MDL-70537 Availability: Avoid recursive calls to $cm->name

These recursive calls didn't work in PHP 7.3 and below, but in PHP
7.4 they also cause a fatal error which means if you have invalid
availability data, the whole page might die.

availability/classes/info.php

@@ -290,9 +290,9 @@ public function get_full_information(\course_modinfo $modinfo = null) {
      */
     protected function warn_about_invalid_availability(\coding_exception $e) {
         $name = $this->get_thing_name();
-        // If it occurs while building modinfo based on somebody calling $cm->name,
-        // we can't get $cm->name, and this line will cause a warning.
-        $htmlname = @$this->format_info($name, $this->course);
+        $htmlname = $this->format_info($name, $this->course);
+        // Because we call format_info here, likely in the middle of building dynamic data for the
+        // activity, there could be a chance that the name might not be available.
         if ($htmlname === '') {
             // So instead use the numbers (cmid) from the tag.
             $htmlname = preg_replace('~[^0-9]~', '', $name);
@@ -739,11 +739,11 @@ public static function format_info($inforenderable, $courseorid) {
         $info = preg_replace_callback('~<AVAILABILITY_CMNAME_([0-9]+)/>~',
                 function($matches) use($modinfo, $context) {
                     $cm = $modinfo->get_cm($matches[1]);
-                    if ($cm->has_view() and $cm->uservisible) {
+                    if ($cm->has_view() and $cm->get_user_visible()) {
                         // Help student by providing a link to the module which is preventing availability.
-                        return \html_writer::link($cm->url, format_string($cm->name, true, array('context' => $context)));
+                        return \html_writer::link($cm->get_url(), format_string($cm->get_name(), true, ['context' => $context]));
                     } else {
-                        return format_string($cm->name, true, array('context' => $context));
+                        return format_string($cm->get_name(), true, ['context' => $context]);
                     }
                 }, $info);
 

availability/tests/info_test.php

@@ -511,4 +511,33 @@ public function test_filter_user_list() {
         sort($result);
         $this->assertEquals($expected, $result);
     }
+
+    /**
+     * Tests the info_module class when involved in a recursive call to $cm->name.
+     */
+    public function test_info_recursive_name_call() {
+        global $DB;
+
+        $this->resetAfterTest();
+
+        // Create a course and page.
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course();
+        $page1 = $generator->create_module('page', ['course' => $course->id, 'name' => 'Page1']);
+
+        // Set invalid availability.
+        $DB->set_field('course_modules', 'availability', 'not valid', ['id' => $page1->cmid]);
+
+        // Get the cm_info object.
+        $this->setAdminUser();
+        $modinfo = get_fast_modinfo($course);
+        $cm1 = $modinfo->get_cm($page1->cmid);
+
+        // At this point we will generate dynamic data for $cm1, which will cause the debugging
+        // call below.
+        $this->assertEquals('Page1', $cm1->name);
+
+        $this->assertDebuggingCalled('Error processing availability data for ' .
+                '‘Page1’: Invalid availability text');
+    }
 }

lib/modinfolib.php

@@ -1312,9 +1312,15 @@ public function has_view() {
     }
 
     /**
+     * Gets the URL to link to for this module.
+     *
+     * This method is normally called by the property ->url, but can be called directly if
+     * there is a case when it might be called recursively (you can't call property values
+     * recursively).
+     *
      * @return moodle_url URL to link to for this module, or null if it doesn't have a view page
      */
-    private function get_url() {
+    public function get_url() {
         $this->obtain_dynamic_data();
         return $this->url;
     }
@@ -1360,9 +1366,13 @@ public function get_formatted_content($options = array()) {
 
     /**
      * Getter method for property $name, ensures that dynamic data is obtained.
+     *
+     * This method is normally called by the property ->name, but can be called directly if there
+     * is a case when it might be called recursively (you can't call property values recursively).
+     *
      * @return string
      */
-    private function get_name() {
+    public function get_name() {
         $this->obtain_dynamic_data();
         return $this->name;
     }
@@ -1915,9 +1925,14 @@ private function obtain_dynamic_data() {
 
     /**
      * Getter method for property $uservisible, ensures that dynamic data is retrieved.
+     *
+     * This method is normally called by the property ->uservisible, but can be called directly if
+     * there is a case when it might be called recursively (you can't call property values
+     * recursively).
+     *
      * @return bool
      */
-    private function get_user_visible() {
+    public function get_user_visible() {
         $this->obtain_dynamic_data();
         return $this->uservisible;
     }