Hooks: Fix resort_active_iterations() skipping next priority on self-removal by mrcasual · Pull Request #10949 · WordPress/wordpress-develop

mrcasual · 2026-02-17T00:31:20Z

Trac ticket: https://core.trac.wordpress.org/ticket/64653

When a callback removes itself during do_action() / apply_filters() and is the sole callback at its priority, resort_active_iterations() positions the internal array pointer one step too far. The main loop's next() call then skips the following priority entirely.

Steps to reproduce

<?php

add_action( 'test_hook', '__return_true', 10 );

add_action( 'test_hook', function () {
    remove_action( 'test_hook', __FUNCTION__, 50 );
}, 50 );

add_action( 'test_hook', function () {
    error_log( 'This never runs' );
}, 100 );

do_action( 'test_hook' ); // Priority 100 is silently skipped.

The bug requires: (1) a lower priority exists, (2) the removed callback is the only one at its priority.

github-actions · 2026-02-17T00:31:29Z

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Props mrcasual, westonruter.

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github-actions · 2026-02-17T00:46:05Z

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westonruter · 2026-02-17T06:42:43Z

+	 *
+	 * @ticket 64653
+	 */
+	public function test_self_removing_callback_does_not_skip_next_priority() {


I can confirm this test fails without the fix applied:

1) Tests_Hooks_DoAction::test_self_removing_callback_does_not_skip_next_priority Priority 100 should not be skipped when priority 50 removes itself during iteration. Failed asserting that two arrays are identical. --- Expected +++ Actual @@ @@ Array &0 ( 0 => 10 1 => 50 - 2 => 100 ) /var/www/tests/phpunit/tests/hooks/doAction.php:331

westonruter · 2026-02-17T06:42:57Z

+	 *
+	 * @ticket 64653
+	 */
+	public function test_self_removing_callback_at_lowest_priority() {


This test does not fail without the fix applied.

This test does not fail without the fix applied.

Yup, that's expected. This test covers the edge case where the self-removing callback is at the lowest priority, which takes a different code path in resort_active_iterations() that already worked correctly. I included it as a regression guard since there was no coverage for that path if it's ever refactored.

…f-removal. When a callback removes itself during `do_action()`/`apply_filters()` and is the sole callback at its priority, `resort_active_iterations()` repositions the internal array pointer one position too far. The main loop's `next()` call then skips the following priority entirely. The fix detects when the current priority was removed (the pointer advanced past it) and calls `prev()` so that `next()` in the calling loop lands on the correct priority. Fixes #64653.

mrcasual · 2026-03-26T01:46:10Z

@westonruter, what's the process for moving this forward?

westonruter · 2026-03-26T18:38:56Z

@mrcasual Once the 7.0 branch is made and trunk is open for commits, we can move this forward for WordPress 7.1.

Copilot

Pull request overview

Fixes a WP_Hook iteration bug where removing the only callback at the current priority during do_action() / apply_filters() could cause the next priority to be skipped due to an off-by-one internal pointer reposition in resort_active_iterations().

Changes:

Adjust WP_Hook::resort_active_iterations() to step the iteration pointer back when the current priority was removed, so the main loop’s next() lands on the correct next priority.
Add PHPUnit regression tests covering self-removal at a middle priority and at the lowest priority during do_action().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
`src/wp-includes/class-wp-hook.php`	Fixes pointer repositioning in `resort_active_iterations()` when the current priority is removed mid-iteration.
`tests/phpunit/tests/hooks/doAction.php`	Adds regression tests to ensure self-removal does not skip subsequent priorities during actions.

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Copilot · 2026-03-26T18:43:22Z

+	public function test_self_removing_callback_does_not_skip_next_priority() {
+		$hook      = new WP_Hook();
+		$hook_name = __FUNCTION__;
+		$log       = array();
+
+		$callback_10 = function () use ( &$log ) {
+			$log[] = 10;
+		};
+
+		// Callback that removes itself -- the only callback at priority 50.
+		$self_removing = function () use ( &$log, &$self_removing, $hook, $hook_name ) {
+			$hook->remove_filter( $hook_name, $self_removing, 50 );
+			$log[] = 50;
+		};
+
+		$callback_100 = function () use ( &$log ) {
+			$log[] = 100;
+		};
+
+		$hook->add_filter( $hook_name, $callback_10, 10, 0 );
+		$hook->add_filter( $hook_name, $self_removing, 50, 0 );
+		$hook->add_filter( $hook_name, $callback_100, 100, 0 );
+
+		$hook->do_action( array() );
+
+		$this->assertSame( array( 10, 50, 100 ), $log, 'Priority 100 should not be skipped when priority 50 removes itself during iteration.' );
+	}


The regression tests added here cover the do_action() path, but the PR description indicates the bug also affects apply_filters(). Consider adding an equivalent test in tests/phpunit/tests/hooks/applyFilters.php to ensure the behavior is covered when $this->doing_action is false (different argument handling) and to prevent future regressions specific to apply_filters().

The doing_action flag only affects argument threading at line 338 ($args[0] = $value) - it's never read by resort_active_iterations(). Both do_action() and apply_filters() share the same iteration loop, so these tests already cover both paths. The pointer arithmetic is identical regardless of entry point.

mrcasual force-pushed the fix/wp-hook-resort-active-iterations-skip branch from 90f0d19 to 40ea968 Compare February 17, 2026 00:33

westonruter reviewed Feb 17, 2026

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mrcasual force-pushed the fix/wp-hook-resort-active-iterations-skip branch from 40ea968 to 9ca834c Compare February 20, 2026 16:08

westonruter requested a review from Copilot March 26, 2026 18:38

Copilot started reviewing on behalf of westonruter March 26, 2026 18:39 View session

Copilot AI reviewed Mar 26, 2026

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mrcasual mentioned this pull request Apr 10, 2026

Hooks: Fix pointer over-advance in resort_active_iterations() #11510

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Hooks: Fix resort_active_iterations() skipping next priority on self-removal #10949

Hooks: Fix resort_active_iterations() skipping next priority on self-removal #10949
mrcasual wants to merge 1 commit intoWordPress:trunkfrom
mrcasual:fix/wp-hook-resort-active-iterations-skip

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