fix(Form): avoid merging sparse list patches into allValue

src/useForm.ts

@@ -788,10 +788,10 @@ export class FormStore {
       const changedValues = cloneByNamePathList(this.store, [namePath]);
       const allValues = this.getFieldsValue();
       // Merge changedValues into allValues to ensure allValues contains the latest changes
-      const mergedAllValues = mergeWith([allValues, changedValues], {
-        // When value is array, it means trigger by Form.List which should replace directly
-        prepareArray: current => (fieldEntity?.isList() ? [] : [...(current || [])]),
-      });
+      let mergedAllValues = allValues;
+      if (fieldEntity?.isList()) {
+        mergedAllValues = mergeWith([allValues, changedValues]);
+      }
       onValuesChange(changedValues, mergedAllValues);
     }
 

tests/list.test.tsx

@@ -1139,4 +1139,36 @@ describe('Form.List', () => {
       { list: [{ name: 'John', tags: ['react', 'ts', 'redux'] }] },
     );
   });
+
+  it('should not drop list items when updating list item field', async () => {
+    const onValuesChange = jest.fn();
+
+    const { getAllByRole } = render(
+      <Form onValuesChange={onValuesChange}>
+        <Form.List
+          name="list"
+          initialValue={[{ name: 'A' }, { name: 'B' }, { name: 'C' }, { name: 'D' }]}
+        >
+          {fields =>
+            fields.map(field => (
+              <Field key={field.key} name={[field.name, 'name']}>
+                <input />
+              </Field>
+            ))
+          }
+        </Form.List>
+      </Form>,
+    );
+
+    // Change second item (index = 1)
+    fireEvent.change(getAllByRole('textbox')[1], {
+      target: { value: 'BB' },
+    });
+
+    const [, allValues] = onValuesChange.mock.calls.pop();
+
+    expect(allValues).toEqual({
+      list: [{ name: 'A' }, { name: 'BB' }, { name: 'C' }, { name: 'D' }],
+    });
+  });
 });