API Platform 4.3 — State Providers

Use when

• A Get / GetCollection operation needs a transformation between the data source and the API representation.
• You want to decorate the Doctrine read pipeline (e.g. to add audit logging or shape an Output DTO).
• A response payload depends on a request header (versioning, locale).
• A Resource is backed by a non-Doctrine source (external API, in-memory store, search engine).

Default workflow

1. Scaffold with php bin/console make:state-provider.
2. Inject the Doctrine item / collection providers via #[Autowire(service: '…')] (modern decoration pattern).
3. Discriminate collection vs item with $operation instanceof CollectionOperationInterface.
4. Return null for missing items (API Platform emits a 404 automatically).
5. Wire on the operation: new Get(provider: MyProvider::class).

Guardrails

• Inject a repository or a service, never EntityManagerInterface directly inside a Provider.
• Do not code role checks inside the Provider — use security: on the operation or a voter.
• Do not persist from a Provider; that is the Processor's job.
• Remove any SerializerAwareProviderInterface / SerializableProvider implementation — those interfaces are deprecated since 4.2 and gone in 5.0.

Progressive disclosure

• SKILL.md covers the basic pattern and rules.
• reference.md carries the full decoration recipe, the collection-vs-item discriminator, a header-versioned example, and an N+1-avoidance reminder.

Output contract

• A new Provider class in src/State/ wired on the operation.
• Functional tests covering the happy path and the null/404 case.
• No legacy interfaces remaining; no hardcoded security inside the Provider.

References

• reference.md