effect-ts_skill

Overview

This skill provides practical, expert guidance for working with Effect-TS (the Effect library) in TypeScript projects. It helps with patterns for error handling, services and layers, dependency injection, resource management, concurrency, and integrating Effect with frameworks like Next.js via @prb/effect-next. Use it when writing, refactoring, or debugging code that imports from 'effect'.

How this skill works

The skill inspects code for existing Effect usage and recommends consistent, idiomatic patterns. It checks for service and layer patterns, error taxonomy, and testing approaches, and it advises when to consult the local Effect source at ~/.effect for deep type or runtime issues. For integration scenarios (including Effect + Next.js), it suggests concrete layering and lifecycle patterns and safety checks for resource management and concurrency.

When to use it

• Implementing or refactoring Services and Layers or adding new dependencies
• Designing typed error models and handling multiple error classes
• Converting imperative async code (promises/try-catch) to Effect patterns
• Managing resources, scoped lifetimes, or complex concurrency
• Integrating Effect with Next.js using @prb/effect-next or other adapters

Best practices

• Check the codebase first for existing Effect patterns and follow them for consistency
• Use typed errors (Data.TaggedError) and Effect.fail/catchTag rather than throw/catch
• Prefer Context.Tag / Effect.Service + Layer compositions for dependency injection
• Use Effect.gen or Effect.fn for readable sequential logic and better stack traces
• Manage resources with acquireUseRelease / scoped effects and avoid unsafe APIs (e.g., unsafeMake)

Example use cases

• Create a Database service as a Layer and inject it into handlers via Effect.provide
• Refactor a Promise-based API call into Effect.tryPromise with typed errors and retry Schedule
• Implement request-scoped resources in Next.js using @prb/effect-next and scoped layers
• Write tests that provide test-specific Layers and use Effect.result to assert failures and successes
• Handle cancellation and interruptions separately from domain errors using catchTag and onInterrupt