Add reproduction (unit test) for #4118 (#4128)

* add test

* clean up

Author: JooHyukKim

src/main/java/com/fasterxml/jackson/databind/type/TypeBindings.java

@@ -217,6 +217,8 @@ public TypeBindings withUnboundVariable(String name)
      * Create a new instance with the same bindings as this object, except with
      * the given variable removed. This is used to create generic types that are
      * "partially raw", i.e. only have some variables bound.
+     *
+     * @since 2.16
      */
     public TypeBindings withoutVariable(String name)
     {

src/main/java/com/fasterxml/jackson/databind/type/TypeFactory.java

@@ -1706,8 +1706,8 @@ protected JavaType _fromParamType(ClassStack context, ParameterizedType ptype,
             }
             newBindings = TypeBindings.create(rawType, pt);
 
-            // jackson-databind#4118: Unbind any wildcards with a less specific upper bound than
-            // declared on the type variable
+            // [databind#4118] Unbind any wildcards with a less specific upper bound than
+            // declared on the type variable (since 2.16)
             for (int i = 0; i < paramCount; ++i) {
                 if (args[i] instanceof WildcardType && !pt[i].hasGenericTypes()) {
                     TypeVariable<? extends Class<?>> typeVariable = rawType.getTypeParameters()[i];

src/test/java/com/fasterxml/jackson/databind/type/RecursiveWildcardTest.java

@@ -1,5 +1,6 @@
 package com.fasterxml.jackson.databind.type;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -11,19 +12,7 @@
 
 public class RecursiveWildcardTest extends BaseMapTest
 {
-    public void test() throws Exception
-    {
-        ObjectMapper mapper = newJsonMapper();
-
-        Tree<?> tree = mapper.readValue("[[[]]]", new TypeReference<Tree<?>>() {
-        });
-
-        assertEquals(1, tree.children.size());
-        assertEquals(1, tree.children.get(0).children.size());
-        assertEquals(0, tree.children.get(0).children.get(0).children.size());
-    }
-
-    public static class Tree<T extends Tree<?>> {
+    static class Tree<T extends Tree<?>> {
 
         final List<T> children;
 
@@ -35,6 +24,63 @@ public Tree(List<T> children) {
             }
             this.children = children;
         }
+    }
+
+    static class TestAttribute4118<T extends TestAttribute4118<?>> {
+
+        public List<T> attributes;
+
+        public TestAttribute4118() { }
+
+        public TestAttribute4118(List<T> attributes) {
+            this.attributes = attributes;
+        }
+    }
+
+    static class TestObject4118 {
+
+        public List<TestAttribute4118<?>> attributes = new ArrayList<>();
+
+        public TestObject4118() { }
+
+        public TestObject4118(List<TestAttribute4118<?>> attributes) {
+            this.attributes = attributes;
+        }
+    }
+
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    public void testRecursiveWildcard() throws Exception
+    {
+        Tree<?> tree = MAPPER.readValue("[[[]]]", new TypeReference<Tree<?>>() {
+        });
+
+        assertEquals(1, tree.children.size());
+        assertEquals(1, tree.children.get(0).children.size());
+        assertEquals(0, tree.children.get(0).children.get(0).children.size());
+    }
+
+    // for [databind#4118]
+    public void testDeserWildcard4118() throws Exception
+    {
+        // Given
+        TestAttribute4118 a = new TestAttribute4118(null);
+        TestAttribute4118 b = new TestAttribute4118(_listOf(a));
+        TestAttribute4118 c = new TestAttribute4118(_listOf(b));
+        TestObject4118 test = new TestObject4118(_listOf(c));
+
+        String serialized = MAPPER.writeValueAsString(test);
+
+        // When
+        TestObject4118 deserialized = MAPPER.readValue(serialized, TestObject4118.class);
+
+        // Then
+        assertType(deserialized.attributes.get(0).attributes.get(0), TestAttribute4118.class);
+    }
 
+    private <T> List<T> _listOf(T elem) {
+        ArrayList<T> list = new ArrayList<>();
+        list.add(elem);
+        return list;
     }
 }