Problem of relation called twice on apiplatform with symfony - api

Question

I have two entities: Tag, Post.
In relation Many to Many
I have an API route in GET: /api/tags/{id}
I want to return the posts associated to a tag by the tag.
But I also want to return the tags associated with the posts objects returned by the Tag.
This produces an error:
"The total number of joined relations has exceeded the specified maximum. Raise the limit if necessary with the "api_platform.eager_loading.max_joins" configuration key (https://api-platform.com/docs/core/performance/#eager-loading), or limit the maximum serialization depth using the "enable_max_depth" option of the Symfony serializer (https://symfony.com/doc/current/components/serializer.html#handling-serialization-depth)."
The tag entity :
#[ApiResource(
normalizationContext: ['groups' => ['read:collection:Tag']],
collectionOperations:['get'],
paginationEnabled: false,
itemOperations: [
'get' => [
'normalization_context' => ['groups' => [
'read:item:Tag',
'read:collection:Tag'
]]
],
]
)]
class Tag
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
#[Groups(['read:collection:Post', 'read:item:Category', 'read:collection:Tag'])]
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
#[Groups(['read:collection:Post', 'read:item:Category', 'read:collection:Tag'])]
private $name;
/**
* #ORM\ManyToMany(targetEntity=Post::class, mappedBy="tags")
*/
#[Groups(['read:item:Tag'])]
private $posts;
The tag field in the Post entity :
/**
* #ORM\ManyToMany(targetEntity=Tag::class, inversedBy="posts")
*/
#[Groups(['read:collection:Post', 'read:item:Category','read:item:Tag'])]
private $tags;
I tried limiting the maximum serialization depth using the "enable_max_depth" option as indicated in the error message, it does not work.

Answer 1

I have encountered this problem for a many-to-many relationship when the same serialization group is used for both the entity's relationship property as well as the property that relates back from the associated entity.
In your case, I think you need to remove the read:item:Tag group from the $tags property on the Post entity.
/**
* #ORM\ManyToMany(targetEntity=Tag::class, inversedBy="posts")
*/
#[Groups(['read:collection:Post', 'read:item:Category'])]
private $tags;
I realize this may affect how data is retrieved from the posts endpoint, but it seems to be necessary for relationships in order to avoid recursion. Group infrastructure can get confusing.