laravel-custom-message-reference.md

Instead of:

product.2.type is required

Returns:

Product type N°3 is required

Or you can use some value in $values array.

public function addMessagesWithReference(array $messages)
{
    foreach ($this->request->get( self::PRODUCTS) as $key => $value){
        $referenceText = 'N°' . ($key + 1);

        $messages[ self::PRODUCTS . '.' . $key . '.name.required'] = "Product name $referenceText is required";
        $messages[ self::PRODUCTS . '.' . $key . '.type.required'] = "Product type $referenceText is required";
    }

    return $messages;
}

Idea from: https://stackoverflow.com/questions/36571628/how-to-get-array-index-in-validation-message-laravel-5-2