Magento2.Templates.HelperInTemplate Rule

[diazwatson]

After the work done in #108 I kept wondering:

• Why we include this rule in ThisInTemplateSniff?
• Why not create a separate HelperInTemplateSniff to check for the use of helpers in PHTML files?
• Should we also explain how to create a ViewModel or is enough mentioning how to use it in the template?
• How about adding a link to the DevDocs to explain how to create the viewModel?

This is a proposal to answer those questions.

Rule

The use of helpers is in general discouraged. For PHTML, consider using ViewModel instead.

Reason

The use of helpers is in general discouraged therefore any $this->helper(<helper_class>) code used in PHTML templates should be refactored. Consider using ViewModel instead.

Implementation

Typical example of a helper being used in a PHTML:

<?php $_incl = $block->helper(<helper_class>)->...; ?>

Once the ViewModel is created, call it in the PHTML as follow:

<?php $viewModel = $block->getViewModel(); ?>

or

<?php $viewModel = $block->getData('viewModel'); ?>