By name: effect-ts-anti-patterns description: Detect v3 API usage, Promise-first code, hidden service dependencies, oversized Effect.gen blocks, module-level singletons, import path violations, TypeScript safety violations, incorrect service definitions. Effect-TS v4.
v4 API Detection (must flag)
| v3 Pattern (FLAG) | v4 Replacement |
|---|---|
catchAll |
catch |
catchAllCause |
catchCause |
catchAllDefect |
catchDefect |
catchSome |
catchFilter |
catchSomeCause |
catchCauseFilter |
catchSomeDefect |
DELETED |
either |
result |
fork |
forkChild |
forkDaemon |
forkDetach |
forkAll |
Effect.forEach with forkChild |
forkWithErrorHandler |
DELETED |
FiberRef |
Context.Reference (in References module) |
Runtime<R> / Runtime.runFork(runtime) |
Effect.services<R>() / Effect.runForkWith(services) |
Effect.Do + Effect.bind |
Effect.gen |
Context.Tag / Effect.Tag |
Context.Service class: class Svc extends Context.Service<Svc, Shape>()("Svc") {} |
Schema.Schema.Type<typeof S> |
Schema.Type<typeof S> |
Schema.decodeUnknown / Schema.decode |
Schema.decodeUnknownEffect / Schema.decodeEffect |
new Schema.ArbitraryCompiler() |
Schema.makeArbitrary(S) |
Schema.Codec.ToAsserts |
Schema.asserts(schema, input) |
@effect/platform for HTTP/SQL/RPC/Schema |
effect/unstable/* |
Structural Detection
| Anti-pattern | Detect | Impact | Severity |
|---|---|---|---|
| Promise-first code | await / .then() / new Promise inside Effect.gen without Effect interop |
Uncontrolled computation — bypasses concurrency, error tracking, interruption | HIGH |
| Hidden service deps | Concrete types (drivers, clients, config objects) in Requirements instead of Context tags |
Brittle coupling — untestable, unswappable | HIGH |
| Oversized Effect.gen | Single block mixing validation + fetch + transform + persist + log | Untestable phases, impossible error-path reasoning | MEDIUM |
| Module-level singleton | const client = new Pool() at module scope, not inside Layer |
No release path, no test substitution, invisible lifetime | HIGH |
| Misaligned imports | Non-canonical, internal, or platform-specific subpaths | Unstable API surface — can break on minor version | HIGH |
| TypeScript safety violations | any, as casts erasing Effect's A/E/R channels |
Disables all 3 compiler verifications simultaneously | HIGH |
| Bad service definition | Tag without shape interface, or tag+impl same class | Consumers can't see operations; can't substitute implementations | MEDIUM |
Effect.Do usage |
v3-only pattern deleted in v4 | Won't compile | HIGH |
| Tacit function refs | Effect.map(fn) instead of Effect.map((x) => fn(x)) |
Erases generics, breaks inference, unclear stack traces | MEDIUM |
| Wall-clock time | Date.now() / new Date() instead of Clock |
Breaks referential transparency, testability, determinism | HIGH |
DO NOT detect here — delegate
| Concern | Delegate to |
|---|---|
| Concurrency (forkChild, Semaphore, Queue) | effect-ts-concurrency |
| Typed errors, catch, retry, recovery | effect-ts-error-handling |
Resource lifecycle, Scope, acquireRelease |
effect-ts-resource-layer |
| Mental model violations (mid-flight execution, per-request provisioning) | effect-ts-principle-thinking |
Severity
| Level | Criteria |
|---|---|
| HIGH | Direct type unsafety, runtime resource leaks, prevents testable substitution, v3 API that won't compile |
| MEDIUM | Structural degradation — hurts clarity, testability, maintainability |
| LOW | Non-idiomatic but functionally correct |
Output per finding
- File:line location
- Anti-pattern name (from table above)
- Delegation target skill for fix
- Risk level (HIGH/MEDIUM/LOW)
Guardrails
- Detect structural patterns only. Never diagnose runtime behavior.
- Never suggest implementation changes — flag and delegate to the fix skill.
- Per finding, specify which skill handles the fix.
- Focus on timeless structural principles, not version-specific APIs except v3→v4 migration.
- v4 beta APIs shift between releases — verify existence in
packages/effect/src/*.tsbefore including in findings.