MDL-66694 mod_forum: Word & char count update consistency fixes

Charcount logic is now consistent with wordcount in the post exporter.
Counts update now called in forum_udpate_instance since it is updating
the data.

mod/forum/classes/local/entities/post.php

@@ -348,7 +348,7 @@ public function get_charcount() : ?int {
      * @param \stdClass $record A record ready to be inserted / updated in DB.
      * @return \stdClass The same record with 'wordcount' and 'charcount' attributes.
      */
-    public static function add_message_counts(\stdClass $record): \stdClass {
+    public static function add_message_counts(\stdClass $record) : \stdClass {
         if (!empty($record->message)) {
             $record->wordcount = count_words($record->message);
             $record->charcount = count_letters($record->message);

mod/forum/classes/local/exporters/post.php

@@ -419,6 +419,10 @@ protected function get_other_values(renderer_base $output) {
         $showwordcount = $forum->should_display_word_count();
         if ($showwordcount) {
             $wordcount = $post->get_wordcount() ?? count_words($message);
+            $charcount = $post->get_charcount() ?? count_letters($message);
+        } else {
+            $wordcount = null;
+            $charcount = null;
         }
 
         return [
@@ -436,8 +440,8 @@ protected function get_other_values(renderer_base $output) {
             'isdeleted' => $isdeleted,
             'isprivatereply' => $isprivatereply,
             'haswordcount' => $showwordcount,
-            'wordcount' => $showwordcount ? $wordcount : null,
-            'charcount' => $post->get_charcount(),
+            'wordcount' => $wordcount,
+            'charcount' => $charcount,
             'capabilities' => [
                 'view' => $canview,
                 'edit' => $canedit,

mod/forum/lib.php

@@ -240,6 +240,7 @@ function forum_update_instance($forum, $mform) {
             $post->message = file_save_draft_area_files($draftid, $modcontext->id, 'mod_forum', 'post', $post->id, $options, $post->message);
         }
 
+        \mod_forum\local\entities\post::add_message_counts($post);
         $DB->update_record('forum_posts', $post);
         $discussion->name = $forum->name;
         $DB->update_record('forum_discussions', $discussion);