Directly placing Drupal blocks in a Twig file

direct_print

{#
  I suspect Drupal site builders will eventually to be able
  to put block instances into twig files without being limited
  to a theme's regions.  Calling a function to print them
  anywhere is farirly simple.
#}
{{ drupal_block_placement('bartik_breadcrumbs') }}

patch

diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index 4cb31ca..47618a0 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -27,6 +27,7 @@ class TwigExtension extends \Twig_Extension {
   public function getFunctions() {
     return array(
       new \Twig_SimpleFunction('url', 'url'),
+      new \Twig_SimpleFunction('drupal_block_placement', 'block_get_render_array_by_machine_name'),
       // This function will receive a renderable array, if an array is detected.
       new \Twig_SimpleFunction('render_var', 'twig_render_var'),
     );
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 5190436..abd45f8 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -449,3 +449,27 @@ function block_language_entity_delete(Language $language) {
     }
   }
 }
+
+/**
+ * Return the render array for a block instance.
+ *
+ * The function is used in conjunction with Twig to be able to call in a Twig
+ * file something like {{ drupal_block_placement('machine_name_of_block') }}
+ *
+ * @todo, this code should probably go into a service rather than adding another
+ * procedural function.
+ *
+ * @param string $machine_name
+ *   The machine name of a block instance like 'poweredbydrupal_2' or
+ *   'views_block__content_recent_block_1'
+ * @return array
+ *   A render array from entity_view()
+ */
+function block_get_render_array_by_machine_name($block_machine_name) {
+
+  $entity = entity_load('block', $block_machine_name);
+  $view = entity_view($entity, 'default');
+
+  return $view;
+}
+
diff --git a/core/themes/bartik/templates/page.html.twig b/core/themes/bartik/templates/page.html.twig
index b075295..22bd591 100644
--- a/core/themes/bartik/templates/page.html.twig
+++ b/core/themes/bartik/templates/page.html.twig
@@ -162,6 +162,13 @@
             {{ action_links }}
           </ul>
         {% endif %}
+
+      {#
+        Directly place the breadcrumb block in a twig file. This technique
+        skips over placing the block in a region.
+      #}
+      {{ drupal_block_placement('bartik_breadcrumbs') }}
+
       {{ page.content }}
       {{ feed_icons }}
     </section></main> <!-- /.section, /#content -->