Symfony 3.4 FileType集合添加了原型：文件字段未呈现

Question

我有一个ProductType表单，其中有Collection个ProductImageType（用于上传）。通过原型，我定义了一个视图并使用Javascript添加了新元素。

问题是，单击Add时会找到并渲染原型视图，但是ProductImageType中的表单小部件根本无法渲染。

这是我代码的相关部分。

发生的是，如果我向表单中添加其他字段（例如，非映射字段仅用于测试目的），则呈现product/prototype.images.html.twig内的代码，除了FileType的表单字段外此视图不会显示。

其他项目中也一直在使用类似的代码。

ProductType

class ProductType extends AbstractType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('category'   , null, ['label' => "Category", 'attr' => ['placeholder' => "Seleccione una categoría"]])
                ->add('name'       , null, ['label' => "Title"])
                ->add('description', null, ['label' => "Description", 'attr' => ['class' => 'product-description-edit-field']])
                ->add('images'     , CollectionType::class, [
                                        'label' => 'false',
                                        'entry_type' => ProductImageType::class,
                                        'allow_add' => true,
                                        'allow_delete' => true,
                                        // 'delete_empty' => true,
                                        'prototype'    => true,
                                        'prototype_data' => New ProductImage
                ])
        ;
    }/**

ProductImageType

class ProductImageType extends AbstractType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
                ->add('image', FileType::class, ['label' => "Upload a picture",
                                                 // 'data_class' => null,
                                                 'attr' => ['class' => ''],
                                                ]);
    }

edit.html.twig

{# ... #}
{{ form_row(edit_form.images) }}
<ul id="edit-image-list" class="edit-image-list" data-prototype="{% filter escape %}
            {{ include('product/prototype.images.html.twig', { 'form': edit_form.images.vars.prototype }) }}
        {% endfilter %}">
    {# iterate over each existing image and render its only field: name #}
    {% for image in edit_form.images %}
        <li>{{ form_row(image.image) }}</li>
    {% endfor %}
</ul>

<div class="button-wrapper left">
    <a href="javascript:void(0)" class="btn btn-sm btn-outline-success" onclick="addImageUploader()">
        Add image
    </a>
</div>
{# ... #}
<script type="text/javascript">
function addImageUploader()
{
    // Get the data-prototype explained earlier
    var prototype = $('#edit-image-list').data('prototype');

    // get the new index
    var index = $('#edit-image-list li').length;

    // Replace '__name__' in the prototype's HTML to instead be a number based on how many items we have
    var newForm = prototype.replace(/__name__/g, index);

    $('#edit-image-list').append(newForm);
}
</script>

product / prototype.images.html.twig

<li>
    <div class="row">
        <div class="col-md-8">
            {{ form_row(form.image, {'attr': {'class': 'form-control'}}) }}
        </div>
        <div class="col-md-4">
            <a href="https://via.placeholder.com/150"><img src="https://via.placeholder.com/150"></a>
        </div>
    </div>
</li>

产品实体

/**
 * @ORM\Entity
 */
class Product
{
    /**
     * @ORM\OneToMany(targetEntity="ProductImage", mappedBy="product", cascade={"persist", "remove"})
     */
    private $images;

    public function __construct()
    {
        $this->images = new \Doctrine\Common\Collections\ArrayCollection();
    }

ProductImage实体

/**
 * @ORM\Entity
 */
class ProductImage
{

    /**
     * @ORM\Column(type="string", length=255, nullable=true)
     * @Assert\Image()
     */
    private $image;