\Drupal\Core\EventSubscriber\ViewSubscriber::onHtml() does not allow controllers to return string content

Can we have some fix test?

This is all being changed entirely by #2068471: Normalize Controller/View-listener behavior with a Page object anyway, and is going to conflict with that (as does everything, it seems). Since it's not failing any tests now, should we just let that issue fix it?

This is all being changed entirely by #2068471: Normalize Controller/View-listener behavior with a Page object anyway, and is going to conflict with that (as does everything, it seems). Since it's not failing any tests now, should we just let that issue fix it?

That patch will just exist for ever, so we ensure that there is constant effort with rerolls.

But yeah this is throwing a notice on every views screen.

Yeah, agreed with getting this in to fix the bug for now. But one small point...

+++ b/core/lib/Drupal/Core/EventSubscriber/ViewSubscriber.php
@@ -175,6 +175,11 @@ public function onHtml(GetResponseForControllerResultEvent $event) {
     // If no title was returned fall back to one defined in the route.
+    if (!is_array($page_callback_result)) {
+      $page_callback_result = array(
+        '#markup' => $page_callback_result,
+      );
+    }
     if (!isset($page_callback_result['#title'])) {

This comment is no longer accurate for what the code is doing. Should be moved below. I'd just do that myself, except I don't understand exactly what this is testing for. Is it something like:

// Some page callbacks might return strings rather than arrays. If so, convert it to a render array?

Let's get it in, for real.

This is a blocker for 5.4

Committed 021452d and pushed to 8.x. Thanks!