Traditionally, we used checkDNS like this:

AppBundle\Entity\Author:
    properties:
        bioUrl:
            - Url: { checkDNS: true }

After #23391, you must use it like this:

AppBundle\Entity\Author:
    properties:
        bioUrl:
            - Url: { checkDNS: !php/const:Symfony\Component\Validator\Constraints\Url::CHECK_DNS_TYPE_ANY }

Or use a "magic string" to define the expected non-boolean value:

AppBundle\Entity\Author:
    properties:
        bioUrl:
            - Url: { checkDNS: 'ANY' }

To me this change is a step backwards DX-wise. Why?

• It's worse for the common case where you don't care about the DNS record type.
• It's OK for the advanced case where you specify the DNS record type.
• It doesn't work for the more advanced case where you want to allow more than one DNS record type.

My proposal:

• Revert [Validator] Remove support of boolean value for the checkDNS option #23391 and don't support specifying DNS record types.
• If we still want to support this feature, define a new option called something like checkDnsType

Somewhat related to this, Fabien asked whether we should deprecate this checkDNS option entirely. See #23391 (comment)