BU shows up multiple times on page

Problem/Motivation

BU will occasionally show up multiple times, especially in a sites front end. Here's a video: https://www.drupal.org/files/issues/2021-03-13/bu-dupe.mp4 →

Steps to reproduce

Install module, add #test-bu to url. Settings probably don't matter; I've included a .yml export → anyway.

Proposed resolution

If bu has already been attached to the page, skip further calls during Drupal.behaviors.bu::attach()

Attached is a patch for bu.js → and my patched version of bu.js →

Patch wraps normal execution with:

if(typeof settings.bu.hooked === 'undefined'){
   // window.$buoop = { ... document.body.appendChild(e);
   settings.bu.hooked = true;
}

Remaining tasks

N/A?

User interface changes

none

API changes

drupalSettings.bu adds flag; drupalSettings.bu.hooked

Data model changes

none