MDL-64820 forum: add classes to first post to fix behat

mod/forum/classes/local/factories/renderer.php

@@ -194,6 +194,7 @@ class renderer {
                             unset($exportedpost->author);
                         }
 
+                        $exportedpost->firstpost = false;
                         $exportedpost->readonly = $readonly;
                         $exportedpost->hasreplies = false;
                         $exportedpost->replies = [];
@@ -228,6 +229,11 @@ class renderer {
                     $exportedposts = [$exportedfirstpost];
                 }
 
+                if (!empty($exportedposts)) {
+                    // Need to identify the first post so that we can use it in behat tests.
+                    $exportedposts[0]->firstpost = true;
+                }
+
                 return $exportedposts;
             }
         );

mod/forum/templates/forum_discussion_post.mustache

@@ -31,7 +31,11 @@
 }}
 <article id="p{{id}}" class="relativelink mb-2" tabindex="-1" data-post-id="{{id}}">
 
-    <div class="d-flex border p-2 mb-2 forumpost {{#unread}}unread{{/unread}}">
+    <!-- The firstpost and starter classes below aren't used for anything other than to identify the first post in behat -->
+    <div
+        class="d-flex border p-2 mb-2 forumpost {{#unread}}unread{{/unread}} {{#firstpost}}firstpost starter{{/firstpost}}"
+        aria-label='{{#str}} postbyuser, mod_forum, {"post": "{{subject}}", "user": "{{author.fullname}}"} {{/str}}'
+    >
         {{#isfirstunread}}<a id="unread"></a>{{/isfirstunread}}
         <div style="width: 45px;">
             {{^isdeleted}}