Effect-TS Best Practices

Opinionated patterns for Effect-TS codebases. Effect provides typed functional programming with composable errors, dependency injection, and observability.

Critical Rules

1. NEVER use any or type casts (as Type) - Use Schema.make() for branded types, Schema.decodeUnknown() for parsing
2. Don't use catchAll when error type is never - No errors to catch
3. Never use global Error in Effect channels - Use Schema.TaggedError for domain errors
4. Ban { disableValidation: true } - Lint against this
5. Don't wrap safe operations in Effect - Only use Effect.try() for throwing operations
6. Use mapError not catchAllCause - Distinguish expected errors from bugs
7. Never silently swallow errors - Failures MUST be visible in the Effect's error channel E

Quick Reference