effect-io-ai

Package: effect
Module: Effect

Effect.mapError

Transforms or modifies the error produced by an effect without affecting its success value.

When to Use

This function is helpful when you want to enhance the error with additional information, change the error type, or apply custom error handling while keeping the original behavior of the effect’s success values intact. It only operates on the error channel and leaves the success channel unchanged.

Example

import { Effect } from "effect"

//      ┌─── Effect<number, string, never>
//      ▼
const simulatedTask = Effect.fail("Oh no!").pipe(Effect.as(1))

//      ┌─── Effect<number, Error, never>
//      ▼
const mapped = Effect.mapError(
  simulatedTask,
  (message) => new Error(message)
)

See

• map for a version that operates on the success channel.
• mapBoth for a version that operates on both channels.
• orElseFail if you want to replace the error with a new one.

Signature

declare const mapError: { <E, E2>(f: (e: E) => E2): <A, R>(self: Effect<A, E, R>) => Effect<A, E2, R>; <A, E, R, E2>(self: Effect<A, E, R>, f: (e: E) => E2): Effect<A, E2, R>; }

Source

Since v2.0.0