Fatal error when using a Twig defined variable as Attribute value

What happens though if you add markup like

 {% set test_attr %}
    <p>This is a test<p>
  {% endset %}

The Attribute object already filters HTML from values so that shouldn't be an issue. I believe this is covered by some tests.

Gotcha, then seems like a fine change. The test only run is also showing https://git.drupalcode.org/issue/drupal-3537801/-/jobs/5996750

1) Drupal\Tests\Core\Template\AttributeTest::testAttributeValues with data set "twig-markup" ([Twig\Markup Object (...)], ' title="foo"')
Error: Call to undefined method Twig\Markup::render()
/builds/issue/drupal-3537801/core/lib/Drupal/Core/Template/Attribute.php:329
/builds/issue/drupal-3537801/core/tests/Drupal/Tests/Core/Template/AttributeTest.php:376
ERRORS!

It working fine after adding the patch. I tested with Drupal 11.2.2
RTBC +1

I will have a look

The Needs Review Queue Bot → tested this issue. It no longer applies to Drupal core. Therefore, this issue status is now "Needs work".

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Was a clean rebase.