MDL-44141 Completion: System updates data during restore

The completion system has code which is supposed to prevent it
updating completion status while grades are being restored. This
code was a nasty hack and had not worked for some time. As a result
completion dates were restored incorrectly.

This commit implements a 'proper' way to find out if a restore is
currently running, replacing the previous hack.

backup/controller/restore_controller.class.php

@@ -59,6 +59,9 @@ class restore_controller extends backup implements loggable {
 
     protected $checksum; // Cache @checksumable results for lighter @is_checksum_correct() uses
 
+    /** @var int Number of restore_controllers that are currently executing */
+    protected static $executing = 0;
+
     /**
      *
      * @param string $tempdir Directory under tempdir/backup awaiting restore
@@ -312,7 +315,26 @@ class restore_controller extends backup implements loggable {
             $this->log('notifying plan about excluded activities by type', backup::LOG_DEBUG);
             $this->plan->set_excluding_activities();
         }
-        return $this->plan->execute();
+        self::$executing++;
+        try {
+            $this->plan->execute();
+        } catch (Exception $e) {
+            self::$executing--;
+            throw $e;
+        }
+        self::$executing--;
+    }
+
+    /**
+     * Checks whether restore is currently executing. Certain parts of code that
+     * is called during restore, but not directly part of the restore system, may
+     * need to behave differently during restore (e.g. do not bother resetting a
+     * cache because we know it will be reset at end of operation).
+     *
+     * @return bool True if any restore is currently executing
+     */
+    public static function is_executing() {
+        return self::$executing > 0;
     }
 
     /**

lib/grade/grade_grade.php

@@ -779,22 +779,21 @@ class grade_grade extends grade_object {
             unset($SESSION->gradescorecache[$this->itemid]);
         }
 
-        // Ignore during restore
-        // TODO There should be a proper way to determine when we are in restore
-        // so that this hack looking for a $restore global is not needed.
-        global $restore;
-        if (!empty($restore->backup_unique_code)) {
-            return;
-        }
-
         require_once($CFG->libdir.'/completionlib.php');
 
         // Bail out immediately if completion is not enabled for site (saves loading
-        // grade item below)
+        // grade item & requiring the restore stuff).
         if (!completion_info::is_enabled_for_site()) {
             return;
         }
 
+        // Ignore during restore, as completion data will be updated anyway and
+        // doing it now will result in incorrect dates (it will say they got the
+        // grade completion now, instead of the correct time).
+        if (class_exists('restore_controller', false) && restore_controller::is_executing()) {
+            return;
+        }
+
         // Load information about grade item
         $this->load_grade_item();