General developer forum

Thanks Richard for the alternative solution.

I've finally figured it out and here is a proof of concept. Attached are the files I've modified in a Moodle $version  = 2017111302.04;  $release  = '3.4.2+ (Build: 20180405)';.

Warning for non-devs: This is a proof of concept that hack the core code! Don't try this in your production server.

Here is the course maintenance mode settings.

And the output when an enrolled student tries to enter a course in maintenance mode.

The following changes should be applied on a fresh install because I could not resolve an exception when I added the XMLDB generated php code in /lib/db/upgrade.php. So the db change is in /lib/db/install.xml .

lang/en/role.php

$string['course:coursemaintenanceaccess'] = 'Access course site while in maintenance mode';

lang/en/moodle.php

$string['coursemaintenance'] = 'Course maintenance mode';
$string['coursemaintenance_message'] = 'Course maintenance message';
$string['coursemaintenance_help'] = 'Sets the course in maintenance mode.';
$string['coursemaintenance_message_help'] = 'Allows custom message in maintenance mode.';

admin/settings/courses.php
line 65

    //Course maintenance mode
    $temp->add(new admin_setting_configselect('moodlecourse/coursemaintenance', new lang_string('coursemaintenance'), new lang_string('coursemaintenance_help'), 0,array(0 => new lang_string('no'), 1 => new lang_string('yes'))));


course/edit_form.PHP
line 124
        //Course maintenance mode
        $mform->addElement('selectyesno', 'coursemaintenance', get_string('coursemaintenance'));
        $mform->addHelpButton('coursemaintenance', 'coursemaintenance');
        $mform->setDefault('coursemaintenance', $courseconfig->coursemaintenance);
       
        //Course maintenance message
        $mform->addElement('textarea','coursemaintenance_message', get_string('coursemaintenance_message'));
        $mform->addHelpButton('coursemaintenance_message', 'coursemaintenance_message');
        $mform->setType('shortname', PARAM_TEXT);

lib/db/access.php
line 2381
    'moodle/course:coursemaintenanceaccess' => array(
        'captype' => 'write',
        'contextlevel' => CONTEXT_COURSE,
        'archetypes' => array(
            'teacher' => CAP_ALLOW,
            'editingteacher' => CAP_ALLOW,
            'manager' => CAP_ALLOW
        )
    ),

lib/db/services.php
line 451
    'core_course_update_courses' => array(
        'classname' => 'core_course_external',
        'methodname' => 'update_courses',
        'classpath' => 'course/externallib.php',
        'description' => 'Update courses',
        'type' => 'write',
        'capabilities' => 'moodle/course:update, moodle/course:changecategory, moodle/course:changefullname, '
        . 'moodle/course:changeshortname, moodle/course:changeidnumber, moodle/course:changesummary, moodle/course:visibility, moodle/course:coursemaintenanceaccess'
    ),


moodle/lib/db/install.xml
line 91
        <FIELD NAME="visible" TYPE="int" LENGTH="1" NOTNULL="true" DEFAULT="1" SEQUENCE="false"/>
        <FIELD NAME="visibleold" TYPE="int" LENGTH="1" NOTNULL="true" DEFAULT="1" SEQUENCE="false" COMMENT="the state of visible field when hiding parent category, this helps us to recover hidden states when unhiding the parent category later"/>

        <FIELD NAME="coursemaintenance" TYPE="int" LENGTH="4" NOTNULL="true" DEFAULT="0" SEQUENCE="false"/>
        <FIELD NAME="coursemaintenance_message" TYPE="text" NOTNULL="false" SEQUENCE="false"/>

/lib/moodlelib.php
line 2876

        //course maintenance test
        //$coursemaintenance = true;
       
        if (!has_capability("moodle/course:coursemaintenanceaccess",$coursecontext) and $access and ($course->coursemaintenance == 1)) {
            if ($preventredirect) {
                throw new require_login_exception('The course is not available yet.');
            }
            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            $PAGE->set_context(null);
            print_coursemaintenance_message($course->coursemaintenance_message,$course->fullname);
        }

/lib/weblib.php
line 3004

/**
 * Prints a maintenance message for course.
 */
function print_coursemaintenance_message($message,$fullname) {
    global $CFG, $SITE, $PAGE, $OUTPUT;
   
    header($_SERVER['SERVER_PROTOCOL'] . ' 503 Moodle under maintenance');
    header('Status: 503 Moodle under maintenance');
    header('Retry-After: 300');
   
    $PAGE->set_pagetype('maintenance-message');
    $PAGE->set_pagelayout('columns1');
    $PAGE->set_title(strip_tags($SITE->fullname));
    $PAGE->set_heading($fullname);
    echo $OUTPUT->header();
    echo $OUTPUT->heading("Course Maintenance");
        echo $OUTPUT->box_start('coursemaintenance_message generalbox boxwidthwide boxaligncenter');
          echo $message;
        echo $OUTPUT->box_end();
    echo $OUTPUT->footer();
    die;
}