Changeset 60931 for trunk/src/wp-includes/class-wp-scripts.php

Timestamp:

10/14/2025 05:45:17 AM (3 months ago)

Author:

westonruter

Message:

Script Loader: Propagate fetchpriority from dependents to dependencies.

This introduces a "fetchpriority bumping" mechanism for both classic scripts (WP_Scripts) and script modules (WP_Script_Modules). When a script with a higher fetchpriority is enqueued, any of its dependencies will have their fetchpriority elevated to match that of the highest-priority dependent. This ensures that all assets in a critical dependency chain are loaded with the appropriate priority, preventing a high-priority script from being blocked by a low-priority dependency. This is similar to logic used in script loading strategies to ensure that a blocking dependent causes delayed (async/defer) dependencies to also become blocking. See #12009.

When a script's fetchpriority is escalated, its original, registered priority is added to the tag via a data-wp-fetchpriority attribute. This matches the addition of the data-wp-strategy parameter added when the resulting loading strategy does not match the original.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/9770.

Follow-up to [60704].

Props westonruter, jonsurrell.
Fixes #61734.

File:

• trunk/src/wp-includes/class-wp-scripts.php (modified) (4 diffs)

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

@@ -128 +128 @@
      *
      * @since 6.3.0
-     * @var array
+     * @var array<string, string[]>
      */
     private $dependents_map = array();
@@ -440 +440 @@
             $attr['data-wp-strategy'] = $intended_strategy;
         }
-        if ( isset( $obj->extra['fetchpriority'] ) && 'auto' !== $obj->extra['fetchpriority'] && $this->is_valid_fetchpriority( $obj->extra['fetchpriority'] ) ) {
-            $attr['fetchpriority'] = $obj->extra['fetchpriority'];
-        }
+
+        // Determine fetchpriority.
+        $original_fetchpriority = isset( $obj->extra['fetchpriority'] ) ? $obj->extra['fetchpriority'] : null;
+        if ( null === $original_fetchpriority || ! $this->is_valid_fetchpriority( $original_fetchpriority ) ) {
+            $original_fetchpriority = 'auto';
+        }
+        $actual_fetchpriority = $this->get_highest_fetchpriority_with_dependents( $handle );
+        if ( null === $actual_fetchpriority ) {
+            // If null, it's likely this script was not explicitly enqueued, so in this case use the original priority.
+            $actual_fetchpriority = $original_fetchpriority;
+        }
+        if ( is_string( $actual_fetchpriority ) && 'auto' !== $actual_fetchpriority ) {
+            $attr['fetchpriority'] = $actual_fetchpriority;
+        }
+        if ( $original_fetchpriority !== $actual_fetchpriority ) {
+            $attr['data-wp-fetchpriority'] = $original_fetchpriority;
+        }
+
         $tag  = $translations . $ie_conditional_prefix . $before_script;
         $tag .= wp_get_script_tag( $attr );
@@ -899 +914 @@
      * Gets all dependents of a script.
      *
+     * This is not recursive.
+     *
      * @since 6.3.0
      *
@@ -1050 +1067 @@
 
         return $eligible_strategies;
+    }
+
+    /**
+     * Gets the highest fetch priority for a given script and all of its dependent scripts.
+     *
+     * @since 6.9.0
+     * @see self::filter_eligible_strategies()
+     * @see WP_Script_Modules::get_highest_fetchpriority_with_dependents()
+     *
+     * @param string              $handle  Script module ID.
+     * @param array<string, true> $checked Optional. An array of already checked script handles, used to avoid recursive loops.
+     * @return string|null Highest fetch priority for the script and its dependents.
+     */
+    private function get_highest_fetchpriority_with_dependents( string $handle, array $checked = array() ): ?string {
+        // If there is a recursive dependency, return early.
+        if ( isset( $checked[ $handle ] ) ) {
+            return null;
+        }
+
+        // Mark this handle as checked to guard against infinite recursion.
+        $checked[ $handle ] = true;
+
+        // Abort if the script is not enqueued or a dependency of an enqueued script.
+        if ( ! $this->query( $handle, 'enqueued' ) ) {
+            return null;
+        }
+
+        $fetchpriority = $this->get_data( $handle, 'fetchpriority' );
+        if ( ! $this->is_valid_fetchpriority( $fetchpriority ) ) {
+            $fetchpriority = 'auto';
+        }
+
+        static $priorities   = array(
+            'low',
+            'auto',
+            'high',
+        );
+        $high_priority_index = count( $priorities ) - 1;
+
+        $highest_priority_index = (int) array_search( $fetchpriority, $priorities, true );
+        if ( $highest_priority_index !== $high_priority_index ) {
+            foreach ( $this->get_dependents( $handle ) as $dependent_handle ) {
+                $dependent_priority = $this->get_highest_fetchpriority_with_dependents( $dependent_handle, $checked );
+                if ( is_string( $dependent_priority ) ) {
+                    $highest_priority_index = max(
+                        $highest_priority_index,
+                        (int) array_search( $dependent_priority, $priorities, true )
+                    );
+                    if ( $highest_priority_index === $high_priority_index ) {
+                        break;
+                    }
+                }
+            }
+        }
+
+        return $priorities[ $highest_priority_index ];
     }