MDL-79174 availability: Allow group condition to use hidden groups

Previously, groups with GROUP_VISIBILITY_NONE could be selected for an
availability condition, but as the group API did not return a user's own
groups with this visibility, the condition's is_available check always
failed.

This change uses the new $includehidden parameter to get all of a user's
groups from groups_get_user_groups when evaluating the condition, so
these groups work as expected. Due to the enforced hiding of conditions
containing these groups, they will never be seen by the user.

availability/classes/info.php

@@ -49,6 +49,9 @@ abstract class info {
     /** @var tree Availability configuration, decoded from JSON; null if unset */
     protected $availabilitytree;
 
+    /** @var array The groups the current user belongs to. */
+    protected $groups;
+
     /** @var array|null Array of information about current restore if any */
     protected static $restoreinfo = null;
 
@@ -65,6 +68,7 @@ abstract class info {
         $this->course = $course;
         $this->visible = (bool)$visible;
         $this->availability = $availability;
+        $this->groups = null;
     }
 
     /**
@@ -800,4 +804,28 @@ abstract class info {
         }
         return false;
     }
+
+    /**
+     * Returns groups that the current user belongs to on the course. Note: If not already
+     * available, this may make a database query.
+     *
+     * This will include groups the user is not allowed to see themselves, so check visibility
+     * before displaying groups to the user.
+     *
+     * @param int $groupingid Grouping ID or 0 (default) for all groups
+     * @return int[] Array of int (group id) => int (same group id again); empty array if none
+     */
+    public function get_groups(int $groupingid = 0): array {
+        global $USER;
+        if (is_null($this->groups)) {
+            $allgroups = groups_get_user_groups($this->course->id, $USER->id, true);
+            $this->groups = $allgroups;
+        } else {
+            $allgroups = $this->groups;
+        }
+        if (!isset($allgroups[$groupingid])) {
+            return [];
+        }
+        return $allgroups[$groupingid];
+    }
 }