MDL-66903 core: Introduce \core_component::reset to replace hacks

Traditionally we have done this using reflection and it would be better
to do this in a 'proper' fashion in case we ever need to change how it
works.

lib/classes/component.php

@@ -274,7 +274,6 @@ class core_component {
         return $file;
     }
 
-
     /**
      * Initialise caches, always call before accessing self:: caches.
      */
@@ -399,6 +398,17 @@ class core_component {
         }
     }
 
+    /**
+     * Reset the initialisation of the component utility.
+     *
+     * Note: It should not be necessary to call this in regular code.
+     * Please only use it where strictly required.
+     */
+    public static function reset(): void {
+        // The autoloader will re-initialise if plugintypes is null.
+        self::$plugintypes = null;
+    }
+
     /**
      * Are we in developer debug mode?
      *

lib/phpunit/classes/advanced_testcase.php

@@ -79,8 +79,9 @@ abstract class advanced_testcase extends base_testcase {
             // Reset global state after test and test failure.
             $CFG = phpunit_util::get_global_backup('CFG');
             $DB = phpunit_util::get_global_backup('DB');
-            // This is _hacky_. We need to reset the autoloader, and this is the only way to do so right now.
-            (new ReflectionProperty(\core_component::class, 'plugintypes'))->setValue(null, null);
+
+            // We need to reset the autoloader.
+            \core_component::reset();
         }
 
         if (isset($e)) {

lib/tests/component_test.php

@@ -38,8 +38,7 @@ final class component_test extends advanced_testcase {
     public function tearDown(): void {
         parent::tearDown();
 
-        $plugintypes = new ReflectionProperty(\core_component::class, 'plugintypes');
-        $plugintypes->setValue(null, null);
+        \core_component::reset();
     }
 
     public function test_get_core_subsystems(): void {
@@ -959,7 +958,7 @@ final class component_test extends advanced_testcase {
         // We have to override the dirroot and libdir, and then reset the plugintypes property.
         $CFG->dirroot = $vfileroot->url();
         $CFG->libdir = $vfileroot->url() . '/lib';
-        (new ReflectionProperty('core_component', 'plugintypes'))->setValue(null, null);
+        \core_component::reset();
 
         // Existing classes do not break.
         $this->assertTrue(