Pre-Publish Warning for Images Without Alt Text

add_action( 'enqueue_block_editor_assets', function () {
    wp_register_script( 'wpide-alt-check', '', array( 'wp-plugins', 'wp-editor', 'wp-element', 'wp-data', 'wp-components', 'wp-block-editor' ), null, true );
    wp_enqueue_script( 'wpide-alt-check' );
    wp_add_inline_script( 'wpide-alt-check', <<<'JS'
(function (wp) {
    var el = wp.element.createElement;
    var Panel = (wp.editor && wp.editor.PluginPrePublishPanel) || (wp.editPost && wp.editPost.PluginPrePublishPanel);
    if (!Panel) { return; }
    function collect(blocks, out) {
        blocks.forEach(function (b) {
            if ((b.name === 'core/image' || b.name === 'core/media-text' || b.name === 'core/cover') && !(b.attributes.alt || '').trim() && (b.attributes.url || b.attributes.mediaUrl)) {
                out.push(b);
            }
            if (b.innerBlocks && b.innerBlocks.length) { collect(b.innerBlocks, out); }
        });
        return out;
    }
    function AltPanel() {
        var missing = wp.data.useSelect(function (select) { return collect(select('core/block-editor').getBlocks(), []); }, []);
        var select = wp.data.useDispatch('core/block-editor').selectBlock;
        return el(Panel, { title: 'Image alt text', initialOpen: missing.length > 0 },
            missing.length === 0 ? el('p', null, 'Every image has alternative text.') :
            el('div', null,
                el('p', null, missing.length + ' image(s) have no alternative text:'),
                missing.map(function (b, i) {
                    return el(wp.components.Button, { key: b.clientId, variant: 'link', onClick: function () { select(b.clientId); } }, 'Image ' + (i + 1));
                })
            )
        );
    }
    wp.plugins.registerPlugin('wpide-alt-check', { render: AltPanel });
})(window.wp);
JS
    );
} );