fix rjsf-team#3759

Author: jaejoon-daim

packages/core/src/components/fields/ObjectField.tsx

@@ -13,6 +13,7 @@ import {
   TranslatableString,
   ADDITIONAL_PROPERTY_FLAG,
   PROPERTIES_KEY,
+  DEFAULT_KEY,
   REF_KEY,
   ANY_OF_KEY,
   ONE_OF_KEY,
@@ -137,7 +138,7 @@ class ObjectField<T = any, S extends StrictRJSFSchema = RJSFSchema, F extends Fo
       if (oldValue === value) {
         return;
       }
-      const { formData, onChange, errorSchema } = this.props;
+      const { formData, onChange, errorSchema, schema } = this.props;
 
       value = this.getAvailableKey(value, formData);
       const newFormData: GenericObjectType = {
@@ -152,6 +153,12 @@ class ObjectField<T = any, S extends StrictRJSFSchema = RJSFSchema, F extends Fo
 
       this.setState({ wasPropertyKeyModified: true });
 
+      if (DEFAULT_KEY in schema) {
+        const defaults = schema[DEFAULT_KEY] as GenericObjectType;
+        unset(defaults, oldValue);
+        set(defaults, value, newFormData[oldValue]);
+      }
+
       onChange(
         renamedObj,
         errorSchema &&