How to get the context node in a custom block inside a views list?

Question

I have a view which displays all pictures of the content type photo. I've set some fields in this view for the display.

This is how iIrender the list of pictures:

views-view-fields--photo.html

<figure class="element-item {{ fields['name'].content|lower }}">
    <a href="{{ fields['field_photo_1'].content|lower }}">
        <img src="{{ fields['field_photo'].content }}"/>
    </a>
    <figcaption>
        <div class="date">{{ fields['field_date'].content }}</div>
        <div class="lieu">{{ fields['field_lieu'].content }}</div>
    </figcaption>
</figure>
{{ drupal_block('comment_block') }}

I use the Twig tweak module to render a custom block in this template. This block should load all comments for the picture. For that, I need to pass the nid of the node to my block.

Here's the code of the block:

CommentBlock.php

/**
 * Provides a 'CommentBlock' block.
 *
 * @Block(
 *  id = "comment_block",
 *  admin_label = @Translation("Comment block"),
 *  context = {
 *    "node" = @ContextDefinition("entity:node", label = @Translation("Node"))
 *  }
 * )
 */
class CommentBlock extends BlockBase implements ContainerFactoryPluginInterface {

  /**
   * Drupal\Core\Entity\EntityTypeManagerInterface definition.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * Constructs a new CommentBlock object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param string $plugin_definition
   *   The plugin implementation definition.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->entityTypeManager = $entity_type_manager;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('entity_type.manager')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function build() {

    $build = [];

    $node = $this->getContextValue('node');
    kint($node->id());

    $build['#theme'] = 'comment_ajax';

    return $build;
  }

}

What I try is to get the context of the views row into my block. But I get this error:

Drupal\Component\Plugin\Exception\ContextException : Required contexts without a value: node

What am I doing wrong?

I can load my block from template_preprocess_views_view_fields() to link with the nid but I try to understand the context annotation.

---

Update

Here's a picture of the view, my custom block returns just a link name "Comment".

I now load the block programmatically instead of using drupal_block in the preprocess.

$block             = \Drupal\block\Entity\Block::load('commentblock');
$variables['test'] = \Drupal::entityTypeManager()
  ->getViewBuilder('block')
  ->view($block);

Then I print this block in views-view-fields.html.twig:

{{ fields['title'].content }}
{{ test }}

If I kint the context in my block I still get an error except if I set the annotation required = FALSE.

 *   context = {
 *     "node" = @ContextDefinition(
 *       "entity:node",
 *       label = @Translation("Current Node"),
 *       required = FALSE,
 *     )
 *   }

But the context is still empty.

Answer 1

When placing the block you have to choose from where the block will get the node value.

Select a node value

Node from URL

---

Ah! I found my own issue on DO. You also might have to unrequire the context like following:

 *   context = {
 *     "node" = @ContextDefinition(
 *       "entity:node",
 *       label = @Translation("Current Node"),
 *       required = FALSE,
 *     )
 *   }

Answer 2

So after many try, I haven't found a standalone solution for my block with the context plugin. But I found a way with a preprocess function.

Here's how I get the nid from my views row :

function comment_ajax_preprocess_views_view_fields(&$variables) {

  $block_manager = \Drupal::service('plugin.manager.block');
  $config        = ['nid' => $variables['row']->nid];
  $plugin_block  = $block_manager->createInstance('comment_block', $config);

  $variables['blockComment'] = $plugin_block->build();
}

In this preprocess function, I get the row nid and I use it in the block config.

And in my custom block:

public function build() {

  $build = [];

  $blockConfig     = $this->getConfiguration();
  $build['#theme'] = 'comment_ajax';
  $build['#nid']   = $blockConfig['nid'];

  return $build;
}

I get back the nid from the block configuration.

That works but I was looking for a way without preprocessing, just with the context.

I'm still looking for a better way :)

Answer 3

Block-plugins that inherit from BlockBase can have their context values directly set via ContextAwarePluginBase::setContextValue($key, $value). This method can be used by a preprocess function to inject context that isn't otherwise available from the route or environment.

In my case I have a block that needs a group entity in its context:

<?php

namespace Drupal\middlebury_course_hub\Plugin\Block;

use Drupal\Core\Access\AccessResult;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Session\AccountInterface;

/**
 * Provides a block with a link to the section's roster.
 *
 * @Block(
 *   id = "course_hub_roster_link",
 *   admin_label = @Translation("Roster Link"),
 *   category = @Translation("Course Hub"),
 *   context = {
 *     "group" = @ContextDefinition(
 *       "entity:group",
 *       label = @Translation("Current Group"),
 *       required = FALSE
 *     )
 *   }
 * )
 */
class RosterLinkBlock extends BlockBase {

  /**
   * {@inheritdoc}
   */
  protected function blockAccess(AccountInterface $account) {
    /** @var \Drupal\group\Entity\GroupInterface $group */
    if (($group = $this->getContextValue('group')) && $group->id()) {
      if ($group->hasPermission('view group_membership content', $account)) {
        return AccessResult::allowed();
      }
    }
    return AccessResult::forbidden();
  }

  /**
   * {@inheritdoc}
   */
  public function build() {
    // This block varies per group.
    $build['#cache']['contexts'] = ['group'];
    $build['#theme'] = 'course_hub_roster_link';
    /** @var \Drupal\group\Entity\GroupInterface $group */
    if (($group = $this->getContextValue('group')) && $group->id()) {
      $build['#group'] = $group;
    }

    // If no group was found, cache the empty result on the route.
    return $build;
  }

}

I wanted to display this block for each group entity that was a row of a view result. By adding a preprocess function to my module I could inject the group context:

/**
 * Implements hook_preprocess_hook().
 */
function middlebury_course_hub_preprocess_group(&$variables) {
  if ($variables['view_mode'] == 'dashboard_item') {
    // Add the roster-link block to the build-array.
    $block = \Drupal::service('plugin.manager.block')
               ->createInstance('course_hub_roster_link');
    $block->setContextValue('group', $variables['group']);
    if ($block->access(\Drupal::currentUser())) {
      $variables['content']['roster_link'] = $block->build();
      $variables['content']['roster_link']['#weight'] = 2;
    }
  }
}

This same technique should work for nodes as well using $block->setContextValue('node', $node); in your hook_preprocess_node function.