MDL-18177 availability: Excluding group members availability info

If setting was not enabled when backing up, exclude the availability
information of group members.

availability/classes/info.php

@@ -311,17 +311,25 @@ abstract class info {
      * @param int $courseid Target course id
      * @param \base_logger $logger Logger for any warnings
      * @param int $dateoffset Date offset to be added to any dates (0 = none)
+     * @param \base_task $task Restore task
      */
-    public function update_after_restore($restoreid, $courseid, \base_logger $logger, $dateoffset) {
+    public function update_after_restore($restoreid, $courseid, \base_logger $logger,
+            $dateoffset, \base_task $task) {
         $tree = $this->get_availability_tree();
         // Set static data for use by get_restore_date_offset function.
-        self::$restoreinfo = array('restoreid' => $restoreid, 'dateoffset' => $dateoffset);
+        self::$restoreinfo = array('restoreid' => $restoreid, 'dateoffset' => $dateoffset,
+                'task' => $task);
         $changed = $tree->update_after_restore($restoreid, $courseid, $logger,
                 $this->get_thing_name());
         if ($changed) {
             // Save modified data.
-            $structure = $tree->save();
-            $this->set_in_database(json_encode($structure));
+            if ($tree->is_empty()) {
+                // If the tree is empty, but the tree has changed, remove this condition.
+                $this->set_in_database(null);
+            } else {
+                $structure = $tree->save();
+                $this->set_in_database(json_encode($structure));
+            }
         }
     }
 
@@ -343,6 +351,24 @@ abstract class info {
         return self::$restoreinfo['dateoffset'];
     }
 
+    /**
+     * Gets the restore task (specifically, the task that calls the
+     * update_after_restore method) for the current restore.
+     *
+     * @param string $restoreid Restore identifier
+     * @return \base_task Restore task
+     * @throws coding_exception If not in a restore (or not in that restore)
+     */
+    public static function get_restore_task($restoreid) {
+        if (!self::$restoreinfo) {
+            throw new coding_exception('Only valid during restore');
+        }
+        if (self::$restoreinfo['restoreid'] !== $restoreid) {
+            throw new coding_exception('Data not available for that restore id');
+        }
+        return self::$restoreinfo['task'];
+    }
+
     /**
      * Obtains the name of the item (cm_info or section_info, at present) that
      * this is controlling availability of. Name should be formatted ready

availability/classes/tree.php

@@ -663,10 +663,18 @@ class tree extends tree_node {
     public function update_after_restore($restoreid, $courseid,
             \base_logger $logger, $name) {
         $changed = false;
-        foreach ($this->children as $child) {
-            $thischanged = $child->update_after_restore($restoreid, $courseid,
-                    $logger, $name);
-            $changed = $changed || $thischanged;
+        foreach ($this->children as $index => $child) {
+            if ($child->include_after_restore($restoreid, $courseid, $logger, $name,
+                    info::get_restore_task($restoreid))) {
+                $thischanged = $child->update_after_restore($restoreid, $courseid,
+                        $logger, $name);
+                $changed = $changed || $thischanged;
+            } else {
+                unset($this->children[$index]);
+                unset($this->showchildren[$index]);
+                $this->showchildren = array_values($this->showchildren);
+                $changed = true;
+            }
         }
         return $changed;
     }

availability/classes/tree_node.php

@@ -82,13 +82,34 @@ abstract class tree_node {
      */
     public abstract function save();
 
+    /**
+     * Checks whether this node should be included after restore or not. The
+     * node may be removed depending on restore settings, which you can get from
+     * the $task object.
+     *
+     * By default nodes are still included after restore.
+     *
+     * @param string $restoreid Restore ID
+     * @param int $courseid ID of target course
+     * @param \base_logger $logger Logger for any warnings
+     * @param string $name Name of this item (for use in warning messages)
+     * @param \base_task $task Current restore task
+     * @return bool True if there was any change
+     */
+    public function include_after_restore($restoreid, $courseid, \base_logger $logger, $name,
+            \base_task $task) {
+        return true;
+    }
+
     /**
      * Updates this node after restore, returning true if anything changed.
      * The default behaviour is simply to return false. If there is a problem
      * with the update, $logger can be used to output a warning.
      *
      * Note: If you need information about the date offset, call
-     * \core_availability\info::get_restore_date_offset($restoreid).
+     * \core_availability\info::get_restore_date_offset($restoreid). For
+     * information on the restoring task and its settings, call
+     * \core_availability\info::get_restore_task($restoreid).
      *
      * @param string $restoreid Restore ID
      * @param int $courseid ID of target course