/interfaces-and-autowiring

name: interfaces-and-autowiring
description: "Master Symfony Dependency Injection with autowiring, #[Target] interface binding, decoration, and tagged services"
capabilities: [read, search]
tags: [architecture]
# projected by `bun run build` — do not edit by hand
allowed-tools:
  - Read
  - Glob
  - Grep

Interfaces And Autowiring (Symfony)

Use when

• A service depends on a concrete class and must be swappable or replaced in tests.
• Several implementations of one interface exist and the right one must be injected.
• Adding cross-cutting behavior (logging, caching, retries) around an existing service.
• Injecting scalars, parameters, env vars, or every service carrying a tag.
• Autowiring fails with "cannot autowire" or an ambiguous type.

Default workflow

1. Extract a focused interface for what the consumer actually needs. 2. Let autowiring bind it when there is a single implementation. 3. With several implementations, pick one per consumer through a named alias and `#[Target]`. 4. Add behavior around a service with `#[AsDecorator]` instead of editing or extending it. 5. Inject scalars with `#[Autowire]` and tagged collections with `#[AutowireIterator]`. 6. Confirm the result with `debug:autowiring` for each type involved.

Guardrails

• Constructor injection with `private readonly` dependencies; no setter injection, no container access.
• Keep interfaces small: one consumer need per interface.
• Make services `final` by default and decorate them rather than extend them.
• Use lazy services or service closures only for expensive dependencies that some paths skip.

Progressive disclosure

• Use this file for execution posture and risk controls.
• Open references when deep implementation details are needed.

Output contract

• Interfaces and the bindings or aliases that select each implementation.
• Decorators or tagged collections, with their priority.
• The `debug:autowiring` output for the types involved.

References

• `reference.md`