Improve InvalidComponentException by including the parent/calling Twig template path

Problem/Motivation

When a Single Directory Component (SDC) fails prop validation during development, Drupal throws an InvalidComponentException. However, the generated stack trace is often notoriously difficult to debug because the underlying compiled Twig classes are only listed as hashes (e.g., __TwigTemplate_37dfef847a6375fdc2b31820ed3a5cd2).

The error message states which component failed, but completely conceals where (in which parent theme/module Twig file) that component was actually embedded or included. In complex layouts with highly nested components, finding the culprit becomes a guessing game.

In our case this was the (not very helpful) error message shown
Drupal\Core\Render\Component\Exception\InvalidComponentException: [radix:card/card_subtitle] NULL value found, but a string or an object is required. This may be because the property is empty instead of having data present. If possible fix the source data, use the |default() twig filter, or update the schema to allow multiple types.. [radix:card/card_subtitle_utility_classes] NULL value found, but an array or an object is required. in Drupal\Core\Theme\Component\ComponentValidator->validateProps() (line 243 of core/lib/Drupal/Core/Theme/Component/ComponentValidator.php).

Steps to reproduce

Have a broken / incompatible SDC call, e.g. by updating theme. We had this several times updating Radix for example, but I guess there are several ways to experience this.

Proposed resolution

Enhance Drupal\Core\Template\ComponentsTwigExtension::doValidateProps() to intercept the InvalidComponentException. Inside the catch block, we can inspect the debug_backtrace() to find the first Twig\Template instance that is not the component template itself. By utilizing Twig's native getTemplateName() method, we can extract the precise file path of the calling template and prepend it to the exception message.
Remaining tasks

The result of the fix is
Drupal\Core\Render\Component\Exception\InvalidComponentException: Component validation failed in Twig file [themes/custom/my_theme/templates/content/taxonomy-term--card.html.twig] for component [radix:card]: [radix:card/card_subtitle] NULL value found, but a string or an object is required. This may be because the property is empty instead of having data present. If possible fix the source data, use the |default() twig filter, or update the schema to allow multiple types.. [radix:card/card_subtitle_utility_classes] NULL value found, but an array or an object is required. in Drupal\Core\Template\ComponentsTwigExtension->doValidateProps() (line 152 of core/lib/Drupal/Core/Template/ComponentsTwigExtension.php).
which shows the affected twig templates and helps fixing the issue efficiently.

Remaining tasks

1. Discuss
2. Implement
3. Review
4. Release

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet