Module theme hook template works only after hard refresh

Question

I have a custom module named abc to simplify explaining this issue:

modules/custom/abc/abc.module:

function abc_theme($existing, $type, $theme, $path) {
  return [
    'abc' => [
      'variables' => [
        'data' => [],
      ],
    ],
  ];
}

modules/custom/abc/src/Plugin/Block/AbcBlock.php:

/**
 * Provides a 'ABC' Block.
 *
 * @Block(
 *   id = "abc_block",
 *   admin_label = @Translation("Abc Block"),
 *   category = @Translation("Content"),
 * )
 */
class AbcBlock extends BlockBase {

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

    return [
      '#theme' => 'abc',
      '#data' => ['foo' => 'bar'],
      '#cache' => [
        'tags' => ['dehs'],
      ],
    ];
  }
}

modules/custom/abc/templates/abc.html.twig:

{{ foo }}

When I run drush cr, abc.html.twig renders on the page. However, when I click Rebuild Cache [/rebuild-cache-access/rebuild-cache?token=] from admin toolbar, the block doesn't render. Error logs: Theme hook abc not found.

After that I run drush cr again and the template appears again. Why does it lose reference to template after in-browser Rebuild Cache, and then works again when I run 'drush cr'?

One more thing: If I move the abc_theme() from abc.module to my default .theme (along with abc.html.twig), Rebuild Cache link doesn't cause the error. Simple solution would be to keep abc.html.twig in the theme, however, I have a specific functionality that is generated with abc module and I would like to keep all relating hooks inside the abc module. What gives?

Answer 1

The project is running on Lando Docker local setup. I ended up running lando rebuild and that seemed to resolved the problem. It could have been file permission as @4uk4 suggested.