File Upload doesn't create UploadedFile

Question 1

I've found a solution for the problem described in the question. Since this seems to be a problem many people have, I describe my solution in this answer.

During my research I've come across a issue on GitHub, which contains a dummy DataTransformer.

After reading the content of that page, I came up with the idea to try it with a custom DataTransformer which converts the array into an instance of UploadedFile.

Here is the step-by-step solution:

Create a DataTransformer named UploadedFileTransformer with the following source code:

use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;
use Symfony\Component\HttpFoundation\File\Exception\FileNotFoundException;
use Symfony\Component\HttpFoundation\File\UploadedFile;


class UploadedFileTransformer implements DataTransformerInterface
{
    /**
     * {@inheritdoc}
     *
     * @param array $data The array to transform to an uploaded file.
     *
     * @return \Symfony\Component\HttpFoundation\File\UploadedFile|null The
     *         uploaded file or `null` if no file has been uploaded.
     */
    public function reverseTransform($data)
    {
        if (!$data) {
            return null;
        }

        $path = $data['tmp_name'];
        $pathinfo = pathinfo($path);
        $basename = $pathinfo['basename'];

        try {
            $uploadedFile = new UploadedFile(
                $path,
                $basename,
                $data['type'],
                $data['size'],
                $data['error']
            );
        } catch (FileNotFoundException $ex) {
            throw new TransformationFailedException($ex->getMessage());
        }

        return $uploadedFile;
    }

    /**
     * {@inheritdoc}
     *
     * @param \Symfony\Component\HttpFoundation\File\UploadedFile|null $file The
     *        uploaded file to transform to an `array`.
     *
     * @return \Symfony\Component\HttpFoundation\File\UploadedFile|null The
     *         argument `$file`.
     */
    public function transform($file)
    {
        return $file;
    }
}

Update the FormType to use the UploadedFileTransformer for a file type input field (compare with the code in the question):

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class MyType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('name', 'text')
            ->add(
                $builder->create(
                    'pictureFile',
                    'file',
                    array('label' => 'Image File')
                )->addModelTransformer(new \UploadedFileTransformer)
            )
            ->add('submit', 'submit', array('label' => 'Save'));
    }

    public function getName()
    {
        return 'myentity';
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array('data_class' => __NAMESPACE__ . '\MyEntity'));
    }
}

Remove crap from the Controller, in my example the access to the Request object to obtain the uploaded file (compare with the code in the question).

$formType = new MyType;
$entity = new MyEntity;
$form = $this->formFactory->create($formType, $entity);
$form->handleRequest();

if (true === $form->isSubmitted()) {
    if (true === $form->isValid()) {
        $file = $entity->getPictureFile();

        // Persist entity, upload file to server and redirect.
    }
}

// Load View template.

And that's it. No fiddling with attributes in the FormType and the validation in the Entity is also working.

I really don't know, why this isn't the default behavior of the Symfony components? Maybe I missed to register something in my startup code?

Question 2

just add the multipart to the form and it should work

<form action="#" method="post" enctype="multipart/form-data">

</form>