Bug: [lexical-y] A programmatic selection inside an emoji either throws or leaves the author with text no other client has #9701

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 */

// @vitest-environment node

import {
  $createParagraphNode,
  $createRangeSelection,
  $createTextNode,
  $getRoot,
  $setSelection,
  type TextNode,
} from 'lexical';
import {expect, test} from 'vitest';

import {expectConverged, setup} from '../utils/harness';

// "ab😀cd": the emoji is the UTF-16 pair at offsets 2 and 3.
const cases: [string, number, number, 'bold' | 'insert' | 'delete'][] = [
  ['bold a range that ends inside the emoji', 0, 3, 'bold'],
  ['bold a range that starts inside the emoji', 3, 6, 'bold'],
  ['type inside the emoji', 3, 3, 'insert'],
  ['delete half of the emoji', 2, 3, 'delete'],
];
for (const [name, anchor, focus, kind] of cases) {
  test(name, async () => {
    const t = await setup(() =>
      $getRoot().append(
        $createParagraphNode().append($createTextNode('ab\u{1F600}cd')),
      ),
    );
    t.b.update(() => {
      const n = $getRoot().getFirstDescendant() as TextNode;
      const s = $createRangeSelection();
      s.anchor.set(n.getKey(), anchor, 'text');
      s.focus.set(n.getKey(), focus, 'text');
      $setSelection(s);
      if (kind === 'bold') {
        s.formatText('bold');
      } else if (kind === 'insert') {
        s.insertText('X');
      } else {
        s.removeText();
      }
      $setSelection(null);
    });
    await t.sync();
    // Expected: one consistent outcome (the range clamped to the emoji, or
    // the update refused), and every client showing the same text.
    await expectConverged(t.peers);
    expect(t.b.warnings).toEqual([]);
  });
}