Insert custom canonical value on category page in Magento 2

Question

I've created a module to add a custom category attribute (custom canonical URL) to a category page, based on Display custom canonical URL on category page in Magento 2 question.

Here is the contents of Vendor/Module/Block/Category/CanonicalUrl.php:

<?php

namespace Vendor\Module\Block\Category;

use Magento\Store\Model\Store;

class CanonicalUrl extends \Magento\Catalog\Block\Category\View
{
    /**
     * Core registry
     *
     * @var \Magento\Framework\Registry
     */
    protected $_coreRegistry = null;

    /**
     * Catalog layer
     *
     * @var \Magento\Catalog\Model\Layer
     */
    protected $_catalogLayer;

    /**
     * @var \Magento\Catalog\Helper\Category
     */
    protected $_categoryHelper;

    /**
     * Store manager
     *
     * @var \Magento\Store\Model\StoreManagerInterface
     */
    protected $_storeManager;

    /**
     * @param \Magento\Framework\View\Element\Template\Context $context
     * @param \Magento\Catalog\Model\Layer\Resolver $layerResolver
     * @param \Magento\Framework\Registry $registry
     * @param \Magento\Catalog\Helper\Category $categoryHelper
     * @param \Magento\Store\Model\StoreManagerInterface $storeManager
     * @param array $data
     */
    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Catalog\Model\Layer\Resolver $layerResolver,
        \Magento\Framework\Registry $registry,
        \Magento\Catalog\Helper\Category $categoryHelper,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        array $data = []
    ) {
        $this->_categoryHelper = $categoryHelper;
        $this->_catalogLayer = $layerResolver->get();
        $this->_coreRegistry = $registry;
        $this->_storeManager = $storeManager;
      $this->_logger = $logger;
        parent::__construct($context, $layerResolver, $registry, $categoryHelper, $data);
    }

    /**
     * @return $this
     */
    protected function _prepareLayout()
    {
      parent::_prepareLayout();
        $this->getLayout()->createBlock(\Magento\Catalog\Block\Breadcrumbs::class);

        $category = $this->getCurrentCategory();
        if ($category) {
            $title = $category->getMetaTitle();
            if ($title) {
                $this->pageConfig->getTitle()->set($title);
            }
            $description = $category->getMetaDescription();
            if ($description) {
                $this->pageConfig->setDescription($description);
            }
            $keywords = $category->getMetaKeywords();
            if ($keywords) {
                $this->pageConfig->setKeywords($keywords);
            }
            if ($this->_categoryHelper->canUseCanonicalTag()) {
                $customCanonicalUrl = trim($category->getCustomCanonicalUrl());
                if ($customCanonicalUrl) {
                    $canonicalUrl = $this->_storeManager->getStore()->getBaseUrl() . $customCanonicalUrl;
                } else {
                    $canonicalUrl = $category->getUrl();
                }

                $this->pageConfig->addRemotePageAsset(
                    $canonicalUrl,
                    'canonical',
                    ['attributes' => ['rel' => 'canonical']]
                );
            }

            $pageMainTitle = $this->getLayout()->getBlock('page.main.title');
            if ($pageMainTitle) {
                $pageMainTitle->setPageTitle($this->getCurrentCategory()->getName());
            }
        }

        return $this;
    }
}

I implemented his answer but it isn't working for me. Inside the protected function _prepareLayout() within CanonicalUrl.php it seems $category->getCurrentCategory() seems to work because if I insert $category->getId() immediately after it, the correct Id of the category is retrieved. Also later in the code, $category->getUrl() also correctly retrieves the url of the category.

However, $category->getMetaTitle(), $category->getMetaKeywords(), and $category->getCustomCanonicalUrl() return null, so I'm unable to insert the custom_canonical_url attribute value in the category page.

Also, I notice that I'm getting the following errors in my system.log:

main.CRITICAL: Invalid template file: 'category/banner.phtml' in module: 'Example_CategoryCanonicalUrl' block's name: 'category_banner' [] []
main.CRITICAL: Invalid template file: 'category/desc_main_column.phtml' in module: 'Example_CategoryCanonicalUrl' block's name: 'category_desc_main_column' [] []

What am I doing wrong?

Answer 1

You do not state exactly what you want to use as a custom canonical value - the standard canonical url can be set by enabling "Use Canonical Link Meta Tag For Categories" in admin.

For any other custom value in the head section of a category page you can add this via catalog_category_view.xml layout.

Module MyModule_Seo:

MyModule/Seo/registration.php

<?php
    \Magento\Framework\Component\ComponentRegistrar::register(
        \Magento\Framework\Component\ComponentRegistrar::MODULE,
        'MyModule_Seo',
        __DIR__
    );

MyModule/Seo/view/frontend/layout/catalog_category_view.xml

<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="2columns-left" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <referenceBlock name="head.additional">
            <block class="Magento\Catalog\Block\Category\View" name="custom.category" template="MyModule_Seo::catalog/view/custom/category.phtml"></block>
        </referenceBlock>
    </body>
</page>

MyModule/Seo/frontent/templates/catalog/view/custom/category.phtml

<meta property="mymodule:custom" content="custom-content-for-<?= $block->escapeUrl($block->getCurrentCategory()->getName()) ?>" />

If you want to perform some extra logic based on $block->getCurrentCategory() data pass the object into a ViewModel help class and perform the logic and return the data to your template.

Answer 2

Turns out the "invalid template file" errors were the clue to the problem (imagine that). To resolve, I merely copied those templates:

From app/design/ThemeVendor/Theme/Magento_Catalog/templates/category

To app/code/Vendor/Module/view/frontend/templates/category

Works like a charm now. :)