EmailTemplateSniff.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magento2\Sniffs\Legacy;

use PHP_CodeSniffer\Files\File;
use PHP_CodeSniffer\Sniffs\Sniff;

/**
 * Test for obsolete email directives in view/email/*.html
 */
class EmailTemplateSniff implements Sniff
{
    private const OBSOLETE_EMAIL_DIRECTIVES = [
        '/\{\{htmlescape.*?\}\}/i' => 'Directive {{htmlescape}} is obsolete. Use {{var}} instead.',
        '/\{\{escapehtml.*?\}\}/i' => 'Directive {{escapehtml}} is obsolete. Use {{var}} instead.',
    ];

    private const ERROR_CODE = 'FoundObsoleteEmailDirective';

    /**
     * @inheritdoc
     */
    public function register(): array
    {
        return [
            T_INLINE_HTML
        ];
    }

    /**
     * @inheritDoc
     */
    public function process(File $phpcsFile, $stackPtr)
    {
        $content = $phpcsFile->getTokens()[$stackPtr]['content'];
        foreach (self::OBSOLETE_EMAIL_DIRECTIVES as $directiveRegex => $errorMessage) {
            if (preg_match($directiveRegex, $content)) {
                $phpcsFile->addError(
                    $errorMessage,
                    $stackPtr,
                    self::ERROR_CODE
                );
            }
        }
    }
}