Add test for FasterXML#2821

Author: lhotari

src/test/java/com/fasterxml/jackson/failing/TypeFactoryConstructTypeRegression2821Test.java

@@ -0,0 +1,83 @@
+package com.fasterxml.jackson.failing;
+
+import com.fasterxml.jackson.annotation.*;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.util.*;
+
+// Tests for [#2821]
+public class TypeFactoryConstructTypeRegression2821Test extends BaseMapTest {
+    static final class Wrapper {
+        // if Entity<?> -> Entity , the test passes
+        private final List<Entity<?>> entities;
+
+        @JsonCreator
+        public Wrapper(List<Entity<?>> entities) {
+            this.entities = entities;
+        }
+
+        public List<Entity<?>> getEntities() {
+            return this.entities;
+        }
+    }
+
+    public static class Entity<T> {
+        @JsonIgnore
+        private final Attributes attributes;
+
+        private final T data;
+
+        public Entity(Attributes attributes, T data) {
+            this.attributes = attributes;
+            this.data = data;
+        }
+
+        // if @JsonUnwrapped is removed, the test passes
+        @JsonUnwrapped
+        public Attributes getAttributes() {
+            return attributes;
+        }
+
+        public T getData() {
+            return data;
+        }
+
+        @JsonCreator
+        public static <T> Entity<T> create(Attributes attributes, T data) {
+            return new Entity<>(attributes, data);
+        }
+    }
+
+    public static class Attributes {
+        private final String id;
+
+        public Attributes(String id) {
+            this.id = id;
+        }
+
+        public String getId() {
+            return id;
+        }
+
+        @JsonCreator
+        public static Attributes create(String id) {
+            return new Attributes(id);
+        }
+
+        // if this method is removed, the test passes
+        public static Attributes dummyMethod(Map attributes) {
+            return null;
+        }
+    }
+
+    // this test passes with Jackson 2.11.1, but fails with Jackson 2.11.2
+    public void testReproduceSerializerBug() throws JsonProcessingException {
+        ObjectMapper objectMapper = new ObjectMapper().findAndRegisterModules();
+        Entity<String> entity = new Entity<>(new Attributes("id"), "hello");
+        Wrapper val = new Wrapper(Collections.<Entity<?>>singletonList(entity));
+        // fails with com.fasterxml.jackson.databind.JsonMappingException: Strange Map type java.util.Map: cannot determine type parameters (through reference chain: com.github.lhotari.jacksonbug.JacksonBugIsolatedTest$Wrapper["entities"]->java.util.Collections$SingletonList[0]->com.github.lhotari.jacksonbug.JacksonBugIsolatedTest$Entity["attributes"])
+        System.out.println(objectMapper.writeValueAsString(val));
+    }
+}