[Issue] fix: remove dead libxml_set_external_entity_loader guard in Config Dom

[m2-assistant]

This issue is automatically created based on existing pull request: #40944: fix: remove dead libxml_set_external_entity_loader guard in Config Dom

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Description

Remove the dead libxml_set_external_entity_loader() availability guard from Magento\Framework\Config\Dom::validateDomDocument().

Problem

The method starts with a guard that is always false:

if (!function_exists('libxml_set_external_entity_loader')) {
    return [];
}

libxml_set_external_entity_loader() is provided by ext-libxml, which is bundled with PHP and cannot be disabled; the function has existed since PHP 5.4. Since Magento requires PHP 8.3+, this branch is unreachable.

Worse, if the branch were ever taken it would return an empty error list — silently skipping XSD schema validation entirely and reporting the document as valid.

Solution

Remove the dead guard. Behavior on every supported PHP version is unchanged.

Files Changed

• lib/internal/Magento/Framework/Config/Dom.php

Related Pull Requests

Same cleanup pattern as #40686, #40687, #40688.

Manual testing scenarios (*)

1. Run lib/internal/Magento/Framework/Config/Test/Unit/DomTest.php — all validation tests pass.
2. Run the Magento/Framework/Config integration suite — schema validation behaves as before.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[github-jira-sync-bot]

✅ Jira issue https://jira.corp.adobe.com/browse/AC-17626 is successfully created for this GitHub issue.