From b29fdc5058d6174f72ddf09cf0dfd2fafd3c657f Mon Sep 17 00:00:00 2001
From: Tobias Gierke <tobias.gierke@code-sourcery.de>
Date: Fri, 13 Oct 2023 18:45:09 +0200
Subject: [PATCH] Make Types#isLambdaType work on JDK >= 21

---
 .../com/thoughtworks/xstream/core/util/Types.java    | 12 +++++++++---
 .../test/com/thoughtworks/acceptance/LambdaTest.java |  6 ++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/xstream/src/java/com/thoughtworks/xstream/core/util/Types.java b/xstream/src/java/com/thoughtworks/xstream/core/util/Types.java
index 5168be7a3..9ea639f37 100644
--- a/xstream/src/java/com/thoughtworks/xstream/core/util/Types.java
+++ b/xstream/src/java/com/thoughtworks/xstream/core/util/Types.java
@@ -16,10 +16,16 @@
  * @since 1.4.8
  */
 public class Types {
-    private static final Pattern lambdaPattern = Pattern.compile(".*\\$\\$Lambda\\$[0-9]+/.*");
+    private static final Pattern lambdaPattern = Pattern.compile(".*\\$\\$Lambda(?:\\$[0-9]+|)/.*");
 
     public static final boolean isLambdaType(final Class<?> type) {
-        return type != null && type.isSynthetic() && lambdaPattern.matcher(type.getSimpleName()).matches();
+        if (type != null && type.isSynthetic()) {
+            String typeName = type.getSimpleName();
+            if (typeName.length() == 0) { // JDK >= 17: JDK-8254979 makes getSimpleName() return "" for lambdas
+              typeName = type.getName();
+            }
+            return lambdaPattern.matcher(typeName).matches();
+        }
+        return false;
     }
-
 }
diff --git a/xstream/src/test/com/thoughtworks/acceptance/LambdaTest.java b/xstream/src/test/com/thoughtworks/acceptance/LambdaTest.java
index e0c6c8024..01d2b8eda 100644
--- a/xstream/src/test/com/thoughtworks/acceptance/LambdaTest.java
+++ b/xstream/src/test/com/thoughtworks/acceptance/LambdaTest.java
@@ -199,8 +199,10 @@ private void assertBothWaysNormalized(final Object original, final String expect
     }
 
     private String normalizeLambda(final String xml) {
-        // unify compiler specific name for implMethodName, Eclipse uses always "lambda$0"
-        return xml.replaceAll(">lambda\\$[^<]+<", ">lambda\\$0<");
+        // unify compiler specific name for implMethodName (Eclipse uses always "lambda$0")
+        // and implMethodKind (varies between at least JDK17 and JDK21 in some cases)
+        return xml.replaceAll( ">lambda\\$[^<]+<", ">lambda\\$0<" )
+            .replaceAll( "<implMethodKind>\\d+</implMethodKind>", "<implMethodKind>5</implMethodKind>" );
     }
 
     public void testTreeSetWithLambda() {