Resource Management (Scope)

Resource Management (Scope)

Acquire/​Release

const withConn = Effect.acquireRelease(
  Effect.sync(() => open()),
  (conn) => Effect.sync(() => close(conn))
).pipe(Effect.flatMap(use))

Scoped

yield* Effect.scoped(
  Effect.gen(function* () {
    const h = yield* Effect.acquireRelease(acquire(), release)
    return yield* use(h)
  })
)

Finalizers

yield* Effect.addFinalizer(() => cleanup)

Ensuring

operation.pipe(Effect.ensuring(cleanup))

Real-world snippet: wrap Promise APIs with typed errors and spans

const wrapS3Promise = <T>(promise: Promise<T> | Effect.Effect<Promise<T>>) =>
  Effect.gen(function* () {
    if (promise instanceof Promise) {
      return yield* Effect.tryPromise({ try: () => promise, catch: (cause) => new S3Error({ cause }) })
    }
    return yield* promise.pipe(
      Effect.flatMap((cb) =>
        Effect.tryPromise({ try: () => cb, catch: (cause) => new S3Error({ cause }) })
      )
    )
  }).pipe(Effect.catchTag("UnknownException", (cause) => new S3Error({ cause })))

// Usage with spans
const put = wrapS3Promise(client.send(new S3.PutObjectCommand(args))).pipe(
  Effect.withSpan("S3.putObject", { attributes: { key: args.Key } })
)

Local Source Reference

CRITICAL: Search local Effect source before implementing

The full Effect source code is available at docs/​effect-source/. Always search the actual implementation before writing Effect code.

Key Source Files

• Effect: docs/​effect-source/​effect/​src/​Effect.ts
• Scope: docs/​effect-source/​effect/​src/​Scope.ts

Example Searches

# Find acquireRelease patterns
grep -F "acquireRelease" docs/​effect-source/​effect/​src/​Effect.ts

# Study scoped operations
grep -F "scoped" docs/​effect-source/​effect/​src/​Effect.ts
grep -F "addFinalizer" docs/​effect-source/​effect/​src/​Effect.ts

# Find ensuring patterns
grep -F "ensuring" docs/​effect-source/​effect/​src/​Effect.ts

# Look at Scope implementation
grep -F "export" docs/​effect-source/​effect/​src/​Scope.ts | grep -F "function"

Workflow

1. Identify the resource management API you need (e.g., acquireRelease)
2. Search docs/​effect-source/​effect/​src/​Effect.ts for the implementation
3. Study the types and resource patterns
4. Look at test files for usage examples
5. Write your code based on real implementations

Real source code > documentation > assumptions

References

• Agent Skills overview: https://www.anthropic.com/news/skills
• Skills guide: https://docs.claude.com/en/docs/claude-code/skills