Allow XML validation to be disabled but keep it enabled by default.

[jwage]

After discussing this issue, we decided to allow XML validation to be disabled for now until we have a proper solution to allow validating against custom schemas. Disabling the XML validation is the only solution available at the moment so we want to continue allowing that until we have an alternative solution to offer.

[greg0ire]

🤔 I'm wondering how the deprecation messages on 2.17.x need to be adjusted now. Maybe the flag should be made mandatory in this PR, and what would become deprecated would be to rely on the default false value (since it's going to change)? But with the bundle calling createXMLMetadataConfiguration, the flag is probably always provided anyway, with the bundle's default value. So maybe what's best is to remove the deprecation entirely, and let people find about the deprecations on 3.0.x the hard way.

[jwage]

@greg0ire Seems like we should just remove the deprecation from 2.17.x?

[greg0ire]

Maybe yes, I wonder what other maintainers think.

[jwage]

Maybe yes, I wonder what other maintainers think.

@beberlei what do you think? Can it be as simple as just backing out the deprecation for this from 2.x?

[greg0ire]

Gave it a little more thought, and I think a good solution might be to:

1. remove existing deprecations
2. add a deprecation here, if func_num_args() is 1. The deprecation should warn that the argument is going to become mandatory in 3.0.0:

   orm/lib/Doctrine/ORM/ORMSetup.php

   Line 125 in 8503469

   $config = self::createConfiguration($isDevMode, $proxyDir, $cache);

3. In DoctrineBundle, remove the default value for the config node, and in the DI extension, pass the argument to the service only if specified in the configuration. If not specified, maybe trigger another deprecation saying that the configuration node is going to become mandatory in the next major version of the bundle?
4. Change this PR so that the ORMSetup argument mentioned in point 2. becomes mandatory.
5. In the Symfony recipe, set the configuration node to true.

That way, it's fine to disable deprecations, it just has to be done explicitly.

[greg0ire]

Thanks @jwage !