This PR #6463 and this topic doctrine/migrations#1441 have highlighted a peculiar behavior.

In this case, let's consider the inet type, which was added to the PostgreSQL platform a long time ago -

After some tests, I noticed that in DBAL3 and DBAL4 they behave strangely. I suspect that inet was added there to work around an issue because Doctrine did not recognize this type. That is, if we have such a migration in DBAL3:

CREATE TABLE test_inet (
                id INT GENERATED BY DEFAULT AS IDENTITY NOT NULL,
                ip_inet INET NOT NULL, 
                PRIMARY KEY(id)
);

And such an entity:

#[ORM\Table(name: "test_inet")]
#[ORM\Entity]
class TestInet
{
    #[ORM\Id]
    #[ORM\Column(name: "id", type: Types::INTEGER, nullable: false)]
    #[ORM\GeneratedValue(strategy: "IDENTITY")]
    private ?int $id = null;

    #[ORM\Column(name: "ip_inet", type: Types::STRING, nullable: false)]
    private string $ipInet;
}

Then DBAL3 will ignore the fact that the migration type is INET, deciding that it is VARCHAR and will keep the type as INET. However, in DBAL4, this trick no longer works, and we have to redefine the type as follows:

doctrine:
    dbal:
        mapping_types:
            inet: override_inet

        types:
            override_inet: { class: 'App\Entity\InetType' }

#[ORM\Table(name: "test_inet")]
#[ORM\Entity]
class TestInet
{
    #[ORM\Id]
    #[ORM\Column(name: "id", type: Types::INTEGER, nullable: false)]
    #[ORM\GeneratedValue(strategy: "IDENTITY")]
    private ?int $id = null;

    #[ORM\Column(name: "ip_inet", type: 'override_inet', nullable: false)]
    private string $ipInet;
}

So, my question, what function does inet perform in initializeDoctrineTypeMappings() or other similar custom types? And isn't this a bug? Or am I using or understanding it incorrectly?

Therefore, I afraid that if the PR #6463 is applied to DBAL4 in the same way, it will not work correctly and will cause the same problems.

Thanks.