feat: expose index in FormDataConsumer

packages/ra-core/src/form/FormDataConsumer.spec.tsx

@@ -140,4 +140,37 @@ describe('FormDataConsumerView', () => {
             });
         });
     });
+
+    it('calls its children with the index when inside an ArrayInput', async () => {
+        let globalIndex;
+
+        render(
+            <AdminContext dataProvider={testDataProvider()}>
+                <ResourceContextProvider value="posts">
+                    <SimpleForm>
+                        <ArrayInput source="authors">
+                            <SimpleFormIterator>
+                                <FormDataConsumer>
+                                    {({ index }) => {
+                                        globalIndex = index;
+                                        return null;
+                                    }}
+                                </FormDataConsumer>
+                            </SimpleFormIterator>
+                        </ArrayInput>
+                    </SimpleForm>
+                </ResourceContextProvider>
+            </AdminContext>
+        );
+
+        expect(globalIndex).toEqual(undefined);
+
+        fireEvent.click(screen.getByLabelText('ra.action.add'));
+
+        expect(globalIndex).toEqual(0);
+
+        fireEvent.click(screen.getByLabelText('ra.action.add'));
+
+        expect(globalIndex).toEqual(1);
+    });
 });

packages/ra-core/src/form/FormDataConsumer.tsx

@@ -77,7 +77,8 @@ export const FormDataConsumerView = <
     // If we have an index, we are in an iterator like component (such as the SimpleFormIterator)
     if (arraySource) {
         const scopedFormData = get(formData, arraySource);
-        result = children({ formData, scopedFormData });
+        const index = Number(arraySource.match(/\d+$/)?.[0]);
+        result = children({ formData, scopedFormData, index });
     } else {
         result = children({ formData });
     }
@@ -98,6 +99,7 @@ export interface FormDataConsumerRenderParams<
 > {
     formData: TFieldValues;
     scopedFormData?: TScopedFieldValues;
+    index?: number;
 }
 
 export type FormDataConsumerRender<