no-inline-schema-codec

Intent: a decoder or encoder is a named module-level constant, not built and applied inline.

// ❌ no
const toPayment = (raw: unknown) => Schema.decodeUnknownSync(PaymentResponse)(raw)

// ✅ yes
const decodePaymentResponse = Schema.decodeUnknownSync(PaymentResponse)

const toPayment = (raw: unknown) => decodePaymentResponse(raw)

Trigger: an immediate application Schema.decode*(X)(input) or Schema.encode*(X)(input) (the Effect, Exit, Option, Promise, Result and Sync variants, Unknown included) inside a function, test callbacks included.

Exemptions and blind spots: module scope, and the generator of Layer.effect(T, Effect.gen(…)) or Layer.effect(T)(Effect.gen(…)) (also Layer.scoped), which run once; functions nested in that generator, such as the service methods, are checked. Codecs built inside a function and applied later (const decode = Schema.decodeUnknownEffect(X)), codecs passed as callbacks (Effect.flatMap(Schema.decodeUnknownEffect(X))) and a Layer built through .pipe(Layer.effect(T)) slip through. Whether the codec should be synchronous is not this rule’s concern: see schema-sync (effecttsgo).

Why: a named codec says what it decodes at the call site and is built once, instead of at every call.

Options: none

Fix: none