From 2fa8aea27987db2669a37b776e39342433282b87 Mon Sep 17 00:00:00 2001
From: David Mudrak <david@moodle.com>
Date: Thu, 7 Jun 2012 16:29:09 +0200
Subject: [PATCH] MDL-33587 Throw coding exception when trying to unlink a
 non-reference file

---
 lib/filestorage/stored_file.php | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/filestorage/stored_file.php b/lib/filestorage/stored_file.php
index 75ab48312a2..3041a52a228 100644
--- a/lib/filestorage/stored_file.php
+++ b/lib/filestorage/stored_file.php
@@ -196,12 +196,19 @@ class stored_file {
     }
 
     /**
-     * Delete file reference
+     * Unlink the stored file from the referenced file
      *
+     * This methods destroys the link to the record in files_reference table. This effectively
+     * turns the stored file from being an alias to a plain copy. However, the caller has
+     * to make sure that the actual file's content has beed synced prior to calling this method.
      */
     public function delete_reference() {
         global $DB;
 
+        if (!$this->is_external_file()) {
+            throw new coding_exception('An attempt to unlink a non-reference file.');
+        }
+
         // Remove repository info.
         $this->repository = null;