From 1c5b7575385ad48eeaa6de221899d4eeca04cf4a Mon Sep 17 00:00:00 2001
From: Georgios Andrianakis <geoand@gmail.com>
Date: Tue, 25 May 2021 09:53:30 +0300
Subject: [PATCH] Fail at build time if @Inject is used in JAX-RS Application
 class

Relates to: #17441
---
 .../processor/scanning/ResteasyReactiveScanner.java | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/scanning/ResteasyReactiveScanner.java b/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/scanning/ResteasyReactiveScanner.java
index 55b2e9c5a6d35..f75fe16974211 100644
--- a/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/scanning/ResteasyReactiveScanner.java
+++ b/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/scanning/ResteasyReactiveScanner.java
@@ -66,7 +66,10 @@ public static ApplicationScanningResult scanForApplicationClass(IndexView index,
                 throw new RuntimeException("More than one Application class: " + applications);
             }
             selectedAppClass = applicationClassInfo;
-            // FIXME: yell if there's more than one
+            if (appClassHasInject(selectedAppClass)) {
+                throw new RuntimeException("'@Inject' cannot be used with a '" + ResteasyReactiveDotNames.APPLICATION
+                        + "' class. Offending class is: '" + selectedAppClass.name() + "'");
+            }
             String applicationClass = applicationClassInfo.name().toString();
             try {
                 Class<?> appClass = Thread.currentThread().getContextClassLoader().loadClass(applicationClass);
@@ -104,6 +107,14 @@ public static ApplicationScanningResult scanForApplicationClass(IndexView index,
                 selectedAppClass, blocking);
     }
 
+    private static boolean appClassHasInject(ClassInfo appClass) {
+        if (appClass.annotations() == null) {
+            return false;
+        }
+        List<AnnotationInstance> injectInstances = appClass.annotations().get(ResteasyReactiveDotNames.CDI_INJECT);
+        return (injectInstances != null) && !injectInstances.isEmpty();
+    }
+
     public static ResourceScanningResult scanResources(
             IndexView index) {
         Collection<AnnotationInstance> paths = index.getAnnotations(ResteasyReactiveDotNames.PATH);