effect-facet-sink-reducing

name	effect-facet-sink-reducing
description	Guidance for facet `effect/Sink#reducing` focused on APIs like map, fail, and make. Load after `effect-skill-router` when this facet is the primary owner.

Effect Facet Sink#reducing

Owned scope

• Owns only effect/Sink#reducing.
• Parent module: effect/Sink.

What it is for

• reduce/fold aggregation behavior. Module-specific APIs and usage patterns for Effect programs.

API quick reference

• map
• fail
• make
• mapEnd
• flatMap
• succeed
• failSync
• mapError
• mapInput
• failCause
• fromQueue
• mapEffect
• fromEffect
• fromPubSub
• fromChannel
• mapLeftover
• mapEffectEnd
• failCauseSync
• Full API list: references/api-reference.md

How to use it

• Keep work focused on the reducing concern for effect/Sink.
• Start with constructor-style APIs to build values/services before composing operations.
• Prefer pipe-based composition to keep transformations explicit and testable.
• Treat stateful APIs as synchronization boundaries and keep updates atomic.
• Keep runtime/execute APIs at edges; compose pure transformations before execution.

Starter example

import { Effect } from "effect";
import * as Sink from "effect/Sink";
import * as Stream from "effect/Stream";

// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42);

// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3);
const program = Stream.run(stream, sink);

Effect.runPromise(program).then(console.log);
// Output: 42

Common pitfalls

• Prefer explicit, typed combinators over ad-hoc casting or unchecked assumptions.

Not covered here

• Sibling facets under the same parent are out of scope:
  • effect-facet-sink-core (effect/Sink#core)
  • effect-facet-sink-transforms (effect/Sink#transforms)
• Parent module ownership belongs to effect-module-sink.

Escalate to

• effect-module-sink for parent module-wide workflows.
• effect-skill-router for cross-module routing and ownership checks.

Reference anchors

• Parent tests: packages/effect/test/Sink.test.ts
• Parent tests: packages/effect/test/unstable/process/ChildProcess.test.ts
• API details: references/api-reference.md
• Usage notes: references/usage-reference.md
• Ownership mapping: references/owner.md