Bug: [lexical-y] A collaborator's bold on a word right after a bold node is lost when another client remakes the line with several words changed #9646

/**
 * 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,
  $createTextNode,
  $getRoot,
  $setSelection,
  type ElementNode,
} from 'lexical';
import {describe, expect, test} from 'vitest';

import {freshReader, type Peer, setup} from '../utils/harness';

const $line = () => $getRoot().getChildAtIndex(1) as ElementNode;
const bold = (p: Peer) =>
  p.read(() =>
    $line()
      .getAllTextNodes()
      .filter(n => n.hasFormat('bold'))
      .map(n => n.getTextContent())
      .join('|'),
  );
const text = (p: Peer) => p.read(() => $line().getTextContent());

const CASES = [
  {
    made: ['t490z t169z.  t611z. t167z'],
    old: [['t552z, t860z t701z ', true], ['t167z', false]] as [string, boolean][],
    victim: 't167z',
  },
  {
    made: ['t477z.  t7', '82z'],
    old: [['t168z t435z  ', true], ['t782z t194z', false]] as [string, boolean][],
    victim: 't782z',
  },
  {
    // control: the node before the word is plain
    made: ['t490z t169z.  t611z. t167z'],
    old: [['t552z, t860z t701z ', false], ['t167z', false]] as [string, boolean][],
    victim: 't167z',
  },
];

describe('a bold on an unchanged word, concurrent with a remake of its line', () => {
  for (const [i, c] of CASES.entries()) {
    for (const ids of [
      [1, 2],
      [2, 1],
    ]) {
      test(`case ${i} (${c.old[0][1] ? 'bold first node' : 'control: plain first node'}), ids ${ids}`, async () => {
        const t = await setup(
          () => {
            $getRoot().append(
              $createParagraphNode().append($createTextNode('Title')),
              $createParagraphNode().append(
                ...c.old.map(([s, b]) => {
                  const n = $createTextNode(s);
                  return b ? n.toggleFormat('bold') : n;
                }),
              ),
            );
          },
          {ids},
        );
        t.offline();
        t.a.update(() => {
          for (const o of $line().getChildren()) {
            o.remove();
          }
          $line().append(...c.made.map(s => $createTextNode(s)));
          $setSelection(null);
        });
        t.b.update(() => {
          const old = c.old.map(([s]) => s).join('');
          const vAt = old.indexOf(c.victim);
          let acc = 0;
          for (const leaf of $line().getAllTextNodes()) {
            const size = leaf.getTextContentSize();
            const s0 = Math.max(vAt, acc);
            const s1 = Math.min(vAt + c.victim.length, acc + size);
            if (s1 > s0) {
              const parts = leaf.splitText(s0 - acc, s1 - acc);
              const mid = s0 - acc === 0 ? parts[0] : parts[1];
              if (!mid.hasFormat('bold')) {
                mid.toggleFormat('bold');
              }
            }
            acc += size;
          }
          $setSelection(null);
        });
        await t.sync();
        const fresh = await freshReader(t.a);
        expect(text(t.a)).toBe(c.made.join(''));
        expect(text(t.b)).toBe(text(t.a));
        expect(text(fresh)).toBe(text(t.a));
        for (const p of [t.a, t.b, fresh]) {
          expect(bold(p)).toBe(c.victim);
        }
      });
    }
  }
});