effect-facet-channel-composition

name	effect-facet-channel-composition
description	Guidance for facet `effect/Channel#composition` focused on APIs like map, flatMap, and mapDone. Load after `effect-skill-router` when this facet is the primary owner.

Effect Facet Channel#composition

Owned scope

• Owns only effect/Channel#composition.
• Parent module: effect/Channel.

What it is for

• sequencing/transformation pipelines. The Channel module provides a powerful abstraction for bi-directional communication and streaming operations. A Channel is a nexus of I/O operations that supports both reading and writing, forming the foundation for Effect's Stream and Sink abstractions.

API quick reference

• map
• flatMap
• mapDone
• provide
• mapAccum
• mapError
• mapInput
• mapEffect
• mapDoneEffect
• mapInputError
• provideService
• provideServiceEffect
• provideContext
• bind
• merge
• bindTo
• concat
• pipeTo
• Full API list: references/api-reference.md

How to use it

• Keep work focused on the composition concern for effect/Channel.
• Prefer pipe-based composition to keep transformations explicit and testable.
• Use the reference docs to select the smallest API surface that solves your task.
• Validate behavior against existing tests before introducing new usage patterns.

Starter example

import { Channel } from "effect";

// Simple channel that outputs numbers
const numberChannel = Channel.succeed(42);

// Transform channel that doubles values
const doubleChannel = Channel.map(numberChannel, (n) => n * 2);

// Running the channel would output: 84

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-channel-core (effect/Channel#core)
  • effect-facet-channel-utilities (effect/Channel#utilities)
• Parent module ownership belongs to effect-module-channel.

Escalate to

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

Reference anchors

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