From b6715a7dda8086b3d0a0ef907a455511dbd94c85 Mon Sep 17 00:00:00 2001
From: Sara Arjona <sara@moodle.com>
Date: Tue, 22 Aug 2023 12:28:34 +0200
Subject: [PATCH] MDL-79102 forms: Add uniqueid var to avoid duplicated ids

A new static variable, $uniqueid, has been introduced to the
moodleform class. This enhancement allows for the simultaneous
presence of multiple forms with distinct IDs for action buttons
on a single page, thereby mitigating the accessibility concern
associated with duplicated IDs.
---
 .../bulk_activity_completion_renderer.php     | 16 +++++---
 course/defaultcompletion.php                  |  5 ++-
 lib/formslib.php                              | 37 ++++++++++++++-----
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/course/classes/output/bulk_activity_completion_renderer.php b/course/classes/output/bulk_activity_completion_renderer.php
index f923baa333f..1b9de5b0fe3 100644
--- a/course/classes/output/bulk_activity_completion_renderer.php
+++ b/course/classes/output/bulk_activity_completion_renderer.php
@@ -83,13 +83,17 @@ class core_course_bulk_activity_completion_renderer extends plugin_renderer_base
                 // Only create the form if it's different from the one that has been sent.
                 $modform = $form;
                 if (empty($form) || !in_array($module->id, array_keys($modules))) {
-                    $modform = new \core_completion_defaultedit_form(null, [
-                        'course' => $course,
-                        'modules' => [
-                            $module->id => $module,
+                    $modform = new \core_completion_defaultedit_form(
+                        null,
+                        [
+                            'course' => $course,
+                            'modules' => [
+                                $module->id => $module,
+                            ],
+                            'displaycancel' => false,
+                            'forceuniqueid' => true,
                         ],
-                        'displaycancel' => false,
-                    ]);
+                    );
                     $module->modulecollapsed = true;
                 }
                 $module->formhtml = $modform->render();
diff --git a/course/defaultcompletion.php b/course/defaultcompletion.php
index cc443214a40..88e68370466 100644
--- a/course/defaultcompletion.php
+++ b/course/defaultcompletion.php
@@ -69,7 +69,10 @@ foreach ($allmodules->modules as $module) {
 
 $form = null;
 if (!empty($modules)) {
-    $form = new core_completion_defaultedit_form(null, ['course' => $course, 'modules' => $modules, 'displaycancel' => false]);
+    $form = new core_completion_defaultedit_form(
+        null,
+        ['course' => $course, 'modules' => $modules, 'displaycancel' => false, 'forceuniqueid' => true]
+    );
     if (!$form->is_cancelled() && $data = $form->get_data()) {
         $data->modules = $modules;
         $manager->apply_default_completion($data, $form->has_custom_completion_rules(), $form->get_suffix());
diff --git a/lib/formslib.php b/lib/formslib.php
index 2eb2f78bd0d..30abf663dad 100644
--- a/lib/formslib.php
+++ b/lib/formslib.php
@@ -146,6 +146,9 @@ abstract class moodleform {
     /** @var bool|null stores the validation result of this form or null if not yet validated */
     protected $_validated = null;
 
+    /** @var int Unique identifier to be used for action buttons. */
+    static protected $uniqueid = 0;
+
     /**
      * The constructor function calls the abstract function definition() and it will then
      * process and clean and attempt to validate incoming data.
@@ -1359,22 +1362,36 @@ abstract class moodleform {
      * @param string $submitlabel label for submit button, defaults to get_string('savechanges')
      */
     public function add_action_buttons($cancel = true, $submitlabel = null) {
-        if (is_null($submitlabel)){
+        if (is_null($submitlabel)) {
             $submitlabel = get_string('savechanges');
         }
-        $mform =& $this->_form;
-        if ($cancel){
-            //when two elements we need a group
-            $buttonarray=array();
-            $buttonarray[] = &$mform->createElement('submit', 'submitbutton', $submitlabel);
-            $buttonarray[] = &$mform->createElement('cancel');
-            $mform->addGroup($buttonarray, 'buttonar', '', array(' '), false);
+        $mform = $this->_form;
+        // Only use uniqueid if the form defines it needs to be used.
+        $forceuniqueid = false;
+        if (is_array($this->_customdata)) {
+            $forceuniqueid = $this->_customdata['forceuniqueid'] ?? false;
+        }
+        // Keep the first action button as submitbutton (without uniqueid) because single forms pages expect this to happen.
+        $submitbuttonname = $forceuniqueid && $this::$uniqueid > 0 ? 'submitbutton_' . $this::$uniqueid : 'submitbutton';
+        if ($cancel) {
+            // When two elements we need a group.
+            $buttonarray = [
+                $mform->createElement('submit', $submitbuttonname, $submitlabel),
+                $mform->createElement('cancel'),
+            ];
+            $buttonarname = $forceuniqueid && $this::$uniqueid > 0 ? 'buttonar_' . $this::$uniqueid : 'buttonar';
+            $mform->addGroup($buttonarray, $buttonarname, '', [' '], false);
             $mform->closeHeaderBefore('buttonar');
         } else {
-            //no group needed
-            $mform->addElement('submit', 'submitbutton', $submitlabel);
+            // No group needed.
+            $mform->addElement('submit', $submitbuttonname, $submitlabel);
             $mform->closeHeaderBefore('submitbutton');
         }
+
+        // Increase the uniqueid so that we can have multiple forms with different ids for the action buttons on the same page.
+        if ($forceuniqueid) {
+            $this::$uniqueid++;
+        }
     }
 
     /**