Multiple inheritance with doctrine not detected and implemented in migration

[rv2931]

Hello,
I've already use multiple inheritance with doctrine class A inherits class B that inherits class C
According to the logic and to my mermories in this case, doctrine must create one discriminator column in C and B
But when I do it, doctrine only (or at least migration tool) only creates one discriminator column in C, not in B
I think there a problem even if everything comiles with success
My Symfony code to reproduce
If someone can confirm that I'm right and there a problem if my migration that only create one discr column in MyParent class
Thank you in advance
RV

<?php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use App\Repository\MyParentRepository;
use Doctrine\ORM\Mapping as ORM;
use App\Entity\MyChild;

/**
 * @ApiResource()
 * @ORM\Entity(repositoryClass=MyParentRepository::class)
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="discr", type="string")
 * @ORM\DiscriminatorMap({"child"="MyChild"})
 */
class MyParent
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $parentAttribute;

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getParentAttribute(): ?string
    {
        return $this->parentAttribute;
    }

    public function setParentAttribute(string $parentAttribute): self
    {
        $this->parentAttribute = $parentAttribute;

        return $this;
    }
}

<?php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use App\Repository\MyChildRepository;
use Doctrine\ORM\Mapping as ORM;
use App\Entity\MyChildChild;
use App\Entity\MyParent;

/**
 * @ApiResource()
 * @ORM\Entity(repositoryClass=MyChildRepository::class)
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="discr", type="string")
 * @ORM\DiscriminatorMap({"childchild"="MyChildChild"})
 */
class MyChild extends MyParent
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $childAttribute;

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getChildAttribute(): ?string
    {
        return $this->childAttribute;
    }

    public function setChildAttribute(string $childAttribute): self
    {
        $this->childAttribute = $childAttribute;

        return $this;
    }
}

<?php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use App\Repository\MyChildChildRepository;
use Doctrine\ORM\Mapping as ORM;
use App\Entity\MyChild;

/**
 * @ApiResource()
 * @ORM\Entity(repositoryClass=MyChildChildRepository::class)
 */
class MyChildChild extends MyChild
{

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $MyChildChildAttribute;

    public function getMyChildChildAttribute(): ?string
    {
        return $this->MyChildChildAttribute;
    }

    public function setMyChildChildAttribute(string $MyChildChildAttribute): self
    {
        $this->MyChildChildAttribute = $MyChildChildAttribute;

        return $this;
    }
}

<?php

declare(strict_types=1);

namespace DoctrineMigrations;

use Doctrine\DBAL\Schema\Schema;
use Doctrine\Migrations\AbstractMigration;

/**
 * Auto-generated Migration: Please modify to your needs!
 */
final class Version20210922133036 extends AbstractMigration
{
    public function getDescription(): string
    {
        return '';
    }

    public function up(Schema $schema): void
    {
        // this up() migration is auto-generated, please modify it to your needs
        $this->addSql('CREATE TABLE my_child (id INT NOT NULL, child_attribute VARCHAR(255) NOT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 COLLATE `utf8mb4_unicode_ci` ENGINE = InnoDB');
        $this->addSql('CREATE TABLE my_child_child (id INT NOT NULL, my_child_child_attribute VARCHAR(255) NOT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 COLLATE `utf8mb4_unicode_ci` ENGINE = InnoDB');
        $this->addSql('CREATE TABLE my_parent (id INT AUTO_INCREMENT NOT NULL, parent_attribute VARCHAR(255) NOT NULL, discr VARCHAR(255) NOT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 COLLATE `utf8mb4_unicode_ci` ENGINE = InnoDB');
        $this->addSql('ALTER TABLE my_child ADD CONSTRAINT FK_4E75E6EDBF396750 FOREIGN KEY (id) REFERENCES my_parent (id) ON DELETE CASCADE');
        $this->addSql('ALTER TABLE my_child_child ADD CONSTRAINT FK_832072F2BF396750 FOREIGN KEY (id) REFERENCES my_parent (id) ON DELETE CASCADE');
    }

    public function down(Schema $schema): void
    {
        // this down() migration is auto-generated, please modify it to your needs
        $this->addSql('ALTER TABLE my_child DROP FOREIGN KEY FK_4E75E6EDBF396750');
        $this->addSql('ALTER TABLE my_child_child DROP FOREIGN KEY FK_832072F2BF396750');
        $this->addSql('DROP TABLE my_child');
        $this->addSql('DROP TABLE my_child_child');
        $this->addSql('DROP TABLE my_parent');
    }
}

[rv2931]

For the doctrine side, the normal way is the the discriminator is only created in the top most table, not intermediate. So it seems not to be a doctrine problem
issue to be closed
/close