InnerBlocks and empty $block in render_block_preview action

• pe-pe

• August 7, 2025 at 7:16 pm

Hi!
I noticed a problem when I create custom blocks that contain <InnerBlocks/>. In that case, I am not able to retrieve the $block object in the js script fired in the backend.

function.php
——————

add_action('init', 'register_acf_blocks');
function register_acf_blocks() {
	wp_register_script('accordion-script', get_stylesheet_directory_uri() . '/blocks/accordion/script.js');
	register_block_type(get_template_directory() . '/blocks/accordion/block.json');
}

block.json
————–

{
    "name": "accordion",
    "title": "Accordion",
    "description": "Accordion to hide large amounts of text in drop-down sections.",
    "category": "my-category",
    "icon": "media-code",
    "keywords": [
        "accordion"
    ],
    "acf": {
        "mode": "preview",
        "renderTemplate": "render.php"
    },
	"script": "accordion-script",
    "supports": {
        "layout": false,
        "align": false,
        "customClassName": false
    },
    "example": {
        "viewportWidth": 800
    }
}

render.php
—————-
<InnerBlocks/>

script.js
———–

(function($){

    var initializeBlock = function($block) {
		console.log($block); // HERE IS THE PROBLEM!!! IN CONSOLE: e.<computed> {length: 0, prevObject: e.<computed>}
    }

    if( window.acf ) {
        window.acf.addAction( 'render_block_preview/type=accordion', initializeBlock );
    }

})(jQuery);

The problem disappears when I insert any HTML instead of InnerBlocks in render.php

WP version: 6.8.1
ACF version 6.4.2