MDL-87671 course: Add restricted page for sections

public/availability/tests/behat/display_availability.feature

@@ -181,3 +181,30 @@ Feature: Display availability for activities and sections
     And I press "Add restriction..."
     And I click on "Grade" "button" in the "Add restriction..." "dialogue"
     And the "alt" attribute of ".availability-item .availability-eye img" "css_element" should contain "Item name displayed"
+
+  Scenario: Restricted section page
+    # Set up.
+    Given the following config values are set as admin:
+      | unaddableblocks | | theme_boost|
+    And the following "groups" exist:
+      | course | name | idnumber |
+      | C1     | G1   | GI1      |
+    And the following "groupings" exist:
+      | name | course | idnumber |
+      | GX1  | C1     | GXI1     |
+    And I am on the "C1" "Course" page logged in as "teacher1"
+    And I turn editing mode on
+    And I add the "Navigation" block if not present
+    # Add a restriction to section 1 (visible to students).
+    And I edit the section "1"
+    And I set the following fields to these values:
+      | Access restrictions | Grouping: GX1 |
+    And I press "Save changes"
+    # Change to student view.
+    And I am on the "Course 1" "Course" page logged in as "student1"
+    And "Section 1" "link" should appear before "Section 2" "link" in the "Navigation" "block"
+    When I click on "Section 1" "link" in the "Navigation" "block"
+    # Section 1 should be visible and show info.
+    And I should see "Section 1" in the "page-header" "region"
+    And I should see "Not available unless" in the "region-main" "region"
+    And "Page 1" "link" should not exist in the "region-main" "region"

public/course/classes/route/controller/restricted_section.php

@@ -0,0 +1,87 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_course\route\controller;
+
+use core\router\route;
+use core\router\require_login;
+use core_course\modinfo;
+use core_course\section_info;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+
+/**
+ * Restricted section redirection.
+ *
+ * @package    core_course
+ * @copyright  2026 Amaia Anabitarte <[email protected]>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class restricted_section {
+    use \core\router\route_controller;
+
+    /**
+     * Restricted section.
+     *
+     * @param ResponseInterface $response
+     * @param section_info $sectioninfo
+     * @return ResponseInterface
+     */
+    #[route(
+        path: '/sections/{section}/restricted',
+        pathtypes: [
+            new \core\router\parameters\path_section(),
+        ],
+        requirelogin: new require_login(
+            requirelogin: true,
+            courseattributename: 'course',
+        ),
+    )]
+    public function restricted_section_page(
+        ServerRequestInterface $request,
+        ResponseInterface $response,
+        \stdClass $section,
+    ): ResponseInterface {
+        global $OUTPUT, $PAGE, $CFG;
+
+        require_once($CFG->dirroot . '/course/lib.php');
+
+        $course = get_course($section->course);
+        $format = course_get_format($course->id);
+        $format->set_sectionid($section->id);
+        $outputclass = $format->get_output_classname('content');
+        $sectionoutput = new $outputclass($format);
+        $PAGE->set_url('/course/section.php', ['id' => $section->id]);
+        $PAGE->set_course($course);
+
+        $PAGE->set_pagelayout('course');
+        $PAGE->add_body_classes(['limitedwidth', 'single-section-page']);
+        $PAGE->set_pagetype('course-view-section-' . $course->format . '-restricted');
+        $PAGE->set_context(\context_course::instance($course->id));
+
+        $sectiontitle = $format->get_section_name($section);
+        $strtitle = get_string('restrictedtitle', 'course', $sectiontitle);
+        $PAGE->set_title($strtitle . \moodle_page::TITLE_SEPARATOR . $course->shortname);
+        $PAGE->set_heading($sectiontitle);
+        $PAGE->set_secondary_navigation(false);
+        $renderer = $format->get_renderer($PAGE);
+        $response->getBody()->write($OUTPUT->header());
+        $response->getBody()->write($renderer->render($sectionoutput));
+        $response->getBody()->write($OUTPUT->footer());
+
+        return $response;
+    }
+}

public/course/section.php

@@ -96,9 +96,11 @@ if (!$sectioninfo->uservisible) {
     // Check if coursesection has conditions affecting availability and if
     // so, output availability info.
     if ($sectioninfo->visible && $sectioninfo->availableinfo) {
-        $sectionname = get_section_name($course, $sectioninfo);
-        $message = get_string('notavailablecourse', '', $sectionname);
-        redirect(course_get_url($course), $message, null, \core\output\notification::NOTIFY_ERROR);
+        $url = \core\router\util::get_path_for_callable(
+            [\core_course\route\controller\restricted_section::class, 'restricted_section_page'],
+            ['section' => $sectioninfo->id],
+        );
+        redirect($url, '', null);
     } else {
         // Note: We actually already know they don't have this capability
         // or uservisible would have been true; this is just to get the