Add failing test against #4680

src/test/java/com/fasterxml/jackson/failing/CustomObjectKeyDeserializer4680Test.java

@@ -0,0 +1,70 @@
+package com.fasterxml.jackson.failing;
+
+import java.util.Map;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.KeyDeserializer;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+// [databind#4680] Custom key deserialiser registered for `Object.class` is ignored on nested JSON
+public class CustomObjectKeyDeserializer4680Test
+{
+
+    @Test
+    void testCustomKeyDeserializer()
+            throws Exception
+    {
+        // GIVEN
+        String json =
+                "{\n" +
+                        "     \"name*\": \"Erik\",\n" +
+                        "     \"address*\": {\n" +
+                        "         \"city*\": {\n" +
+                        "             \"id*\": 1,\n" +
+                        "             \"name*\": \"Berlin\"\n" +
+                        "         },\n" +
+                        "         \"street*\": \"Elvirastr\"\n" +
+                        "     }\n" +
+                        " }";
+
+        SimpleModule keySanitizationModule = new SimpleModule("key-sanitization");
+        keySanitizationModule.addKeyDeserializer(String.class, new KeyDeserializer() {
+            @Override
+            public String deserializeKey(String key, DeserializationContext ctxt) {
+                return key.replace("*", "_");
+            }
+        });
+
+        keySanitizationModule.addKeyDeserializer(Object.class, new KeyDeserializer() {
+            @Override
+            public Object deserializeKey(String key, DeserializationContext ctxt) {
+                return key.replace("*", "_");
+            }
+        });
+
+        ObjectMapper mapper = JsonMapper.builder().addModule(keySanitizationModule).build();
+
+        // WHEN
+        Map<String, Object> result = mapper.readValue(json, new TypeReference<Map<String, Object>>() {
+        });
+
+        // THEN
+        // depth 1 works as expected
+        Assertions.assertEquals("Erik", result.get("name_"));
+
+        // before fix, depth 2 does NOT work as expected
+        Map<String, Object> addressMap = (Map<String, Object>) result.get("address_");
+        // before fix, null?? Fails here
+        Assertions.assertEquals("Elvirastr", addressMap.get("street_"));
+        Map<String, Object> cityMap = (Map<String, Object>) addressMap.get("city_");
+        Assertions.assertEquals(1, cityMap.get("id_"));
+        Assertions.assertEquals("Berlin", cityMap.get("name_"));
+    }
+
+}