From d6cbd4069259b981691f8404ceb55f47319d5ce1 Mon Sep 17 00:00:00 2001
From: Ryan Ernst <ryan@iernst.net>
Date: Mon, 31 Mar 2025 08:19:11 -0700
Subject: [PATCH] Return null from transformer when not transforming

The transform API for instrumentation should return null when no
transformation occurs. This commit fixes our entitlement transformer to
return null instead of the original buffer.

closesn #125920
---
 .../elasticsearch/entitlement/instrumentation/Transformer.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libs/entitlement/src/main/java/org/elasticsearch/entitlement/instrumentation/Transformer.java b/libs/entitlement/src/main/java/org/elasticsearch/entitlement/instrumentation/Transformer.java
index 1977f767014d0..6d4d4edaae162 100644
--- a/libs/entitlement/src/main/java/org/elasticsearch/entitlement/instrumentation/Transformer.java
+++ b/libs/entitlement/src/main/java/org/elasticsearch/entitlement/instrumentation/Transformer.java
@@ -46,7 +46,7 @@ public byte[] transform(
             return instrumenter.instrumentClass(className, classfileBuffer, verifyClasses);
         } else {
             // System.out.println("Not transforming " + className);
-            return classfileBuffer;
+            return null;
         }
     }