Sonata Media - file extension validation in admin - php

Question

I just want to validate the extension of image that I upload in Sonata Admin (v3.28.0) with Sonata Media Bundle (v3.10.0) in Symfony (v2.8.32) application.
I've read all similar questions and Sonata documentations, but still don't have a success.
I tried to add constraints to config.yml
sonata_media:
providers:
image:
allowed_extensions:
- 'jpg'
- 'png'
I wonder that it doesn't work as is, because standard FileProvider (that is extended by ImageProvider) has extension check in validate method. But the method is not being called.
So I also tried to create custom provider:
services.yml:
sonata.media.provider.custom:
class: Application\Sonata\MediaBundle\Provider\CustomImageProvider
tags:
- { name: sonata.media.provider }
arguments:
- sonata.media.provider.custom
- #sonata.media.filesystem.local
- #sonata.media.cdn.server
- #sonata.media.generator.default
- #sonata.media.thumbnail.format
- ['jpg', 'png']
- ['image/pjpeg', 'image/jpeg', 'image/png', 'image/x-png']
- #sonata.media.adapter.image.imagick
- #sonata.media.metadata.proxy
calls:
- [ setTemplates, [{helper_view:SonataMediaBundle:Provider:view_image.html.twig,helper_thumbnail:SonataMediaBundle:Provider:thumbnail.html.twig}]]
Application\Sonata\MediaBundle\Provider\CustomImageProvider.php:
<?php
namespace Application\Sonata\MediaBundle\Provider;
use Sonata\CoreBundle\Validator\ErrorElement;
use Sonata\MediaBundle\Model\MediaInterface;
use Sonata\MediaBundle\Provider\ImageProvider;
class CustomImageProvider extends ImageProvider
{
public function validate(ErrorElement $errorElement, MediaInterface $media)
{
throw new \Exception();
}
}
config.yml:
sonata_media:
contexts:
image:
providers:
- sonata.media.provider.custom
formats:
small: { width: 100 , quality: 70}
big: { width: 500 , quality: 70}
But the validate method is still not being called.
So when I try to load GIF image I get an error:
Length of either side cannot be 0 or negative, current size is x
Do I miss something?
UPDATE
Simple validation can be added right in SomeEntityAdmin class like this:
public function validate(ErrorElement $errorElement, $object)
{
/** #var Media $image */
$image = $object->getImage();
if (!in_array($video->getContentType(), ['image/pjpeg', 'image/jpeg', 'image/png', 'image/x-png'])) {
$errorElement
->with('image')
->addViolation('Invalid file type')
->end()
;
};
}
But it's not a good solution if you want to validate a batch of uploaded images.