Changeset 61176

Timestamp:

11/07/2025 06:11:24 AM (2 weeks ago)

Author:

westonruter

Message:

Script Loader: Guard against exponential recursion during calculation of loading strategy and fetchpriority.

This addresses a performance issue in the recursive WP_Scripts::get_highest_fetchpriority_with_dependents() and WP_Scripts::filter_eligible_strategies() methods for redundant processing of shared dependencies in complex dependency graphs. To fix this, a $stored_results param is introduced which is passed by reference; this variable contains a cache of the calculated results for all scripts handles, so that subsequent calls for the same handle can return the cached value instead of re-computing it.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/10459

Follow-up to [60704], [60931], [56033].

Props ciobanucatalin, b1ink0, westonruter, mukesh27.
See #61734, #12009.
Fixes #64194.

Location:

trunk

Files:

• src/wp-includes/class-wp-scripts.php (modified) (5 diffs)
• tests/phpunit/tests/dependencies/scripts.php (modified) (2 diffs)

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

@@ -998 +998 @@
      * @since 6.3.0
      *
-     * @param string              $handle              The script handle.
-     * @param string[]|null       $eligible_strategies Optional. The list of strategies to filter. Default null.
-     * @param array<string, true> $checked             Optional. An array of already checked script handles, used to avoid recursive loops.
+     * @param string                  $handle              The script handle.
+     * @param string[]|null           $eligible_strategies Optional. The list of strategies to filter. Default null.
+     * @param array<string, true>     $checked             Optional. An array of already checked script handles, used to avoid recursive loops.
+     * @param array<string, string[]> $stored_results      Optional. An array of already computed eligible loading strategies by handle, used to increase performance in large dependency lists.
      * @return string[] A list of eligible loading strategies that could be used.
      */
-    private function filter_eligible_strategies( $handle, $eligible_strategies = null, $checked = array() ) {
+    private function filter_eligible_strategies( $handle, $eligible_strategies = null, $checked = array(), array &$stored_results = array() ) {
+        if ( isset( $stored_results[ $handle ] ) ) {
+            return $stored_results[ $handle ];
+        }
+
         // If no strategies are being passed, all strategies are eligible.
         if ( null === $eligible_strategies ) {
@@ -1054 +1059 @@
             }
 
-            $eligible_strategies = $this->filter_eligible_strategies( $dependent, $eligible_strategies, $checked );
-        }
-
+            $eligible_strategies = $this->filter_eligible_strategies( $dependent, $eligible_strategies, $checked, $stored_results );
+        }
+        $stored_results[ $handle ] = $eligible_strategies;
         return $eligible_strategies;
     }
@@ -1067 +1072 @@
      * @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.
+     * @param string                $handle         Script module ID.
+     * @param array<string, true>   $checked        Optional. An array of already checked script handles, used to avoid recursive loops.
+     * @param array<string, string> $stored_results Optional. An array of already computed max priority by handle, used to increase performance in large dependency lists.
      * @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 {
+    private function get_highest_fetchpriority_with_dependents( string $handle, array $checked = array(), array &$stored_results = array() ): ?string {
+        if ( isset( $stored_results[ $handle ] ) ) {
+            return $stored_results[ $handle ];
+        }
+
         // If there is a recursive dependency, return early.
         if ( isset( $checked[ $handle ] ) ) {
@@ -1100 +1110 @@
         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 );
+                $dependent_priority = $this->get_highest_fetchpriority_with_dependents( $dependent_handle, $checked, $stored_results );
                 if ( is_string( $dependent_priority ) ) {
                     $highest_priority_index = max(
@@ -1112 +1122 @@
             }
         }
-
+        $stored_results[ $handle ] = $priorities[ $highest_priority_index ]; // @phpstan-ignore parameterByRef.type (We know the index is valid and that this will be a string.)
         return $priorities[ $highest_priority_index ];
     }

trunk/tests/phpunit/tests/dependencies/scripts.php

@@ -1437 +1437 @@
 
     /**
+     * Tests that `WP_Scripts::get_highest_fetchpriority_with_dependents()` correctly reuses cached results.
+     *
+     * @ticket 64194
+     *
+     * @covers WP_Scripts::get_highest_fetchpriority_with_dependents
+     */
+    public function test_highest_fetchpriority_with_dependents_uses_cached_result() {
+        $wp_scripts = new WP_Scripts();
+        $wp_scripts->add( 'd', 'https://example.com/d.js' );
+        $wp_scripts->add_data( 'd', 'fetchpriority', 'low' );
+
+        /*
+         * Simulate a pre-existing `$stored_results` cache entry for `d`.
+         * If the caching logic works, the function should use this "high" value
+         * instead of recalculating based on the actual (lower) value.
+         */
+        $stored_results = array( 'd' => 'high' );
+
+        // Access the private method using reflection.
+        $method = new ReflectionMethod( WP_Scripts::class, 'get_highest_fetchpriority_with_dependents' );
+        if ( PHP_VERSION_ID < 80100 ) {
+            $method->setAccessible( true );
+        }
+
+        // Pass `$stored_results` BY REFERENCE.
+        $result = $method->invokeArgs( $wp_scripts, array( 'd', array(), &$stored_results ) );
+
+        $this->assertSame(
+            'high',
+            $result,
+            'Expected "high" indicates that the cached `$stored_results` entry for D was used instead of recalculating.'
+        );
+    }
+
+    /**
      * Tests that printing a script without enqueueing has the same output as when it is enqueued.
      *
@@ -1533 +1568 @@
         $expected = str_replace( "'", '"', $expected );
         $this->assertSame( $expected, $output, 'Scripts registered with no strategy assigned, and who have no dependencies, should have no loading strategy attributes printed.' );
+    }
+
+    /**
+     * Tests that `WP_Scripts::filter_eligible_strategies()` correctly reuses cached results.
+     *
+     * @ticket 64194
+     *
+     * @covers WP_Scripts::filter_eligible_strategies
+     */
+    public function test_filter_eligible_strategies_uses_cached_result() {
+        $wp_scripts = new WP_Scripts();
+        $wp_scripts->add( 'd', 'https://example.com/d.js' );
+        $wp_scripts->add_data( 'd', 'strategy', 'defer' );
+
+        /*
+         * Simulate a cached result in `$stored_results` for D.
+         * If caching logic is functioning properly, this cached value
+         * should be returned immediately without recomputing.
+         */
+        $stored_results = array( 'd' => array( 'async' ) );
+
+        // Access the private method via reflection.
+        $method = new ReflectionMethod( WP_Scripts::class, 'filter_eligible_strategies' );
+        if ( PHP_VERSION_ID < 80100 ) {
+            $method->setAccessible( true );
+        }
+
+        // Invoke the method with `$stored_results` passed by reference.
+        $result = $method->invokeArgs( $wp_scripts, array( 'd', null, array(), &$stored_results ) );
+
+        $this->assertSame(
+            array( 'async' ),
+            $result,
+            'Expected cached `$stored_results` value for D to be reused instead of recomputed.'
+        );
     }