/strategy-pattern

name: strategy-pattern
description: Implement the Strategy pattern with Symfony's tagged services for runtime algorithm selection and extensibility
capabilities: [read, search]
tags: [architecture]
# projected by `bun run build` — do not edit by hand
allowed-tools:
  - Read
  - Glob
  - Grep

Strategy Pattern (Symfony)

Use when

• One operation has several interchangeable algorithms chosen at runtime, such as payment providers or export formats.
• A `switch` or `match` on a type string keeps growing.
• New variants must be added without editing the code that selects them.

Default workflow

1. Define the strategy interface, with a `supports()` method or a key per strategy. 2. Tag every implementation through `#[AutoconfigureTag]` on the interface or on each class. 3. Inject them with `#[AutowireIterator]` to try each in order, or `#[AutowireLocator]` to fetch one by key. 4. Set priorities where evaluation order matters, and register a fallback strategy. 5. Test each strategy alone, and the selector with fakes.

Guardrails

• The selector fails explicitly when no strategy supports the input.
• Keep strategies stateless and independent of each other.
• Two cases that will not grow do not need the pattern: a `match` is enough.

Progressive disclosure

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

Output contract

• The interface and its tagged implementations.
• The selector, with its order and its fallback.
• Tests per strategy and for the no-match case.

References

• `reference.md`