fix(symfony): clear SkolemIriConverter state between requests via ResetInterface

[gwini]

Q	A
Branch?	4.2
Tickets
License	MIT
Doc PR

SkolemIriConverter uses SplObjectStorage $objectHashMap and array $classHashMap to cache IRI mappings for non-entity objects during serialization. In long-running processes (FrankenPHP worker mode,
Swoole, RoadRunner), these maps accumulate entries across requests and are never cleared, causing a memory leak.

How I found it

Running Symfony 7.4 with API Platform 4.2.20 in FrankenPHP worker mode, I observed ~2.7 MB/request memory growth when calling an endpoint that serializes ~665 DTO objects (each containing two CarbonImmutable
properties). Memory grew linearly with every request and was never reclaimed by GC.

Using a deep object-graph scanner with reflection across all container services, I traced the leaked references to SkolemIriConverter::$objectHashMap — it held strong references to every serialized DTO and
its nested objects across all previous requests. The class never implements ResetInterface, so services_resetter never clears it.

After applying this fix, memory stabilized at ~76 MB across 20+ consecutive requests.

Changes

• SkolemIriConverter now implements ResetInterface with a reset() method that clears both $objectHashMap and $classHashMap
• The service is tagged with kernel.reset so Symfony automatically calls reset() between requests

Note: The Laravel variant (ApiPlatform\Laravel\Routing\SkolemIriConverter) has the same issue — its $objectHashMap and $classHashMap also grow unbounded across requests when running under Octane or other
long-running setups. I'm not familiar enough with Laravel's service lifecycle to implement the correct reset mechanism there. A follow-up PR for the Laravel side would be appreciated.