Unable to save entity with CollectionType if unique constraint and reorder

[Seb33300]

For instance, we have 2 entities: Website and Domain.
Website have a OneToMany relation to Domain:

@ORM\OneToMany(targetEntity="Domain", mappedBy="domain", cascade={"all"}, orphanRemoval=true)
@Assert\Valid

And Domain have a ManyToOne relation and a unique constraint on the domain name field:

@UniqueEntity("name", message="Domain already exists.")

@ORM\Column(name="name", type="string", unique=true)
@Assert\NotBlank(message = "Domain required.")
$name

@ORM\ManyToOne(targetEntity="Website", inversedBy="domains")
@ORM\JoinColumn(name="website_id", referencedColumnName="id", nullable=false)
@Assert\NotBlank(message = "Website required.")
$website

I have 2 forms: WebsiteType and DomainType.
WebsiteType have a CollectionType of DomainType:

$builder
    ->add('domains', CollectionType::class, array(
        'entry_type'   => DomainType::class,
        'allow_add'    => true,
        'allow_delete' => true,
        'by_reference' => false,
    ))
;

I can save a new website with domains automatically created.
I can update website and domains in the same form too.

The problem is on an update, if we do not send domains in the same order then they have been saved, it will raise an error on the Domain unique constraint.

Example:
Create a new website with 2 domains:

• domain[0][name] = domain1.com
• domain[1][name] = domain2.com

Save it: OK

Update the website on the same form (changing domain order):

• domain[0][name] = newdomain.com
• domain[1][name] = domain1.com

Save it: ERROR: Unique constraint on domain name, domain1.com already exist

Update the website on the same form (without changing order):

• domain[0][name] = domain1.com
• domain[1][name] = newdomain.com

Save it: OK

[HeahDude]

Hi @Seb33300, I think it's a duplicate of #7468

[javiereguiluz]

Closing it as duplicated, as explained by @HeahDude.

@Seb33300 for now, the solution would be to define a setDomains() method and use it instead of addDomain() as explained in the comments of #7468.