MDL-25660 recreate all workshop calendar events

Due to complex workshop upgrade path from 1.9 and missing calendar events
support in 2.x, the only safe way to get rid of potentially invalid
calendar events (such as those reported in MDL-26687) is to remove all
current workshop events and recreate them from scratch.

mod/workshop/db/upgrade.php

@@ -322,5 +322,42 @@ function xmldb_workshop_upgrade($oldversion) {
     // Moodle v2.2.0 release upgrade line
     // Put any upgrade step following this
 
+    /**
+     * Remove all workshop calendar events
+     */
+    if ($oldversion < 2011112901) {
+        require_once($CFG->dirroot . '/calendar/lib.php');
+        $events = $DB->get_records('event', array('modulename' => 'workshop'));
+        foreach ($events as $event) {
+            $event = calendar_event::load($event);
+            $event->delete();
+        }
+        upgrade_mod_savepoint(true, 2011112901, 'workshop');
+    }
+
+    /**
+     * Recreate all workshop calendar events
+     */
+    if ($oldversion < 2011112902) {
+        require_once(dirname(dirname(__FILE__)) . '/lib.php');
+
+        $sql = "SELECT w.id, w.course, w.name, w.intro, w.introformat, w.submissionstart,
+                       w.submissionend, w.assessmentstart, w.assessmentend,
+                       cm.id AS cmid
+                  FROM {workshop} w
+                  JOIN {modules} m ON m.name = 'workshop'
+                  JOIN {course_modules} cm ON (cm.module = m.id AND cm.course = w.course AND cm.instance = w.id)";
+
+        $rs = $DB->get_recordset_sql($sql);
+
+        foreach ($rs as $workshop) {
+            $cmid = $workshop->cmid;
+            unset($workshop->cmid);
+            workshop_calendar_update($workshop, $cmid);
+        }
+        $rs->close();
+        upgrade_mod_savepoint(true, 2011112902, 'workshop');
+    }
+
     return true;
 }

mod/workshop/version.php

@@ -25,7 +25,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$module->version   = 2011112900;       // The current module version (Date: YYYYMMDDXX)
+$module->version   = 2011112902;       // The current module version (Date: YYYYMMDDXX)
 $module->requires  = 2011112900;       // Requires this Moodle version
 $module->component = 'mod_workshop';   // Full name of the plugin (used for diagnostics)
 $module->cron      = 0;