serializer.md

Serializer

With symfony/serializer installed, the bundle registers GraphqlEntityNormalizer. It writes the entities whose fields are not all loaded without loading them:

• a relation loaded on first access (GraphqlOrm\Fetch::Lazy, or lazy_loading) and not read yet is written as its identifier;
• a partial entity, hydrated from a selection of its fields, is written with its selected fields only, the others left out even when they have a default value: "done": false would contradict the API for a task that is done.

$tasks = $taskRepository->findAll(); // Task::$assignee mapped with GraphqlOrm\Fetch::Lazy

return $this->json($tasks);
// [{"id": 1, "title": "Write the docs", "assignee": {"id": 7}}, ...]: no query for the assignees

Without it, the ObjectNormalizer reads every property, and so loads each lazy relation with a query of its own (an N+1 problem hidden in a JSON response), or fails on a field the query did not select.

The entities held in full are left to the other normalizers, ObjectNormalizer included, with their groups, name converters and context as usual. GraphqlEntityNormalizer writes the mapped properties already loaded only, under their PHP names, without groups nor name converters; their values (a loaded relation, a date...) go through the other normalizers. Select the relations you want written in full (raise max_depth, or select their fields with the query builder).

The profiler counts, in its "Serializer" tab, the relations written as identifiers and the partial entities written, and warns about the lazy loads sent while the serializer was writing an entity: the N+1 problem above, when another normalizer reads the relations.