From d9dc0ffec3527b2cd8b75fdd7274d19d4cd58d3d Mon Sep 17 00:00:00 2001
From: Georgios Andrianakis <geoand@gmail.com>
Date: Thu, 26 Aug 2021 13:48:12 +0300
Subject: [PATCH] Add an actionable message when attribute of multipart is a
 file and not accessed as such

Closes: #19677
---
 .../MultipartPopulatorGenerator.java           |  4 ++--
 .../runtime/multipart/MultipartSupport.java    | 18 +++++++++++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/main/java/io/quarkus/resteasy/reactive/server/deployment/MultipartPopulatorGenerator.java b/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/main/java/io/quarkus/resteasy/reactive/server/deployment/MultipartPopulatorGenerator.java
index f05f9dd80b16b..e02091633f902 100644
--- a/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/main/java/io/quarkus/resteasy/reactive/server/deployment/MultipartPopulatorGenerator.java
+++ b/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/main/java/io/quarkus/resteasy/reactive/server/deployment/MultipartPopulatorGenerator.java
@@ -394,11 +394,11 @@ static String generate(ClassInfo multipartClassInfo, ClassOutput classOutput, In
                                             String.class,
                                             Class.class,
                                             java.lang.reflect.Type.class, MediaType.class,
-                                            ResteasyReactiveRequestContext.class),
+                                            ResteasyReactiveRequestContext.class, String.class),
                                     formStrValueHandle, populate.readStaticField(typeField),
                                     populate.readStaticField(genericTypeField),
                                     populate.readStaticField(mediaTypeField),
-                                    rrCtxHandle));
+                                    rrCtxHandle, formAttrNameHandle));
                         }
                     }
 
diff --git a/extensions/resteasy-reactive/quarkus-resteasy-reactive/runtime/src/main/java/io/quarkus/resteasy/reactive/server/runtime/multipart/MultipartSupport.java b/extensions/resteasy-reactive/quarkus-resteasy-reactive/runtime/src/main/java/io/quarkus/resteasy/reactive/server/runtime/multipart/MultipartSupport.java
index 979fb51e18c84..1ee6f0fe2278b 100644
--- a/extensions/resteasy-reactive/quarkus-resteasy-reactive/runtime/src/main/java/io/quarkus/resteasy/reactive/server/runtime/multipart/MultipartSupport.java
+++ b/extensions/resteasy-reactive/quarkus-resteasy-reactive/runtime/src/main/java/io/quarkus/resteasy/reactive/server/runtime/multipart/MultipartSupport.java
@@ -20,6 +20,7 @@
 import javax.ws.rs.ext.MessageBodyReader;
 
 import org.jboss.logging.Logger;
+import org.jboss.resteasy.reactive.multipart.FileUpload;
 import org.jboss.resteasy.reactive.server.core.ResteasyReactiveRequestContext;
 import org.jboss.resteasy.reactive.server.core.ServerSerialisers;
 import org.jboss.resteasy.reactive.server.core.multipart.DefaultFileUpload;
@@ -31,6 +32,7 @@
 /**
  * This class isn't used directly, it is however used by generated code meant to deal with multipart forms.
  */
+@SuppressWarnings("unused")
 public final class MultipartSupport {
 
     private static final Logger log = Logger.getLogger(RequestDeserializeHandler.class);
@@ -42,8 +44,22 @@ private MultipartSupport() {
 
     @SuppressWarnings({ "unchecked", "rawtypes" })
     public static Object convertFormAttribute(String value, Class type, Type genericType, MediaType mediaType,
-            ResteasyReactiveRequestContext context) {
+            ResteasyReactiveRequestContext context, String attributeName) {
         if (value == null) {
+            FormData formData = context.getFormData();
+            if (formData != null) {
+                Collection<FormValue> fileUploadsForName = formData.get(attributeName);
+                if (fileUploadsForName != null) {
+                    for (FormData.FormValue fileUpload : fileUploadsForName) {
+                        if (fileUpload.isFileItem()) {
+                            log.debug("Attribute '" + attributeName
+                                    + "' of the multipart request is a file and therefore its value is not set. To obtain the contents of the file, use type '"
+                                    + FileUpload.class + "' as the field type.");
+                            break;
+                        }
+                    }
+                }
+            }
             return null;
         }