respect DISALLOW_FILE_MODS

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Load text-domain on-demand
 - Call `redis_object_cache_error` action before `wp_die()`
 - Don't try to define `WP_REDIS_PLUGIN_PATH` twice
+- Respect `file_mod_allowed` filter and `DISALLOW_FILE_MODS` constant
 - Renamed `.redis-write-test.tmp` test file to `object-cache.tmp`
 
 ## 2.4.4

includes/class-plugin.php

@@ -1361,6 +1361,19 @@ public function initialize_filesystem( $url, $silent = false ) {
         return true;
     }
 
+    /**
+     * Determines whether object cache file modifications are allowed.
+     *
+     * @return bool
+     */
+    function is_file_mod_allowed() {
+        return apply_filters(
+            'file_mod_allowed',
+            ! defined( 'DISALLOW_FILE_MODS' ) || ! DISALLOW_FILE_MODS,
+            'object_cache_dropin'
+        );
+    }
+
     /**
      * Test if we can write in the WP_CONTENT_DIR and modify the `object-cache.php` drop-in
      *
@@ -1370,6 +1383,10 @@ public function test_filesystem_writing() {
         /** @var \WP_Filesystem_Base $wp_filesystem */
         global $wp_filesystem;
 
+        if ( ! $this->is_file_mod_allowed() ) {
+            return new WP_Error( 'disallowed', __( 'File modifications are not allowed.', 'redis-cache' ) );
+        }
+
         if ( ! $this->initialize_filesystem( '', true ) ) {
             return new WP_Error( 'fs', __( 'Could not initialize filesystem.', 'redis-cache' ) );
         }