fix(@react-aria/datepicker): don't steal focus into a date segment from selectionchange (Firefox)

packages/react-aria-components/test/DateField.test.js

@@ -562,4 +562,32 @@ describe('DateField', () => {
     expect(segements[1]).toHaveTextContent('dd');
     expect(segements[2]).toHaveTextContent('yyyy');
   });
+
+  // Regression test for #10259: in Firefox a stale selection anchor can remain inside a segment
+  // after focus moves away, and the selectionchange handler would collapse onto it, stealing focus.
+  it('does not collapse the selection onto a segment while another element is focused', () => {
+    let {getByRole} = render(
+      <>
+        <button>sibling</button>
+        <DateField defaultValue={new CalendarDate(2020, 2, 3)}>
+          <Label>Date</Label>
+          <DateInput>{segment => <DateSegment segment={segment} />}</DateInput>
+        </DateField>
+      </>
+    );
+
+    let button = getByRole('button');
+    let segment = within(getByRole('group')).getAllByRole('spinbutton').at(-1);
+    act(() => button.focus());
+    expect(document.activeElement).toBe(button);
+
+    let collapse = jest.fn();
+    jest.spyOn(window, 'getSelection').mockReturnValue({anchorNode: segment.firstChild, collapse});
+    act(() => {
+      document.dispatchEvent(new Event('selectionchange'));
+    });
+
+    expect(collapse).not.toHaveBeenCalled();
+    jest.restoreAllMocks();
+  });
 });

packages/react-aria/src/datepicker/useDateSegment.ts

@@ -264,7 +264,13 @@ export function useDateSegment(
     // Otherwise, when tapping on a segment in Android Chrome and then entering text,
     // composition events will be fired that break the DOM structure and crash the page.
     let selection = window.getSelection();
-    if (selection?.anchorNode && nodeContains(ref.current, selection?.anchorNode)) {
+    // Only collapse while focused, otherwise a stale anchor left in the segment (e.g. on Firefox)
+    // steals focus back into it on selectionchange. See #10259.
+    if (
+      selection?.anchorNode &&
+      nodeContains(ref.current, selection?.anchorNode) &&
+      getActiveElement() === ref.current
+    ) {
       selection.collapse(ref.current);
     }
   });