Infinite loop test theme

functions.php

<?php

add_action(
	'enqueue_block_editor_assets',
	function () {
		wp_enqueue_script(
			'title-checker-js',
			get_theme_file_uri( 'title-checker.js' ),
			[],
			null,
			true
		);
	}
);

index.php

<?php

// Nothing

style.css

/*
Theme Name: Infinite Loop Test Theme
*/

title-checker.js

const {
  i18n: { __ },
  plugins: {
    registerPlugin,
  },
  data: {
    useSelect,
    useDispatch,
  },
} = wp;

function TitleChecker() {
  const postTitle = useSelect((select) => select('core/editor').getEditedPostAttribute('title'));
  const titleIsOk = 0 < postTitle.length;

  const { lockPostSaving, unlockPostSaving } = useDispatch('core/editor');
  const { createWarningNotice, removeNotice } = useDispatch('core/notices');

  /**
   * If post title is empty, then lock post saving and display a warning notice
   * else release lock and remove notice.
   */
  if (! titleIsOk) {
    lockPostSaving('title-empty-lock');
    createWarningNotice(
      __('Please enter a headline before publishing.', 'my-textdomain'),
      { id: 'title-empty-lock', isDismissible: false },
    );
  } else {
    unlockPostSaving('title-empty-lock');
    removeNotice('title-empty-lock');
  }

  // On the site where this issue occurred, a <PluginPrePublishPanel> was rendered here.
  return null;
}

registerPlugin('empty-title-check', { render: TitleChecker });