"required" flag not available in form-element.html.twig

Problem/Motivation

The documented required variable is missing from the form-element.html.twig template variables.

The problem applies to any form with required fields (e.g. core forms, webform). The variable does not exist for non-required fields or required fields, so there is no indicator if the wrapped element is required or not.

Example: The classy template file is /core/themes/classy/templates/form/form-element.html.twig and the documentation for that shows the required variable:

required: The required marker, or empty if the associated form element is not required.

Steps to reproduce

1. Find a form with a required field
2. Print the required variable for form fields within the theme template file
3. Variable will be empty for required fields
4. Expected: Variable will be set for required fields

Proposed resolution

Debug why the required variable is not set and fix the problem.

Remaining tasks

• Debug
• Create patch
• Review patch
• Test patch
• Commit :)

User interface changes

API changes

Data model changes

Release notes snippet

Original report by @thomas.frobieter

Context:

https://api.drupal.org/api/drupal/core%21themes%21classy%21templates%21f...
says:

• "required: The required marker, or empty if the associated form element is"

Problem:

The documented "required" key / value is completely missing in the template variables of "form-element.html.twig". The problem applies to all kind of forms with required fields, core forms, webform, ...
It's neither existing für non-required fields nor for required fields. So there's no indicator at this point if the wrapped element is required or not.
The used template file is "/core/themes/classy/templates/form/form-element.html.twig".

Proposed solution:

Check why "required" flag variable is not set and correct it to be always set true / false.