Render block via twig template

Question

I have programmatically created a block. In my module folder I added all suggested templates in a templates folder(mymodule/templates/suggestedtemplatename.html.twig).

However the block is not using any of them! I have enabled the theme debugger which gives me all the suggestions and describes which part of the page is produced from which template. I can see only block.html.twig producing html. I tried drush cr and uninstalling/installing the module

Answer 1

I was missing the implementation of hook_theme. In order to use the template you need to declare it there. FX

/**
 * Implements hook_theme().
*/
function mymodule_theme() {
  return array(
    'block__newsletter' => array(
      'render element' => 'elements',
    ),
  );
}

You should then have a templates/block--newsletter.html.twig.