From 2c2194ac1f410c6fbab96f088c7136e7f7cda4c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Merlin=20B=C3=B6gershausen?=
 <merlin.boegershausen@rwth-aachen.de>
Date: Thu, 28 May 2026 18:24:09 +0200
Subject: [PATCH] Skip `RenameUnderscoreIdentifier` on Kotlin and Groovy
 sources

Mirror the precondition gate already used by the sibling
`ReplaceUnusedVariablesWithUnderscore` so the recipe no longer rewrites
legal `_` placeholders in Kotlin lambdas to `__`, which is reserved in
Kotlin 2.0+.
---
 .../lang/RenameUnderscoreIdentifier.java      |  8 +++++++-
 .../lang/RenameUnderscoreIdentifierTest.java  | 20 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifier.java b/src/main/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifier.java
index 6b0b86a602..be45a4b38e 100644
--- a/src/main/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifier.java
+++ b/src/main/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifier.java
@@ -26,6 +26,8 @@
 import org.openrewrite.java.search.UsesJavaVersion;
 import org.openrewrite.java.tree.J;
 import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.staticanalysis.groovy.GroovyFileChecker;
+import org.openrewrite.staticanalysis.kotlin.KotlinFileChecker;
 
 @EqualsAndHashCode(callSuper = false)
 @Value
@@ -40,7 +42,11 @@ public class RenameUnderscoreIdentifier extends Recipe {
     @Override
     public TreeVisitor<?, ExecutionContext> getVisitor() {
         return Preconditions.check(
-                new UsesJavaVersion<>(1, 8),
+                Preconditions.and(
+                        new UsesJavaVersion<>(1, 8),
+                        Preconditions.not(new KotlinFileChecker<>()),
+                        Preconditions.not(new GroovyFileChecker<>())
+                ),
                 new RenameIdentifierVisitor("_", "__")
         );
     }
diff --git a/src/test/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifierTest.java b/src/test/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifierTest.java
index 44e15b4566..d29ad4f73b 100644
--- a/src/test/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifierTest.java
+++ b/src/test/java/org/openrewrite/java/migrate/lang/RenameUnderscoreIdentifierTest.java
@@ -25,6 +25,7 @@
 
 import static org.openrewrite.java.Assertions.java;
 import static org.openrewrite.java.Assertions.javaVersion;
+import static org.openrewrite.kotlin.Assertions.kotlin;
 
 class RenameUnderscoreIdentifierTest implements RewriteTest {
 
@@ -273,6 +274,25 @@ void test() {
         );
     }
 
+    @Test
+    void kotlinFileNotChanged() {
+        rewriteRun(
+          spec -> spec.recipe(new RenameUnderscoreIdentifier())
+            .allSources(s -> s.markers(javaVersion(8))),
+          //language=kotlin
+          kotlin(
+            """
+              class Test {
+                  fun test() {
+                      val pairs = listOf(1 to "a", 2 to "b")
+                      pairs.forEach { _, _ -> println("ignored") }
+                  }
+              }
+              """
+          )
+        );
+    }
+
     @Test
     void forEachLoopVariable() {
         rewriteRun(