Implementation of a custom linktype for the link validator

The LinkValidator uses so called "linktypes" to check for different types of links, for example internal or external links.

All "linktypes" have to implement the \TYPO3\CMS\Linkvalidator\Linktype\LinktypeInterface.

Classes implementing the LinktypeInterface are automatically registered, if autoconfigure is enabled in packages/my_extension/Configuration/Services.yaml.

Alternatively, one can manually tag a custom link type with the linkvalidator.linktype tag:

packages/my_extension/Configuration/Services.yaml

# Other definitions

MyVendor\MyExtension\Linktype\MyCustomLinktype:
  tags:
    - name: linkvalidator.linktype

Due to the autoconfiguration, the identifier has to be provided by the class directly, using the method getIdentifier().

When extending \TYPO3\CMS\Linkvalidator\Linktype\AbstractLinktype it is sufficient to set the $identifier class property.

For custom naming of a linktype, the additional interface \TYPO3\CMS\Linkvalidator\Linktype\LabelledLinktypeInterface. can be implemented, which is also part of the default AbstractLinktype implementation.

The method LabelledLinktypeInterface->getReadableName() is used to return the custom localized name of a linktype.

Example

Add new linktype

You can find the following example in the extension t3docs/examples.

Extend \TYPO3\CMS\Linkvalidator\Linktype\AbstractLinktype to create a custom linktype:

EXT:examples/Classes/LinkValidator/LinkType/ExampleLinkType.php

<?php

/*
 * This file is part of the TYPO3 CMS project. [...]
 */

namespace T3docs\Examples\LinkValidator\LinkType;

use TYPO3\CMS\Linkvalidator\Linktype\AbstractLinktype;

/**
 * This class provides Check Example Links plugin implementation
 */
class ExampleLinkType extends AbstractLinktype
{
    protected string $identifier = 'example';

    public function checkLink($url, $softRefEntry, $reference): bool
    {
        $isValidUrl = false;
        // TODO: Implement checkLink() method.
        return $isValidUrl;
    }

    public function getErrorMessage($errorParams): string
    {
        $lang = $this->getLanguageService();
        return match ($errorParams['errno'] ?? 0) {
            404 => $lang->sL('LLL:EXT:linkvalidator/Resources/Private/Language/Module/locallang.xlf:list.report.pagenotfound404'),
            // fall back to generic error message
            default => sprintf(
                $lang->sL('LLL:EXT:linkvalidator/Resources/Private/Language/Module/locallang.xlf:list.report.externalerror'),
                $errorParams['errno'],
            ),
        };
    }
}

Activate the new linktype in the page tsconfig:

EXT:examples/Configuration/TsConfig/Page/Extension/Linkvalidator.tsconfig

mod.linkvalidator {
   # specify link types to be crawled
   linktypes = db,file,external,example
}

The extension that provides the linktype must have a Configuration/Services.yaml file that contains either:

packages/my_extension/Configuration/Services.yaml

services:
  _defaults:
    autoconfigure: true

Or if autoconfiguration is not desired for some reason:

packages/my_extension/Configuration/Services.yaml

services:
  MyVendor\MyExtension\LinkValidator\LinkType\ExampleLinkType:
    tags:
      -  name: linkvalidator.linktype

Override the ExternalLinktype class

A new custom class should replace \TYPO3\CMS\Linkvalidator\Linktype\ExternalLinktype. The class inherits existing functionality from ExternalLinktype, but will be registered with the identifier "custom_external":

packages/my_extension/Classes/Linktype/ExternalLinktype.php

<?php

namespace MyVendor\NyExtension\Linktype\ExternalLinktype;

use TYPO3\CMS\Linkvalidator\LinkAnalyzer;
use TYPO3\CMS\Linkvalidator\Linktype\ExternalLinktype as LinkvalidatorExternalLinkType;

// This class inherits from ExternalLinktype,
// so it is only necessary to override some methods.
class ExternalLinktype extends LinkvalidatorExternalLinkType
{
    // This class must use a different identifier because "external" is already used.
    protected string $identifier = 'custom_external';

    public function checkLink(
        string $origUrl,
        array $softRefEntry,
        LinkAnalyzer $reference
    ): bool {
        // do additional stuff here or after parent::checkLink
        // ...
        return parent::checkLink($origUrl, $softRefEntry, $reference);
    }

    public function fetchType(array $value, string $type, string $key): string
    {
        preg_match_all(
            '/((?:http|https))(?::\\/\\/)(?:[^\\s<>]+)/i',
            (string)$value['tokenValue'],
            $urls,
            PREG_PATTERN_ORDER
        );
        if (!empty($urls[0][0])) {
            $type = $this->getIdentifier();
        }
        return $type;
    }
}

Use the new linktype:

packages/my_extension/Configuration/page.tsconfig

mod.linkvalidator.linktypes = db,file,custom_external

Since the identifier changes, the configuration should be copied to mod.linkvalidator.linktypesConfig.custom_external, so that it will be passed to the linktype, for example:

packages/my_extension/Configuration/page.tsconfig

mod.linkvalidator.linktypesConfig.custom_external < mod.linkvalidator.linktypesConfig.external