Element 'css', attribute 'as': The attribute 'as' is not allowed. (CSS preloading) #18347
Description
Hi,
We want to use a technique for loading asynchronous stylesheets.
Ex. https://brianflove.com/2016/07/21/preloading-with-critical-path-css/
The issue is that link attribute "as" isn't valid according to vendor/magento/framework/View/Layout/etc/head.xsd validation file but is a officially supported HTML link attribute as described here:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/link#Attributes
Preconditions
- Magento 2.2.6
- PHP 7.1
Steps to reproduce
- I add the attribute AS on my css inclusion:
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<head>
<css src="/style.css" src_type="url" rel="preload" as="style" />
</head>
</page>- Clear cache
- Reload the front
Expected result
- Permit the AS attribute (https://developer.mozilla.org/en-US/docs/Web/HTML/Element/link#Attributes) in this file vendor/magento/framework/View/Layout/etc/head.xsd
- Add this <xs:attribute name="as" type="xs:string"/> under <xs:complexType name="linkType">
Actual result
An exception is thrown by Magento Framework 1 exception(s): Exception #0 (Magento\Framework\Config\Dom\ValidationException): Element 'css', attribute 'as': The attribute 'as' is not allowed.