Reactive routes - fail if void method and no param can end the response

- resolves #15470

extensions/vertx-web/deployment/src/main/java/io/quarkus/vertx/web/deployment/VertxWebProcessor.java

@@ -477,6 +477,7 @@ private void validateRouteMethod(BeanInfo bean, MethodInfo method,
                                 "Route business method returning a Uni/Multi must have a generic parameter [method: %s, bean: %s]",
                                 method, bean));
             }
+            boolean canEndResponse = false;
             int idx = 0;
             int failureParams = 0;
             for (Type paramType : params) {
@@ -507,12 +508,22 @@ private void validateRouteMethod(BeanInfo bean, MethodInfo method,
                 // A param injector may validate the parameter annotations
                 injector.validate(bean, method, routeAnnotation, paramType, paramAnnotations);
 
+                if (injector.canEndResponse) {
+                    canEndResponse = true;
+                }
+
                 if (Route.HandlerType.FAILURE == handlerType && isThrowable(paramType, index)) {
                     failureParams++;
                 }
                 idx++;
             }
 
+            if (method.returnType().kind() == Kind.VOID && !canEndResponse) {
+                throw new IllegalStateException(String.format(
+                        "Route method that returns void must accept at least one parameter that can end the response [method: %s, bean: %s]",
+                        method, bean));
+            }
+
             if (failureParams > 1) {
                 throw new IllegalStateException(String.format(
                         "A failure handler may only define one failure parameter - route method %s declared on %s",
@@ -1131,17 +1142,18 @@ private List<ParameterInjector> getMatchingInjectors(Type paramType, Set<Annotat
     static List<ParameterInjector> initParamInjectors() {
         List<ParameterInjector> injectors = new ArrayList<>();
 
-        injectors.add(ParameterInjector.builder().matchType(io.quarkus.vertx.web.deployment.DotNames.ROUTING_CONTEXT)
-                .resultHandleProvider(new ResultHandleProvider() {
-                    @Override
-                    public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
-                            ResultHandle routingContext, MethodCreator invoke, int position,
-                            BuildProducer<ReflectiveHierarchyBuildItem> reflectiveHierarchy) {
-                        return routingContext;
-                    }
-                }).build());
+        injectors.add(
+                ParameterInjector.builder().canEndResponse().matchType(io.quarkus.vertx.web.deployment.DotNames.ROUTING_CONTEXT)
+                        .resultHandleProvider(new ResultHandleProvider() {
+                            @Override
+                            public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
+                                    ResultHandle routingContext, MethodCreator invoke, int position,
+                                    BuildProducer<ReflectiveHierarchyBuildItem> reflectiveHierarchy) {
+                                return routingContext;
+                            }
+                        }).build());
 
-        injectors.add(ParameterInjector.builder().matchType(DotNames.ROUTING_EXCHANGE)
+        injectors.add(ParameterInjector.builder().canEndResponse().matchType(DotNames.ROUTING_EXCHANGE)
                 .resultHandleProvider(new ResultHandleProvider() {
                     @Override
                     public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
@@ -1154,7 +1166,7 @@ public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstanc
                     }
                 }).build());
 
-        injectors.add(ParameterInjector.builder().matchType(DotNames.HTTP_SERVER_REQUEST)
+        injectors.add(ParameterInjector.builder().canEndResponse().matchType(DotNames.HTTP_SERVER_REQUEST)
                 .resultHandleProvider(new ResultHandleProvider() {
                     @Override
                     public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
@@ -1166,7 +1178,7 @@ public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstanc
                     }
                 }).build());
 
-        injectors.add(ParameterInjector.builder().matchType(DotNames.HTTP_SERVER_RESPONSE)
+        injectors.add(ParameterInjector.builder().canEndResponse().matchType(DotNames.HTTP_SERVER_RESPONSE)
                 .resultHandleProvider(new ResultHandleProvider() {
                     @Override
                     public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
@@ -1178,7 +1190,7 @@ public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstanc
                     }
                 }).build());
 
-        injectors.add(ParameterInjector.builder().matchType(DotNames.MUTINY_HTTP_SERVER_REQUEST)
+        injectors.add(ParameterInjector.builder().canEndResponse().matchType(DotNames.MUTINY_HTTP_SERVER_REQUEST)
                 .resultHandleProvider(new ResultHandleProvider() {
                     @Override
                     public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstance> annotations,
@@ -1195,7 +1207,7 @@ public ResultHandle get(MethodInfo method, Type paramType, Set<AnnotationInstanc
                 }).build());
 
         injectors
-                .add(ParameterInjector.builder().matchType(DotNames.MUTINY_HTTP_SERVER_RESPONSE)
+                .add(ParameterInjector.builder().canEndResponse().matchType(DotNames.MUTINY_HTTP_SERVER_RESPONSE)
                         .resultHandleProvider(new ResultHandleProvider() {
                             @Override
                             public ResultHandle get(MethodInfo method, Type paramType,
@@ -1429,6 +1441,7 @@ static Builder builder() {
         final ResultHandleProvider provider;
         final Route.HandlerType targetHandlerType;
         final ParamValidator validator;
+        final boolean canEndResponse;
 
         ParameterInjector(ParameterInjector.Builder builder) {
             if (builder.predicate != null) {
@@ -1494,6 +1507,7 @@ public boolean test(Type paramType, Set<AnnotationInstance> paramAnnotations, In
             this.provider = builder.provider;
             this.targetHandlerType = builder.targetHandlerType;
             this.validator = builder.validator;
+            this.canEndResponse = builder.canEndResponse;
         }
 
         boolean matches(Type paramType, Set<AnnotationInstance> paramAnnotations, IndexView index) {
@@ -1527,6 +1541,7 @@ static class Builder {
             ResultHandleProvider provider;
             Route.HandlerType targetHandlerType;
             ParamValidator validator;
+            boolean canEndResponse;
 
             Builder matchType(DotName className) {
                 return matchType(Type.create(className, Kind.CLASS));
@@ -1609,6 +1624,11 @@ Builder validate(ParamValidator validator) {
                 return this;
             }
 
+            Builder canEndResponse() {
+                this.canEndResponse = true;
+                return this;
+            }
+
             ParameterInjector build() {
                 return new ParameterInjector(this);
             }

extensions/vertx-web/deployment/src/test/java/io/quarkus/vertx/web/failure/FailureHandlerPathTest.java

@@ -29,7 +29,7 @@ public void test() {
     public static class Routes {
 
         @Route
-        void fail(@Param String type) {
+        String fail(@Param String type) {
             throw new RuntimeException("Unknown!");
         }
 

extensions/vertx-web/deployment/src/test/java/io/quarkus/vertx/web/failure/FailureHandlerTest.java

@@ -30,7 +30,7 @@ public void test() {
     public static class Routes {
 
         @Route
-        void fail(@Param String type) {
+        String fail(@Param String type) {
             if ("unsupported".equals(type)) {
                 throw new UnsupportedOperationException("Unsupported!");
             } else {

extensions/vertx-web/deployment/src/test/java/io/quarkus/vertx/web/params/VoidInvalidParameterTest.java

@@ -0,0 +1,36 @@
+package io.quarkus.vertx.web.params;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+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.quarkus.vertx.web.Param;
+import io.quarkus.vertx.web.Route;
+
+public class VoidInvalidParameterTest {
+
+    @RegisterExtension
+    static final QuarkusUnitTest config = new QuarkusUnitTest()
+            .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
+                    .addClasses(SimpleBean.class))
+            .setExpectedException(IllegalStateException.class);
+
+    @Test
+    public void testValidationFailed() {
+        fail();
+    }
+
+    static class SimpleBean {
+
+        @Route
+        void hello(@Param("myParam") String param) {
+            // This route is illegal - it's not possible to end the response
+        }
+
+    }
+
+}

extensions/vertx-web/runtime/src/main/java/io/quarkus/vertx/web/Route.java

@@ -67,7 +67,8 @@
  *  </code>
  * </pre>
  * 
- * If the annotated method returns {@code void} then it has to accept at least one argument.
+ * If the annotated method returns {@code void} then it has to accept at least one argument that makes it possible to end the
+ * response, for exampe {@link RoutingContext}.
  * If the annotated method does not return {@code void} then the arguments are optional.
  * <p>
  * If both {@link #path()} and {@link #regex()} are set the regular expression is used for matching.