Access current node in an existing block

Question

I am using Drupal Lightning and a bootstrap subtheme. I have a requirement to place a section of the node page template in another block region. So I need to access the nodes fields in that block, fields like the taxonomy, block, breadcrumbs. Example my node--page.html.twig template prints these fields:

{{ node.title.value }}
{{ content.field_text }}
{{ drupal_view('mysection', 'block_1') }}
{{ drupal_block('mytheme_breadcrumbs') }}

It also has an includes template

{% include '@mytheme/includes/section.html.twig' %}

I can print these fields fine in a node template

node--page.html.twig

But I need to print these fields outside of the node template and into a block. I tried to create a View block and set a contextual filter "Content ID from URL" Then placed the View block in a region and then in the region template I tried to access the node fields from my region template but could not. I can access the title and body fields. This is the template.

region--myregion.html.twig

I then tried Entity blocks. I created a new block of type Entity view (Content). I tried to access the node fields from my region template but could not.

block--entityviewcontent.html.twig

Answer 1

Enable debug

by going in sites/default/ and copying the file default.services.yml to services.yml and modifying the following lines

cache: false
debug: true

Turn browser comments on

make sure your browser has Comments enabled (some browsers have them disabled by default for example in chrome in inspector on the 3 dot menu click settings and preferences find Show HTML comments

Find out which twig template is used

after that inspect the code in near the block that you want to override and you should see something similar to this

<!-- THEME DEBUG -->
<!-- THEME HOOK: 'block' -->
<!-- FILE NAME SUGGESTIONS:
   * block--block-name.html.twig
   * block--block-content--b436f9c6-34ae-4879-8b55-068015a999d3.html.twig
   * block--block-content--bundle-name.html.twig
   * block--block-content.html.twig
   * block--block-content.html.twig
   x block.html.twig
-->
<!-- BEGIN OUTPUT from 'themes/bootstrap/templates/block/block--system.html.twig' -->   

you can get the twig block template from the location in comment BEGIN OUTPUT

Use and modify template

Copy this twig file into your theme templates folder and rename to any name above. Modify the code and add something similar to the twig block template you just created

{% if nid %}
    nid:{{nid}} <br/>
    title:{{node_title}} <br/>
    body:{{body}}<br/>
    text:{{field_text}} <br/>    
{% endif %}

Expose node variable to block templates

Add into your THEMENAME.theme the following code or similar

function THEMENAME_preprocess_block(&$vars){
    $node = \Drupal::routeMatch()->getParameter('node');
    if ($node instanceof \Drupal\node\NodeInterface) {
      // You can get nid and anything else you need from the node object.
      $vars["nid"] = $node->id();
      $vars["node_title"] = $node->getTitle();
      $vars["body"] = $node->body->value;
      $vars["field_text"] = $node->field_text->value;

      //following did not work ?!
      //$vars["field_text"] = $node->get('field_text')->getValue();
      //$vars["field_text"] = $node->field_text->getValue();
    }    
}

Clear cache

with the above you are making the node fields available to block templates