WP Super Cache: don't serve a cached page when a POST request is made…

… (#36211)

* Check for DONOTCACHEPAGE in postload function

This is the entry for creating cache pages, and serving cache files
in late init.

* Define DONOTCACHEPAGE when caching is disabled early on

* Separate out this check to make logging better.

* Define DONOTCACHEPAGE so postload function doesn't serve a cached
  page.

* changelog

---------

Co-authored-by: Peter Petrov <[email protected]>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/8174387724

CHANGELOG.md

@@ -32,6 +32,7 @@ This is an alpha version! The changes listed here are not final.
 - WP Super Cache - fix the wp_super_cache_clear_post_cache so the homepage cache isn't deleted too.
 - WP Super Cache: bail if the request uri isn't set. It means the plugin isn't configured yet.
 - WP Super Cache: don't create an output buffer if there's already one active
+- WP Super Cache: fixed serving a cached page on POST with late init enabled.
 - WP Super Cache: fix the output buffer check, and make debug logs pre-formatted.
 
 ## [1.11.0] - 2023-11-08

wp-cache-phase1.php

@@ -109,6 +109,7 @@
 
 // don't cache in wp-admin
 if ( wpsc_is_backend() ) {
+	define( 'DONOTCACHEPAGE', 1 );
 	return true;
 }
 
@@ -122,6 +123,7 @@
 
 if ( wpsc_is_caching_user_disabled() ) {
 	wp_cache_debug( 'Caching disabled for logged in users on settings page.' );
+	define( 'DONOTCACHEPAGE', 1 );
 	return true;
 }
 
@@ -133,8 +135,20 @@
 // an init action wpsc plugins can hook on to.
 do_cacheaction( 'cache_init' );
 
+if ( ! $cache_enabled ) {
+	return true;
+}
+
 // don't cache or serve cached files for various URLs, including the Customizer.
-if ( ! $cache_enabled || ( isset( $_SERVER['REQUEST_METHOD'] ) && in_array( $_SERVER['REQUEST_METHOD'], array( 'POST', 'PUT', 'DELETE' ) ) ) || isset( $_GET['customize_changeset_uuid'] ) ) {
+if ( isset( $_SERVER['REQUEST_METHOD'] ) && in_array( $_SERVER['REQUEST_METHOD'], array( 'POST', 'PUT', 'DELETE' ), true ) ) {
+	wp_cache_debug( 'Caching disabled for non GET request.' );
+	define( 'DONOTCACHEPAGE', 1 );
+	return true;
+}
+
+if ( isset( $_GET['customize_changeset_uuid'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
+	wp_cache_debug( 'Caching disabled for customizer.' );
+	define( 'DONOTCACHEPAGE', 1 );
 	return true;
 }
 

wp-cache-phase2.php

@@ -390,6 +390,11 @@ function wp_cache_postload() {
 	global $cache_enabled, $wp_super_cache_late_init;
 	global $wp_cache_request_uri;
 
+	if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
+		wp_cache_debug( 'wp_cache_postload: DONOTCACHEPAGE defined. Not running.' );
+		return false;
+	}
+
 	if ( empty( $wp_cache_request_uri ) ) {
 		wp_cache_debug( 'wp_cache_postload: no request uri configured. Not running.' );
 		return false;