"Undeclared arguments passed to ViewHelper" Exception

Question

After updating TYPO3, I get a TYPO3Fluid\Fluid\Core\ViewHelper\Exception "Undeclared arguments passed to ViewHelper ... Valid arguments are."

Answer 1

Tip: Use rector to make these (and other) conversions! Functions for TYPO3 are available, see

• https://usetypo3.com/using-rector-with-typo3.html

---

This may be due to an extension using functionality that has been dropped. Using only the TYPO3 core, you should not see this error.

In your extension: If you still use the render() method in your ViewHelper class with arguments, you may want to replace this:

---

before:

public function render(Mail $mail, $type = 'web', $function = 'createAction')

---

after:

public function initializeArguments()
{
    parent::initializeArguments();

    $this->registerArgument('mail', Mail::class, 'Mail', true);
    $this->registerArgument('type', 'string', 'type: web | mail', false, 'web');
    $this->registerArgument('function', 'string', 'function: createAction | senderMail | receiverMail', false, 'createAction');
}

public function render()
{
    $mail = $this->arguments['mail'];
    $type = $this->arguments['type'] ?? 'web';
    // ...  

}

---

Additionally,

• if there is no need to use render() (e.g. unless you need to access $this variables), you may want to switch to renderStatic() for performance reasons (see also this other StackOverflow answer for clarification)
• inherit from classes in TYPO3Fluid\Fluid\Core\ViewHelper instead of TYPO3\CMS\Fluid\Core\ViewHelper:

// use TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper;
use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;

---

Documentation:

• Developing a Custom ViewHelper

Changelogs:

• Breaking: #82414 - CMS ViewHelper base classes removed
• Deprecation: #81213 - Render method arguments on ViewHelpers deprecated
• Breaking: #87193 - Deprecated functionality removed (since TYPO3 version 10)

Answer 2

You are using other extension that makes this error, for example: https://github.com/lochmueller/calendarize/issues/280

If you have a parameters in a ViewHelper, you send them as arguments from Fluid Template. In TYPO3 this error throws when in render() function not have comments about parameters. You have to include them.

Example:

<?php

namespace VENDOR\ExtensionName\ViewHelpers;

class ExampleViewHelper extends \TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper
{

 /**
  * 
  * @param int $foo
  * @return boolean
  */
 public function render($foo) {
     //function render lines    
     return $bar_boolean;
 }
}