yii2: Adding common validation error (not related with particular attribute)

When writing a custom validation, we need to use addError method of yii\base\Model (if we write it in model) or yii\validators\Validator (if we write separate validator).

Both methods require $attribute parameter (attribute name) to be passed, and as we can see from the sources, we can’t leave it blank:

addError of yii\base\Model:

/**
 * Adds a new error to the specified attribute.
 * @param string $attribute attribute name
 * @param string $error new error message
*/
public function addError($attribute, $error = '')
{
    $this->_errors[$attribute][] = $error;
}

addError of yii\validators\Validator:

/**
 * Adds an error about the specified attribute to the model object.
 * This is a helper method that performs message selection and internationalization.
 * @param \yii\base\Model $model the data model being validated
 * @param string $attribute the attribute being validated
 * @param string $message the error message
 * @param array $params values for the placeholders in the error message
*/
public function addError($model, $attribute, $message, $params = [])
{
    $params['attribute'] = $model->getAttributeLabel($attribute);
    if (!isset($params['value'])) {
        $value = $model->$attribute;
        if (is_array($value)) {
            $params['value'] = 'array()';
        } elseif (is_object($value) && !method_exists($value, '__toString')) {
            $params['value'] = '(object)';
        } else {
            $params['value'] = $value;
        }
    }
    $model->addError($attribute, Yii::$app->getI18n()->format($message, $params, Yii::$app->language));
}

Possible options:

1) Select the most important relevant field and add error to it.

2) Select multiple important relevant fields and add the same error message to them (we can store and pass message in separate variable before passing to keep code DRY).

3) We can use not existing attribute name for adding error, let’s say all, because attribute existence is not checked at that point.

class YourForm extends \yii\base\Model
{
    /**
     * @inheritdoc
     */
    public function rules()
    {
        return [
            ['name', 'yourCustomValidationMethod'],
        ];
    }        

    /**
     * @return boolean
     */
    public function yourCustomValidationMethod()
    {
        // Perform custom validation here regardless of "name" attribute value and add error when needed
        if (...) {
            $this->addError('all', 'Your error message');
        }            
    }
}

Note that we still need to attach validator to existing attribute(s) (otherwise exception will be thrown). We can use the most relevant attribute.

As a result, we will see error only in error summary. We can display error summary in form like that:

<?= $form->errorSummary($model) ?>

But in most cases there are always one or multiple attributes related with error so we can use option 1 or 2. Option 3 is kind of hack but I think it’s pretty good workaround for that problem.

Please also see this related question and my answer on StackOverflow, basically the text above was taken from there.

Bottom line, I think we either need:

1) Add support for adding common validation errors. For example Django has support for that. 2) If you find implementing this ambiguous or not necessary because it goes against some framework philosophy or principles, I think the solution described in option 3 proves that validation errors implementation is a bit inconsistent in terms of passing attribute.

• We can’t pass not existing attribute when declaring validation rule.
• But we can’t easily add error for non existing attribute.

At least we can get rid of that.

Also according docs section would be helpful.