Handle adding page title to content

Just ran into this. Error in log:

LogicException: The page_title_block block plugin does not support previews. in Drupal\experience_builder\Plugin\ExperienceBuilder\ComponentSource\BlockComponent->renderComponent() (line 145 of /var/www/html/web/modules/contrib/experience_builder/src/Plugin/ExperienceBuilder/ComponentSource/BlockComponent.php).

Related: the generalized variant of this problem/symptom: 📌 Improve server-side error handling Active .

Fixing: not possible until much later, and why

fixing the block

This is not possible until maybe 📌 [later phase] ApiPreviewController must use the previewed route's controller, and override canonical content entity routes' received entity object Postponed , because this is one of the two highly special blocks in Drupal: they're fed information resulting from the execution of the route's controller!

Hence the error message, which originates from:

// Allow global context to be injected by suspending the fiber.
// @see \Drupal\experience_builder\Plugin\DisplayVariant\PageTemplateDisplayVariant::build()
if ($block instanceof MainContentBlockPluginInterface || $block instanceof TitleBlockPluginInterface) {
if (\Fiber::getCurrent() === NULL) {
throw new \LogicException(sprintf('The %s block plugin does not support previews.', $block->getPluginId()));
}
\Fiber::suspend($block);
}

Note that the "main content" block has the same problem, and triggers the same exact error message (I just manually tested to verify). Issue title updated. 👍

And even then (after #3491701) this would be tricky to get right: if you're modifying the title of a node, then we'd have to:

• get XB UI-submitted data to be transformed into an ephemeral content entity object
• automatically get the canonical entity route's _title callback executed:
• IOW: pass the ephemeral entity to \Drupal\Core\Entity\Controller\EntityController::title()
• pass the return value of that into \Drupal\experience_builder\Plugin\DisplayVariant\PageTemplateDisplayVariant
• … which in turn would allow the code above to be modified to call \Drupal\Core\Block\TitleBlockPluginInterface::setTitle()

🤯, right?!

But we'll have to do almost exactly that. We can't change all innards of Drupal.

Work-around: fallback

Unless you are fine with adding fallback rendering! 😄

We could make ApiPreviewController leap ahead of #3491701 slightly and make it assume that it's always used on a content entity route (which is indeed true in XB's UI today):

1. use $label_field_name = $entity->getEntityType()->getkey('label') to get the name of the label field
2. use $body['entity_form_fields'][$label_field_name . '[0][value]'] to get the current entity title
3. wrap the ->toRenderable() call in fiber execution similar to \Drupal\experience_builder\Plugin\DisplayVariant\PageTemplateDisplayVariant::build()

Tada, it works!

Alternative: disallowing

disallowing adding the block there

This is maybe possible. Depends on what you mean by "there".

You talked before about how the "main content" block should always be placed in the content region. Can we do the same for the "page title" block? Even though some themes may want to place it somewhere else?

Olivero puts it in the content_above region by default, so this seems like a bad idea?

I think the solution for "Page title block" and "Main page content block" are different.

The "Main page content block" we should just hide from the XB library completely. I already opened an issue for this 🐛 Hide main page content block from XB Active .

The "Page title block" we should not hard code to a region because it's not uncommon for a theme to not want to display the page title at all. I assume that it would be more common for people set this in the content type template rather than in the page template. There are some edge cases where this doesn't work but in most cases people wouldn't want to show a title at least on the XB pages.

The proposed fallback seems like a good approach for now. The assumption that XB is always used on a content entity route is acceptable for now but this may change in future, e.g., to allow entering XB using a view page URL.

👍

P.S.: d'oh, right, I finished writing this while on a meeting — but yes, I intend for 📌 Consider refactoring page_template into page_region(s) Active to hardcode what the content PageRegion config entity contains: the main block, and nothing else!

The 'Drupal\Core\Block\TitleBlockPluginInterface' component interface must be present.

It looks like we also have an exception in place for the scenario where a title isn't placed. We should get rid of that since we should accept the fact that some sites may not want to place the title block in the page template.

@lauriii opened 📌 Page title should not be required Active for #10, and I fixed it.

I think the work-around I articulated 15 days → ago at might've become simpler thanks to 🐛 Changing page title doesn't update in the review changes panel Active .

What I proposed appears to work. This still needs refining though:

diff --git a/src/Controller/ApiLayoutController.php b/src/Controller/ApiLayoutController.php
index e8804d48..287a39bc 100644
--- a/src/Controller/ApiLayoutController.php
+++ b/src/Controller/ApiLayoutController.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Drupal\experience_builder\Controller;
 
 use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\Block\TitleBlockPluginInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityPublishedInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
@@ -37,6 +38,8 @@ final class ApiLayoutController {
   private array $regions;
   private array $regionsClientSideIds;
 
+  private $t;
+
   public function __construct(
     private readonly AutoSaveManager $autoSaveManager,
     private readonly ThemeManagerInterface $themeManager,
@@ -353,10 +356,25 @@ final class ApiLayoutController {
       'model' => $model,
       'entity_form_fields' => $body['entity_form_fields'],
     ], $entity, validate: FALSE);
+    // @todo improve
+    $entity_title = $body['entity_form_fields']['title[0][value]'];
     $field_name = InternalXbFieldNameResolver::getXbFieldName($entity);
     $item = $entity->get($field_name)->first();
     assert($item instanceof ComponentTreeItem);
-    $renderable = $item->toRenderable();
+    $fiber = new \Fiber(fn() => $item->toRenderable());
+    $component_instance = $fiber->start();
+    // @see \Drupal\experience_builder\Plugin\DisplayVariant\XbPageVariant::build()
+    while ($fiber->isSuspended()) {
+      $component_instance = match (TRUE) {
+        $component_instance instanceof TitleBlockPluginInterface => (function () use ($component_instance, $fiber, $entity_title) {
+          $component_instance->setTitle($entity_title);
+          return $fiber->resume();
+        })(),
+        default => new \LogicException(),
+      };
+    }
+    assert($fiber->isTerminated());
+    $renderable = $fiber->getReturn();
 
     if (isset($renderable[ComponentTreeStructure::ROOT_UUID])) {
       $build = $renderable[ComponentTreeStructure::ROOT_UUID];

f.mazeikis → made their first commit to this issue’s fork.

Test coverage in \Drupal\Tests\experience_builder\Kernel\ApiLayoutControllerPostTest seems like the most feasible approach.