Sanitize the behavior of provided ExceptionMapper classes in dev-mode

User provided ExceptionMapper classes now takes precedence
over the Quarkus provided NotFoundExceptionMapper.

This is done in a way that does not change anything but this
specific behavior, everything else concerning exception handling
continues to work as before.
Note also that this does not change the spec compliance in
any way

Fixes: quarkusio#7883

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

@@ -0,0 +1,64 @@
+package io.quarkus.resteasy.reactive.server.test.devmode;
+
+import static org.hamcrest.CoreMatchers.containsString;
+
+import java.util.function.Supplier;
+
+import jakarta.ws.rs.Consumes;
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.Produces;
+import jakarta.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.QuarkusDevModeTest;
+import io.restassured.RestAssured;
+
+public class QuarkusDefaultExceptionHandlingTest {
+
+    @RegisterExtension
+    static QuarkusDevModeTest TEST = new QuarkusDevModeTest()
+            .setArchiveProducer(new Supplier<>() {
+                @Override
+                public JavaArchive get() {
+                    return ShrinkWrap.create(JavaArchive.class)
+                            .addClasses(Resource.class);
+                }
+
+            });
+
+    @Test
+    public void testDefaultErrorHandler() {
+        RestAssured.given().accept("text/html")
+                .get("/test/exception")
+                .then()
+                .statusCode(500)
+                .body(containsString("Internal Server Error"), containsString("dummy exception"));
+    }
+
+    @Test
+    public void testNotFoundErrorHandler() {
+        RestAssured.given().accept("text/html")
+                .get("/test/exception2")
+                .then()
+                .statusCode(404)
+                .body(containsString("404 - Resource Not Found"));
+    }
+
+    @Path("test")
+    @Produces(MediaType.TEXT_PLAIN)
+    @Consumes(MediaType.TEXT_PLAIN)
+    public static class Resource {
+
+        @Path("exception")
+        @GET
+        @Produces("text/html")
+        public String exception() {
+            throw new RuntimeException("dummy exception");
+        }
+    }
+}

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

@@ -0,0 +1,72 @@
+package io.quarkus.resteasy.reactive.server.test.devmode;
+
+import java.util.function.Supplier;
+
+import jakarta.ws.rs.Consumes;
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.Produces;
+import jakarta.ws.rs.core.MediaType;
+import jakarta.ws.rs.core.Response;
+import jakarta.ws.rs.ext.ExceptionMapper;
+import jakarta.ws.rs.ext.Provider;
+
+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.QuarkusDevModeTest;
+import io.restassured.RestAssured;
+
+public class UserProvidedExceptionHandlingTest {
+
+    @RegisterExtension
+    static QuarkusDevModeTest TEST = new QuarkusDevModeTest()
+            .setArchiveProducer(new Supplier<>() {
+                @Override
+                public JavaArchive get() {
+                    return ShrinkWrap.create(JavaArchive.class)
+                            .addClasses(Resource.class, CustomExceptionMapper.class);
+                }
+
+            });
+
+    @Test
+    public void testDefaultErrorHandler() {
+        RestAssured.given().accept("text/html")
+                .get("/test/exception")
+                .then()
+                .statusCode(999);
+    }
+
+    @Test
+    public void testNotFoundErrorHandler() {
+        RestAssured.given().accept("text/html")
+                .get("/test/exception2")
+                .then()
+                .statusCode(999);
+    }
+
+    @Path("test")
+    @Produces(MediaType.TEXT_PLAIN)
+    @Consumes(MediaType.TEXT_PLAIN)
+    public static class Resource {
+
+        @Path("exception")
+        @GET
+        @Produces("text/html")
+        public String exception() {
+            throw new RuntimeException("dummy exception");
+        }
+    }
+
+    @Provider
+    public static class CustomExceptionMapper implements ExceptionMapper<Exception> {
+        @Override
+        public Response toResponse(Exception exception) {
+            return Response.status(999).build();
+        }
+    }
+
+}

extensions/resteasy-reactive/quarkus-resteasy-reactive/runtime/src/main/java/io/quarkus/resteasy/reactive/server/runtime/NotFoundExceptionMapper.java

@@ -34,6 +34,7 @@
 import org.jboss.logging.Logger;
 import org.jboss.resteasy.reactive.common.util.ServerMediaType;
 import org.jboss.resteasy.reactive.server.ServerExceptionMapper;
+import org.jboss.resteasy.reactive.server.core.RuntimeExceptionMapper;
 import org.jboss.resteasy.reactive.server.core.request.ServerDrivenNegotiation;
 import org.jboss.resteasy.reactive.server.handlers.RestInitialHandler;
 import org.jboss.resteasy.reactive.server.mapping.RequestMapper;
@@ -81,8 +82,12 @@ public MethodDescription(String method, String fullPath, String produces, String
         }
     }
 
-    @ServerExceptionMapper(value = NotFoundException.class, priority = Priorities.USER + 1)
-    public Response toResponse(HttpHeaders headers) {
+    // we don't use NotFoundExceptionMapper here because that would result in users not being able to provide their own catch-all exception mapper in dev-mode, see https://github.com/quarkusio/quarkus/issues/7883
+    @ServerExceptionMapper(priority = Priorities.USER + 1)
+    public Response toResponse(Throwable t, HttpHeaders headers) {
+        if (!(t instanceof NotFoundException)) {
+            return RuntimeExceptionMapper.IGNORE_RESPONSE;
+        }
         if ((classMappers == null) || classMappers.isEmpty()) {
             return respond(headers);
         }

independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/RuntimeExceptionMapper.java

@@ -20,6 +20,7 @@
 import org.jboss.logging.Logger;
 import org.jboss.resteasy.reactive.ResteasyReactiveClientProblem;
 import org.jboss.resteasy.reactive.common.model.ResourceExceptionMapper;
+import org.jboss.resteasy.reactive.server.jaxrs.ResponseBuilderImpl;
 import org.jboss.resteasy.reactive.server.mapping.RuntimeResource;
 import org.jboss.resteasy.reactive.server.spi.ResteasyReactiveAsyncExceptionMapper;
 import org.jboss.resteasy.reactive.server.spi.ResteasyReactiveExceptionMapper;
@@ -42,6 +43,9 @@ public class RuntimeExceptionMapper {
     private final List<Predicate<Throwable>> nonBlockingProblemPredicate;
     private final Set<Class<? extends Throwable>> unwrappedExceptions;
 
+    public static final Response IGNORE_RESPONSE = new ResponseBuilderImpl().status(666).header(
+            "RR_EX_IGN", "true").build();
+
     public RuntimeExceptionMapper(ExceptionMapping mapping, ClassLoader classLoader) {
         try {
             mappers = new HashMap<>();
@@ -94,9 +98,15 @@ public void mapException(Throwable throwable, ResteasyReactiveRequestContext con
             } else {
                 response = exceptionMapper.toResponse(mappedException);
             }
-            context.setResult(response);
-            logBlockingErrorIfRequired(mappedException, context);
-            logNonBlockingErrorIfRequired(mappedException, context);
+            // this special case is used in order to ignore the mapping of built-in mappers and let the exception handling proceed to higher levels
+            if ((IGNORE_RESPONSE == response)) {
+                context.handleUnmappedException(throwable);
+            } else {
+                context.setResult(response);
+                logBlockingErrorIfRequired(mappedException, context);
+                logNonBlockingErrorIfRequired(mappedException, context);
+
+            }
             return;
         }
         if (isWebApplicationException) {