MDL-43594 mod_assign: Fix calendar update on course reset

This patch fixes the updating of calendar events when the course
is reset and its start date is changed.

mod/assign/lib.php

@@ -87,6 +87,55 @@ function assign_reset_userdata($data) {
     return $status;
 }
 
+/**
+ * This standard function will check all instances of this module
+ * and make sure there are up-to-date events created for each of them.
+ * If courseid = 0, then every assignment event in the site is checked, else
+ * only assignment events belonging to the course specified are checked.
+ *
+ * @param int $courseid
+ * @return bool
+ */
+function assign_refresh_events($courseid = 0) {
+    global $CFG, $DB;
+    require_once($CFG->dirroot . '/mod/assign/locallib.php');
+
+    if ($courseid) {
+        // Make sure that the course id is numeric.
+        if (!is_numeric($courseid)) {
+            return false;
+        }
+        if (!$assigns = $DB->get_records('assign', array('course' => $courseid))) {
+            return false;
+        }
+        // Get course from courseid parameter.
+        if (!$course = $DB->get_record('course', array('id' => $courseid), '*')) {
+            return false;
+        }
+    } else {
+        if (!$assigns = $DB->get_records('assign')) {
+            return false;
+        }
+    }
+    foreach ($assigns as $assign) {
+        // Use assignment's course column if courseid parameter is not given.
+        if (!$courseid) {
+            $courseid = $assign->course;
+            if (!$course = $DB->get_record('course', array('id' => $courseid), '*')) {
+                continue;
+            }
+        }
+        if (!$cm = get_coursemodule_from_instance('assign', $assign->id, $courseid, false)) {
+            continue;
+        }
+        $context = context_module::instance($cm->id);
+        $assignment = new assign($context, $cm, $course);
+        $assignment->update_calendar($cm->id);
+    }
+
+    return true;
+}
+
 /**
  * Removes all grades from gradebook
  *

mod/assign/tests/lib_test.php

@@ -327,4 +327,43 @@ public function test_assign_get_completion_state() {
         $this->assertTrue($result);
     }
 
+    /**
+     * Tests for mod_assign_refresh_events.
+     */
+    public function test_assign_refresh_events() {
+        global $DB;
+        $duedate = time();
+        $this->setAdminUser();
+
+        $assign = $this->create_instance(array('duedate' => $duedate));
+
+        // Normal case, with existing course.
+        $this->assertTrue(assign_refresh_events($this->course->id));
+
+        $instance = $assign->get_instance();
+        $eventparams = array('modulename' => 'assign', 'instance' => $instance->id);
+        $event = $DB->get_record('event', $eventparams, '*', MUST_EXIST);
+        $this->assertEquals($event->timestart, $duedate);
+
+        // In case the course ID is passed as a numeric string.
+        $this->assertTrue(assign_refresh_events('' . $this->course->id));
+
+        // Course ID not provided.
+        $this->assertTrue(assign_refresh_events());
+
+        $eventparams = array('modulename' => 'assign');
+        $events = $DB->get_records('event', $eventparams);
+        foreach ($events as $event) {
+            if ($event->modulename === 'assign' && $event->instance === $instance->id) {
+                $this->assertEquals($event->timestart, $duedate);
+            }
+        }
+
+        // Non-existing course ID.
+        $this->assertFalse(assign_refresh_events(-1));
+
+        // Invalid course ID.
+        $this->assertFalse(assign_refresh_events('aaa'));
+    }
+
 }