Fix attachment page redirect for pretty permalink URLs

src/wp-includes/canonical.php

@@ -551,6 +551,9 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 
 	if ( is_attachment() && ! get_option( 'wp_attachment_pages_enabled' ) ) {
 		$attachment_id        = get_query_var( 'attachment_id' );
+		if ( ! $attachment_id ) {
+			$attachment_id = get_queried_object_id();
+		}
 		$attachment_post      = get_post( $attachment_id );
 		$attachment_parent_id = $attachment_post ? $attachment_post->post_parent : 0;
 		$attachment_url       = wp_get_attachment_url( $attachment_id );

tests/phpunit/tests/canonical/attachmentRedirect.php

@@ -0,0 +1,217 @@
+<?php
+
+/**
+ * Tests for attachment page redirect when wp_attachment_pages_enabled is disabled.
+ *
+ * @group canonical
+ * @group rewrite
+ * @group query
+ */
+class Tests_Canonical_AttachmentRedirect extends WP_Canonical_UnitTestCase {
+
+	/**
+	 * Attachment post objects and related fixtures.
+	 */
+	public static $unattached;
+	public static $public_parent;
+	public static $attached_to_public;
+	public static $private_parent;
+	public static $attached_to_private;
+	public static $draft_parent;
+	public static $attached_to_draft;
+	public static $editor_user;
+
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
+		self::$editor_user = $factory->user->create( array( 'role' => 'editor' ) );
+
+		// Unattached attachment.
+		self::$unattached = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'attachment',
+				'post_title'  => 'Unattached Image',
+				'post_name'   => 'unattached-image',
+				'post_status' => 'inherit',
+				'post_parent' => 0,
+			)
+		);
+		update_post_meta( self::$unattached->ID, '_wp_attached_file', '2025/01/unattached-image.jpg' );
+
+		// Attachment on a public post.
+		self::$public_parent = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'post',
+				'post_title'  => 'Public Post',
+				'post_name'   => 'public-post',
+				'post_status' => 'publish',
+			)
+		);
+
+		self::$attached_to_public = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'attachment',
+				'post_title'  => 'Public Attached Image',
+				'post_name'   => 'public-attached-image',
+				'post_status' => 'inherit',
+				'post_parent' => self::$public_parent->ID,
+			)
+		);
+		update_post_meta( self::$attached_to_public->ID, '_wp_attached_file', '2025/01/public-attached-image.jpg' );
+
+		// Attachment on a private post.
+		self::$private_parent = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'post',
+				'post_title'  => 'Private Post',
+				'post_name'   => 'private-post',
+				'post_status' => 'private',
+				'post_author' => self::$editor_user,
+			)
+		);
+
+		self::$attached_to_private = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'attachment',
+				'post_title'  => 'Private Attached Image',
+				'post_name'   => 'private-attached-image',
+				'post_status' => 'inherit',
+				'post_parent' => self::$private_parent->ID,
+			)
+		);
+		update_post_meta( self::$attached_to_private->ID, '_wp_attached_file', '2025/01/private-attached-image.jpg' );
+
+		// Attachment on a draft post.
+		self::$draft_parent = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'post',
+				'post_title'  => 'Draft Post',
+				'post_name'   => 'draft-post',
+				'post_status' => 'draft',
+				'post_author' => self::$editor_user,
+			)
+		);
+
+		self::$attached_to_draft = $factory->post->create_and_get(
+			array(
+				'post_type'   => 'attachment',
+				'post_title'  => 'Draft Attached Image',
+				'post_name'   => 'draft-attached-image',
+				'post_status' => 'inherit',
+				'post_parent' => self::$draft_parent->ID,
+			)
+		);
+		update_post_meta( self::$attached_to_draft->ID, '_wp_attached_file', '2025/01/draft-attached-image.jpg' );
+	}
+
+	/**
+	 * Helper to get the expected redirect path for an attachment.
+	 */
+	private function get_expected_path( $attachment_id ) {
+		return parse_url( wp_get_attachment_url( $attachment_id ), PHP_URL_PATH );
+	}
+
+	// -------------------------------------------------------------------------
+	// Unattached attachment tests.
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Pretty permalink slug-based attachment URLs should redirect to the file URL
+	 * when wp_attachment_pages_enabled is 0.
+	 *
+	 * This is the primary regression test: get_query_var( 'attachment_id' ) is only
+	 * populated for ?attachment_id=123 URLs, not slug-based URLs. The fix falls back
+	 * to get_queried_object_id().
+	 */
+	public function test_unattached_slug_url_redirects_when_pages_disabled() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+
+		$this->assertCanonical( '/unattached-image/', $this->get_expected_path( self::$unattached->ID ) );
+	}
+
+	/**
+	 * Query string ?attachment_id=ID should also redirect when pages are disabled.
+	 */
+	public function test_unattached_query_var_url_redirects_when_pages_disabled() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+
+		$this->assertCanonical( '/?attachment_id=' . self::$unattached->ID, $this->get_expected_path( self::$unattached->ID ) );
+	}
+
+	// -------------------------------------------------------------------------
+	// Attached to a public post.
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Attachment on a public post should redirect via its child slug URL.
+	 *
+	 * With pretty permalinks, child attachment URLs take the form
+	 * /parent-slug/attachment-slug/.
+	 */
+	public function test_attached_to_public_post_slug_url_redirects() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+
+		$this->assertCanonical( '/public-post/public-attached-image/', $this->get_expected_path( self::$attached_to_public->ID ) );
+	}
+
+	// -------------------------------------------------------------------------
+	// Attached to a private post — logged out (should NOT redirect).
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Attachment on a private post should not redirect for anonymous users,
+	 * to avoid leaking the file URL.
+	 */
+	public function test_attached_to_private_post_no_redirect_for_anonymous() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+		wp_set_current_user( 0 );
+
+		$this->assertCanonical( '/private-post/private-attached-image/', '/private-post/private-attached-image/' );
+	}
+
+	// -------------------------------------------------------------------------
+	// Attached to a private post — authorized user (should redirect).
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Attachment on a private post should redirect for a user who can read it.
+	 */
+	public function test_attached_to_private_post_redirects_for_authorized_user() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+		wp_set_current_user( self::$editor_user );
+
+		$this->assertCanonical( '/private-post/private-attached-image/', $this->get_expected_path( self::$attached_to_private->ID ) );
+	}
+
+	// -------------------------------------------------------------------------
+	// Attached to a draft post (should NOT redirect).
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Attachment on a draft post should not redirect for anonymous users.
+	 */
+	public function test_attached_to_draft_post_no_redirect_for_anonymous() {
+		update_option( 'wp_attachment_pages_enabled', 0 );
+		$this->set_permalink_structure( '/%postname%/' );
+		wp_set_current_user( 0 );
+
+		$this->assertCanonical( '/draft-post/draft-attached-image/', '/draft-post/draft-attached-image/' );
+	}
+
+	// -------------------------------------------------------------------------
+	// Pages enabled — should NOT redirect.
+	// -------------------------------------------------------------------------
+
+	/**
+	 * When attachment pages are enabled, slug URLs should not redirect to the file.
+	 */
+	public function test_no_redirect_when_attachment_pages_enabled() {
+		update_option( 'wp_attachment_pages_enabled', 1 );
+		$this->set_permalink_structure( '/%postname%/' );
+
+		$this->assertCanonical( '/unattached-image/', '/unattached-image/' );
+	}
+}