Fix #3373

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -6,7 +6,8 @@ Project: jackson-databind
 
 2.14.0 (not yet released)
 
-No changes since 2.13
+#3373: Change `TypeSerializerBase` to skip `generator.writeTypePrefix()`
+  for `null` typeId
 
 2.13.2 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/jsontype/impl/TypeSerializerBase.java

@@ -43,13 +43,23 @@ public WritableTypeId writeTypePrefix(JsonGenerator g,
             WritableTypeId idMetadata) throws IOException
     {
         _generateTypeId(idMetadata);
+        // 16-Jan-2022, tatu: As per [databind#3373], skip for null typeId.
+        //    And return "null" so that matching "writeTypeSuffix" call should
+        //    be avoided as well.
+        if (idMetadata.id == null) {
+            return null;
+        }
         return g.writeTypePrefix(idMetadata);
     }
 
     @Override
     public WritableTypeId writeTypeSuffix(JsonGenerator g,
             WritableTypeId idMetadata) throws IOException
     {
+        // 16-Jan-2022, tatu: As per [databind#3373], skip for null:
+        if (idMetadata == null) {
+            return null;
+        }
         return g.writeTypeSuffix(idMetadata);
     }