From d87e8a387fe4af9dd2befa291adc7ba80f8c9116 Mon Sep 17 00:00:00 2001
From: Christian Beikov <christian.beikov@gmail.com>
Date: Mon, 2 Aug 2021 09:32:15 +0200
Subject: [PATCH] HHH-14768 Fix recursive type variable rendering

---
 .../jpamodelgen/util/TypeRenderingVisitor.java        |  6 +++++-
 .../CollectionAsBasicTypeTest.java                    |  7 +++++++
 .../test/collectionbasictype/EnumHolder.java          | 11 +++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/EnumHolder.java

diff --git a/tooling/metamodel-generator/src/main/java/org/hibernate/jpamodelgen/util/TypeRenderingVisitor.java b/tooling/metamodel-generator/src/main/java/org/hibernate/jpamodelgen/util/TypeRenderingVisitor.java
index 5652b37991..8654c95d84 100644
--- a/tooling/metamodel-generator/src/main/java/org/hibernate/jpamodelgen/util/TypeRenderingVisitor.java
+++ b/tooling/metamodel-generator/src/main/java/org/hibernate/jpamodelgen/util/TypeRenderingVisitor.java
@@ -6,7 +6,9 @@
  */
 package org.hibernate.jpamodelgen.util;
 
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import javax.lang.model.element.Element;
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.TypeParameterElement;
@@ -30,6 +32,7 @@ import javax.lang.model.util.SimpleTypeVisitor8;
 public final class TypeRenderingVisitor extends SimpleTypeVisitor8<Object, Object> {
 
 	private final StringBuilder sb = new StringBuilder();
+	private final Set<TypeVariable> visitedTypeVariables = new HashSet<>();
 
 	private TypeRenderingVisitor() {
 	}
@@ -129,9 +132,10 @@ public final class TypeRenderingVisitor extends SimpleTypeVisitor8<Object, Objec
 		if ( typeVariableElement instanceof TypeParameterElement ) {
 			final TypeParameterElement typeParameter = (TypeParameterElement) typeVariableElement;
 			sb.append( typeParameter );
-			if ( !"java.lang.Object".equals( t.getUpperBound().toString() ) ) {
+			if ( !"java.lang.Object".equals( t.getUpperBound().toString() ) && visitedTypeVariables.add( t ) ) {
 				sb.append( " extends " );
 				t.getUpperBound().accept( this, null );
+				visitedTypeVariables.remove( t );
 			}
 		}
 		else {
diff --git a/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/CollectionAsBasicTypeTest.java b/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/CollectionAsBasicTypeTest.java
index b00743c4da..5fd388e6ea 100644
--- a/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/CollectionAsBasicTypeTest.java
+++ b/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/CollectionAsBasicTypeTest.java
@@ -93,4 +93,11 @@ public class CollectionAsBasicTypeTest extends CompilationTest {
 	public void testIntersectionType() {
 		assertMetamodelClassGeneratedFor( ConcreteLike.class );
 	}
+
+	@Test
+	@TestForIssue(jiraKey = "HHH-14724")
+	@WithClasses({ EnumHolder.class })
+	public void testRecursiveTypeVariable() {
+		assertMetamodelClassGeneratedFor( EnumHolder.class );
+	}
 }
diff --git a/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/EnumHolder.java b/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/EnumHolder.java
new file mode 100644
index 0000000000..7f8ea324a4
--- /dev/null
+++ b/tooling/metamodel-generator/src/test/java/org/hibernate/jpamodelgen/test/collectionbasictype/EnumHolder.java
@@ -0,0 +1,11 @@
+package org.hibernate.jpamodelgen.test.collectionbasictype;
+
+import javax.persistence.Entity;
+
+@Entity
+public class EnumHolder {
+
+	public <E extends Enum<E>> E getMyEnum() {
+		return null;
+	}
+}