEAN_PARAM));