Introduce a @Depth annotation

[dunglas]

When serializing trees with groups such as the following, it is convenient to be able to configure the Serialization depth:

class TreeEntry
{
    /**
      * @var TreeEntry
      * @Groups{"a"}
      */
    public $parent;
}

A new @Depth(n) where N is the maximum depth level to normalize can be useful for such use case. When n is reached, the normalizer will output the IRI of the resource instead of embedding it. Proposal:

class TreeEntry
{
    /**
      * @var TreeEntry
      * @Groups{"a"}
      * @Depth(2)
      */
    public $parent;
}

[dunglas]

Alternative:

• Introduce the Depth annotation directly in the Symfony Serializer component
• Add a handler system similar to the circular reference handler
• Register a custom handler outputting an IRI in the bundle

[SoboLAN]

If the depth of the objects is higher than the specified value in @Depth annotation, then how will the output look like ?

Also, the next step the Serializer will do after normalizing is encoding. In that case, wouldn't the encoding step fail ?

[dunglas]

• In Symfony, it will work like for circular reference: allow to register a \Callable as handler, the default callable throw an exception
• The bundle will register a custom handler outputting the IRI of the relation
• Because of the previous, it will the encoding will be OK in the bundle

[MLKiiwy]

Really good idea, maybe add also this option in normalization / denormalization context ?

[Drachenkaetzchen]

+1 from me. @Depth is pretty much essential for serializing trees.

[theofidry]

@dunglas any update regarding this feature?

[sroze]

Done in symfony/symfony#17113