我的symfony应用程序有此实体：

<?php

namespace App\Entity;

class Lead
{
    private ?string $zipCode;
    private ?string $city;

    public function getZipCode(): ?string
    {
        return $this->zipCode;
    }

    public function setZipCode(string $zipCode): self
    {
        $this->zipCode = $zipCode;

        return $this;
    }

    public function getCity(): ?string
    {
        return $this->city;
    }

    public function setCity(string $city): self
    {
        $this->city = $city;

        return $this;
    }
}

表格LeadType为：

$builder->add('zipCode', TextType::class, [
        'attr' => [
            'placeholder' => 'Ex : 44000',
            'onchange' => 'cityChoices(this.value)',
        ]
    ])
    ->add('city', ChoiceType::class, [
        'choices' => [],
        'attr' => ['class' => 'form-control'],
        'choice_attr' => function () {return ['style' => 'color: #010101;'];},
    ]);

当用户输入邮政编码时，javascript函数 * cityChoices（）* 使用外部API添加选择选项，如：

我的问题是控制器中的表单是无效的。因为用户选择了一个城市，而这个城市在LeadType的选项中没有提供（'choices'=〉[]）。
下面是错误：

0 => Symfony\Component\Form\FormError {#3703 ▼
          #messageTemplate: "The selected choice is invalid."
          #messageParameters: array:1 [▼
            "{{ value }}" => "Bar-le-Duc"
          ]

如何使选择有效？