Fix <AutocompleteArrayInput> silently ignoring emptyText and emptyValue

docs/AutocompleteArrayInput.md

@@ -64,7 +64,6 @@ The form value for the source must be an array of the selected values, e.g.
 | `createLabel`              | Optional | `string` | `ReactNode`                     | -                        | The label used as hint to let users know they can create a new choice. Displayed when the filter is empty.                                       |
 | `createItemLabel`          | Optional | `string` | `(filter: string) => ReactNode` | `ra.action .create_item` | The label for the menu item allowing users to create a new choice. Used when the filter is not empty.                                                    |
 | `debounce`                 | Optional | `number`                                        | `250`                    | The delay to wait before calling the setFilter function injected when used in a ReferenceArray Input.                                                         |
-| `emptyValue`               | Optional | `any`                                           | `''`                     | The value to use for the empty element                                                                                                                  |
 | `filterToQuery`            | Optional | `string` => `Object`                            | `q => ({ q })`           | How to transform the searchText into a parameter for the data provider                                                                                  |
 | `inputText`                | Optional | `Function`                                      | `-`                      | Required if `optionText` is a custom Component, this function must return the text displayed for the current selection.                                 |
 | `matchSuggestion`          | Optional | `Function`                                      | `-`                      | Required if `optionText` is a React element. Function returning a boolean indicating whether a choice matches the filter. `(filter, choice) => boolean` |
@@ -298,18 +297,6 @@ This delay can be customized by setting the `debounce` prop.
 </ReferenceArrayInput>
 ```
 
-## `emptyValue`
-
-If the input isn't required (using `validate={required()}`), users can select an empty choice. The default value for that empty choice is the empty string (`''`), or `null` if the input is inside a [`<ReferenceArrayInput>`](./ReferenceArrayInput.md).
-
-You can override this value with the `emptyValue` prop.
-
-```jsx
-<AutocompleteArrayInput source="roles" choices={choices} emptyValue={0} />
-```
-
-**Tip**: While you can set `emptyValue` to a non-string value (e.g. `0`), you cannot use `null` or `undefined`, as it would turn the `<AutocompleteArrayInput>` into an [uncontrolled component](https://react.dev/learn/sharing-state-between-components#controlled-and-uncontrolled-components). If you need the empty choice to be stored as `null` or `undefined`, use [the `parse` prop](./Inputs.md#parse) to convert the default empty value (`''`) to `null` or `undefined`, or use [the `sanitizeEmptyValues` prop](./SimpleForm.md#sanitizeemptyvalues) on the Form component. 
-
 ## `filterToQuery`
 
 When used inside a [`<ReferenceArrayInput>`](./ReferenceArrayInput.md), whenever users type a string in the autocomplete input, `<AutocompleteArrayInput>` calls `dataProvider.getList()` using the string as filter, to return a filtered list of possible options from the reference resource. This filter is built using the `filterToQuery` prop.

packages/ra-ui-materialui/src/input/AutocompleteInput.spec.tsx

@@ -260,6 +260,39 @@ describe('<AutocompleteInput />', () => {
             expect(screen.queryByText('Default')).toBeNull();
             await screen.findByText('No options');
         });
+
+        it('should not display the emptyText when multiple is true', async () => {
+            const mock = jest
+                .spyOn(console, 'warn')
+                .mockImplementation(() => {});
+            render(
+                <AdminContext dataProvider={testDataProvider()}>
+                    <ResourceContextProvider value="posts">
+                        <SimpleForm onSubmit={jest.fn()}>
+                            <AutocompleteInput
+                                emptyText="Default"
+                                {...defaultProps}
+                                choices={[{ id: 2, name: 'foo' }]}
+                                multiple
+                            />
+                        </SimpleForm>
+                    </ResourceContextProvider>
+                </AdminContext>
+            );
+            fireEvent.click(
+                await screen.findByLabelText('resources.users.fields.role')
+            );
+            await waitFor(() => {
+                expect(screen.queryAllByRole('option').length).toEqual(1);
+            });
+            expect(screen.queryByText('Default')).toBeNull();
+            expect(mock).toHaveBeenCalledWith(
+                expect.stringContaining(
+                    'emptyText and emptyValue are not supported when multiple is true'
+                )
+            );
+            mock.mockRestore();
+        });
     });
 
     describe('optionValue', () => {

packages/ra-ui-materialui/src/input/AutocompleteInput.tsx

@@ -314,6 +314,15 @@ If you provided a React element for the optionText prop, you must also provide t
         }
     }, [optionText, inputText, matchSuggestion, emptyText, isFromReference]);
 
+    useEffect(() => {
+        warning(
+            multiple &&
+                (props.emptyText !== undefined ||
+                    props.emptyValue !== undefined),
+            `emptyText and emptyValue are not supported when multiple is true (e.g. in <AutocompleteArrayInput>): the empty value of a multi-valued input is an empty array, so it needs no empty choice. These props are ignored.`
+        );
+    }, [multiple, props.emptyText, props.emptyValue]);
+
     useEffect(() => {
         warning(
             /* eslint-disable eqeqeq */