Boost: Disable defer JS in Divi builder

projects/plugins/boost/changelog/add-divi-compat

@@ -0,0 +1,4 @@
+Significance: patch
+Type: added
+
+Compatibility: Added compatibility with divi builder and Deferred JS.

projects/plugins/boost/compatibility/divi.php

@@ -0,0 +1,43 @@
+<?php
+/**
+ * Compatibility functions for Divi Builder
+ *
+ * @package automattic/jetpack-boost
+ */
+
+namespace Automattic\Jetpack_Boost\Compatibility\Divi;
+
+/**
+ * Defer JS can break Divi Builder.
+ */
+function disable_defer_js_for_divi_builder( $should_defer_js ) {
+	$is_divi_builder = filter_input( INPUT_GET, 'et_fb', FILTER_VALIDATE_INT );
+
+	if ( 1 === (int) $is_divi_builder ) {
+		return false;
+	}
+
+	$is_divi_preview = filter_input(
+		INPUT_GET,
+		'et_pb_preview',
+		FILTER_VALIDATE_BOOLEAN,
+		array(
+			'flags' => FILTER_NULL_ON_FAILURE,
+		)
+	);
+
+	if ( true === $is_divi_preview ) {
+		return false;
+	}
+
+	if ( function_exists( 'is_et_pb_preview' ) ) {
+		/** @phan-suppress-next-line PhanUndeclaredFunction */
+		if ( \is_et_pb_preview() ) {
+			return false;
+		}
+	}
+
+	return $should_defer_js;
+}
+
+add_filter( 'jetpack_boost_should_defer_js', __NAMESPACE__ . '\disable_defer_js_for_divi_builder' );

projects/plugins/boost/jetpack-boost.php

@@ -251,6 +251,9 @@ function include_compatibility_files() {
 		require_once __DIR__ . '/compatibility/breakdance.php';
 	}
 
+	// Compatibility with Divi by Elegant Themes.
+	require_once __DIR__ . '/compatibility/divi.php';
+
 	// Exclude known scripts that causes problem when concatenated.
 	require_once __DIR__ . '/compatibility/js-concatenate.php';