MDL-81503 core_course: Improve section not found error

course/section.php

@@ -32,7 +32,29 @@
 // This parameter is used by the classic theme to force editing on.
 $edit = optional_param('edit', -1, PARAM_BOOL);
 
-$section = $DB->get_record('course_sections', ['id' => $sectionid], '*', MUST_EXIST);
+if (!$section = $DB->get_record('course_sections', ['id' => $sectionid], '*')) {
+    $url = new moodle_url('/');
+    $PAGE->set_context(\core\context\system::instance());
+    $PAGE->set_url($url);
+    $PAGE->set_pagelayout('course');
+    $PAGE->add_body_classes(['limitedwidth', 'single-section-page']);
+    $PAGE->set_title(get_string('notfound', 'error'));
+    $PAGE->set_heading($SITE->fullname);
+    echo $OUTPUT->header();
+
+    $errortext = new \core\output\notification(
+            get_string('sectioncantbefound', 'error'),
+            \core\output\notification::NOTIFY_ERROR
+    );
+    echo $OUTPUT->render($errortext);
+
+    $button = new single_button($url, get_string('gobacktosite'), 'get', single_button::BUTTON_PRIMARY);
+    $button->class = 'continuebutton';
+    echo $OUTPUT->render($button);
+
+    echo $OUTPUT->footer();
+    die();
+}
 
 // Defined here to avoid notices on errors.
 $PAGE->set_url('/course/section.php', ['id' => $sectionid]);

lang/en/error.php

@@ -483,6 +483,7 @@
 $string['nostatstodisplay'] = 'Sorry, there is no available data to display';
 $string['notallowedtoupdateprefremotely'] = 'You are not allowed to update this user preference remotely';
 $string['notavailable'] = 'That is not currently available';
+$string['notfound'] = 'Not found';
 $string['notlocalisederrormessage'] = '{$a}';
 $string['notmemberofgroup'] = 'You are not a member of this course group';
 $string['notownerofkey'] = 'You are not owner of this key';
@@ -529,6 +530,7 @@
 $string['reverseproxyabused'] = 'Reverse proxy enabled so the server cannot be accessed directly.<br />Please contact the server administrator.';
 $string['rpcerror'] = 'Ooops! Your MNET communication has failed! Here\'s that error message to pass on to your administrator: {$a}';
 $string['secretalreadyused'] = 'Change password confirmation link was already used, password was not changed';
+$string['sectioncantbefound'] = '<p><b>This content can\'t be found</b></p><p>It may have been deleted, or the URL may be incorrect.</p>';
 $string['sectionnotexist'] = 'This section does not exist';
 $string['sendmessage'] = 'Send message';
 $string['sendmessagesent'] = 'Thanks for your feedback about:<br>{$a}';

lang/en/moodle.php

@@ -968,6 +968,7 @@
 $string['geolocation'] = 'latitude - longitude';
 $string['gettheselogs'] = 'Get these logs';
 $string['go'] = 'Go';
+$string['gobacktosite'] = 'Go back to site';
 $string['gpl'] = 'Copyright (C) 1999 onwards Martin Dougiamas (https://moodle.com)
 
 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.