Sharing Service: Make sure we only check for legacy sharing buttons i…

…mplementation on non-block themes (#39349)

* make sure we only check for legacy sharing buttons implementation on non-block themes

* changelog

* Omit the function exists check

projects/plugins/jetpack/changelog/update-sharing-services-assets-only-on-old-themes

@@ -0,0 +1,4 @@
+Significance: major
+Type: compat
+
+Improved compatibiliy with modern block themes by not checking whether we should use legacy sharing buttons mechanism

projects/plugins/jetpack/modules/sharedaddy/sharing-service.php

@@ -898,6 +898,10 @@ class_exists( 'Jetpack_AMP_Support' )
  * @return void
  */
 function sharing_add_header() {
+	if ( ! sharing_should_load_legacy_sharing_buttons() ) {
+		return;
+	}
+
 	$sharer  = new Sharing_Service();
 	$enabled = $sharer->get_blog_services();
 
@@ -912,6 +916,20 @@ function sharing_add_header() {
 }
 add_action( 'wp_head', 'sharing_add_header', 1 );
 
+/**
+ * Determine if legacy sharing buttons should be loaded.
+ * Do this by checking if the current theme is a block theme
+ * If it is, we shouldn't enqueue the sharing assets
+ * as the recommended way of adding sharing buttons is via the editor.
+ *
+ * @since $$next-version$$
+ *
+ * @return bool True if legacy sharing buttons should be loaded, false otherwise.
+ */
+function sharing_should_load_legacy_sharing_buttons() {
+	return ! wp_is_block_theme();
+}
+
 /**
  * Launch sharing requests on page load when a specific query string is used.
  *