Test In-comparable Map with enabled Ser..Feature.ORDER_MAP_ENTRIES_BY_KEYS failure wrt #4773

src/test/java/com/fasterxml/jackson/databind/tofix/OrderMapEntriesByKeysSerializationFeature4773Test.java

@@ -0,0 +1,78 @@
+package com.fasterxml.jackson.databind.tofix;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Currency;
+import java.util.HashMap;
+import java.util.Map;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+import com.fasterxml.jackson.databind.testutil.failure.JacksonTestFailureExpected;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+// [databind#4773] Test to verify `SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS` behavior
+//     when serializing `Map` instances with un-comparable keys.
+public class OrderMapEntriesByKeysSerializationFeature4773Test
+        extends DatabindTestUtil
+{
+
+    public static class IncomparableContainer4773 {
+        public Map<Currency, String> exampleMap = new HashMap<>();
+    }
+
+    public static class ObjectContainer4773 {
+        public Map<Object, String> exampleMap = new HashMap<>();
+    }
+
+    private final ObjectMapper objectMapper = jsonMapperBuilder()
+            .configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true)
+            .build();
+
+    @JacksonTestFailureExpected
+    @Test
+    void testSerializationWithIncomparableKeys()
+            throws Exception
+    {
+        // Given
+        IncomparableContainer4773 entity = new IncomparableContainer4773();
+        entity.exampleMap.put(Currency.getInstance("GBP"), "GBP_TEXT");
+        entity.exampleMap.put(Currency.getInstance("AUD"), "AUD_TEXT");
+
+        // When : Throws exception
+        // com.fasterxml.jackson.databind.JsonMappingException: class java.util.Currency cannot be cast to class java.lang.Comparable
+        String jsonResult = objectMapper.writeValueAsString(entity);
+
+        // Then : Order should not matter, just plain old serialize
+        assertTrue(jsonResult.contains("GBP"));
+        assertTrue(jsonResult.contains("AUD"));
+    }
+
+    @Test
+    void testSerializationWithGenericObjectKeys()
+            throws Exception
+    {
+        // Given
+        ObjectContainer4773 entity = new ObjectContainer4773();
+        entity.exampleMap.put(5, "N_TEXT");
+        entity.exampleMap.put(1, "GBP_TEXT");
+        entity.exampleMap.put(3, "T_TEXT");
+        entity.exampleMap.put(4, "AUD_TEXT");
+        entity.exampleMap.put(2, "KRW_TEXT");
+
+        // When
+        String jsonResult = objectMapper.writeValueAsString(entity);
+
+        // Then
+        assertEquals(a2q("{'exampleMap':{" +
+                "'1':'GBP_TEXT'," +
+                "'2':'KRW_TEXT'," +
+                "'3':'T_TEXT'," +
+                "'4':'AUD_TEXT'," +
+                "'5':'N_TEXT'}}"), jsonResult);
+    }
+
+}