React Vanilla enum renderer removes empty data

Instead of the empty string the React Vanilla enum renderer will now hand over
'undefined' to handleChange and therefore delete the corresponding attribute.

Author: sdirix

packages/vanilla/src/cells/EnumCell.tsx

@@ -43,7 +43,7 @@ export const EnumCell = (props: EnumCellProps & VanillaRendererProps) => {
       disabled={!enabled}
       autoFocus={uischema.options && uischema.options.focus}
       value={data || ''}
-      onChange={ev => handleChange(path, ev.target.value)}
+      onChange={ev => handleChange(path, ev.target.selectedIndex === 0 ? undefined : ev.target.value)}
     >
       {
         [<option value='' key={'empty'} />]

packages/vanilla/test/renderers/EnumCell.test.tsx

@@ -188,6 +188,27 @@ describe('Enum cell', () => {
     expect(onChangeData.data.foo).toBe('b');
   });
 
+  test('empty selection should lead to data deletion', () => {
+    const onChangeData: any = {
+      data: undefined
+    };
+    const core = initCore(fixture.schema, fixture.uischema, fixture.data);
+    wrapper = mount(
+      <JsonFormsStateProvider initState={{ core }}>
+        <TestEmitter
+          onChange={({ data }) => {
+            onChangeData.data = data;
+          }}
+        />
+        <EnumCell schema={fixture.schema} uischema={fixture.uischema} path='foo' />
+      </JsonFormsStateProvider>
+    );
+    expect(onChangeData.data.foo).toBe('a');
+    const select = wrapper.find('select');
+    select.simulate('change', { target: { selectedIndex: 0 } });
+    expect(onChangeData.data.foo).toBe(undefined);
+  });
+
   test('update via action', () => {
     const data = { 'foo': 'b' };
     const core = initCore(fixture.schema, fixture.uischema, data);