Ticket #59599: 58599.diff

src/wp-includes/class-wp-scripts.php

@@ -281 +281 @@
                         $intended_strategy = '';
                 }
 
+                // If the script is in the header group, current output is the header, the intended strategy is `defer`, the
+                // actual strategy is not defer and all dependent scripts are in the footer - move this script to the footer.
+                if ( 'defer' === $intended_strategy && 'defer' !== $strategy && 0 === $this->groups[ $handle ] && 0 === $group ) {
+                        // Check that all depedencies are in the footer.
+                        $all_deps_in_footer = true;
+                        foreach ( $this->get_dependents( $handle ) as $dep ) {
+                                if ( isset( $this->groups[ $dep ] ) && 1 !== $this->groups[ $dep ] ) {
+                                        $all_deps_in_footer = false;
+                                        break;
+                                }
+                        }
+                        if ( $all_deps_in_footer ) {
+                                $this->in_footer[] = $handle;
+                                $this->groups[ $handle ] = 1;
+                                return;
+                        }
+                }
+
                 if ( $conditional ) {
                         $cond_before = "<!--[if {$conditional}]>\n";
                         $cond_after  = "<![endif]-->\n";