[WordPress][WP Rocket] Barely tested hack to exclude a file from defer JS only, without having to exclude it from minification.

wp-rocket-exclude-from-defer-only.php

<?php
/**
 * WP Rocket: 
 * 1. Customise order of minification and defer operations.
 * 2. Exclude file from defer JS only (still minified).
 * 
 * Tested rudimentary with WP Rocket 2.11.7 and 3.0.x.
 * Test before using this in production!
 */
add_action( 'wp_rocket_loaded', function () {

	// Remove default minify/defer priorities.
	remove_filter( 'rocket_buffer', 'rocket_minify_process', 13 );
	remove_filter( 'rocket_buffer', 'rocket_defer_js', 14 );

	// Re-add minify/defer priorities (reversed).
	add_filter( 'rocket_buffer', 'rocket_defer_js', 13 );
	add_filter( 'rocket_buffer', 'rocket_minify_process', 14 );

	// Exclude file from defer JS.
	add_filter( 'rocket_exclude_defer_js', function ( $excluded_files = [] ) {

		// Use original, not modified path to file!
		$excluded_files[] = '/wp-content/original/path/to/file.js';

		return $excluded_files;
	} );
});