orm: Migrations diff and postgres schema problem with recreating existing tables

Bug Report

Q	A
BC Break	no
doctrine/annotations	v1.6.0
doctrine/dbal	v2.9.2
doctrine/migrations	v1.8.1
doctrine/orm	v2.6.3
PostgreSQL	9.6.11
PHP	7.2.15

Summary

Running doctrine:migrations:diff multiple times without any changes and with existing table in database always generate the same code trying to create table with schema and delete the very same table without schema.

How to reproduce

On any project create entity:

/**
 * @ORM\Entity(repositoryClass = "App\Domain\Repositories\UserRepository")
 * @ORM\Table(name = "users", schema = "public")
 */
class User
{

    /**
     * @ORM\Id
     * @ORM\GeneratedValue(strategy = "IDENTITY")
     * @ORM\Column(type = "integer")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length = 64, nullable = false, unique = true)
     * @var string
     */
    protected $username;

}

Run doctrine:migrations:diff

Generated migration is ok now:

$this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');

$this->addSql('CREATE TABLE public.users (id SERIAL NOT NULL, username VARCHAR(64) NOT NULL, PRIMARY KEY(id))');
$this->addSql('CREATE UNIQUE INDEX UNIQ_2552C48DF85E0677 ON public.users (username)');

Run doctrine:migrations:migrate and table is created succesfully in database.

Run doctrine:migrations:diff again and new migration is generated:

$this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');

$this->addSql('CREATE TABLE public.users (id SERIAL NOT NULL, username VARCHAR(64) NOT NULL, PRIMARY KEY(id))');
$this->addSql('CREATE UNIQUE INDEX UNIQ_2552C48DF85E0677 ON public.users (username)');
$this->addSql('DROP TABLE users');

Of course next running doctrine:migrations:migrate ends with error

relation “users” already exists

Expected behavior

I think expected behavior is clear here - don’t create new migrations when nothing was changed.