effect-io-ai

Package: effect
Module: Stream

Stream.catchIf

Recovers from errors that match a predicate by switching to a recovery stream.

Details

When a failure matches the filter, the stream switches to the recovery stream. Non-matching failures propagate downstream, so the error type is preserved unless the filter narrows it.

Example (Catching matching failures)

import { Console, Effect, Stream } from "effect"

const stream = Stream.make(1, 2).pipe(
  Stream.concat(Stream.fail(42)),
  Stream.catchIf(
    (error): error is 42 => error === 42,
    () => Stream.make(999)
  )
)

const program = Effect.gen(function*() {
  const values = yield* Stream.runCollect(stream)
  yield* Console.log(values)
  // Output: [ 1, 2, 999 ]
})

Effect.runPromise(program)

Signature

declare const catchIf: { <E, EB extends E, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(refinement: Refinement<NoInfer<E>, EB>, f: (e: EB) => Stream<A2, E2, R2>, orElse?: ((e: Exclude<E, EB>) => Stream<A3, E3, R3>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A2 | Exclude<A3, unassigned>, E2 | E3 | (A3 extends unassigned ? Exclude<E, EB> : never), R | R2 | R3>; <E, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(predicate: Predicate<NoInfer<E>>, f: (e: NoInfer<E>) => Stream<A2, E2, R2>, orElse?: ((e: NoInfer<E>) => Stream<A3, E3, R3>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A2 | Exclude<A3, unassigned>, E2 | E3 | (A3 extends unassigned ? E : never), R | R2 | R3>; <A, E, R, EB extends E, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(self: Stream<A, E, R>, refinement: Refinement<E, EB>, f: (e: EB) => Stream<A2, E2, R2>, orElse?: ((e: Exclude<E, EB>) => Stream<A3, E3, R3>) | undefined): Stream<A | A2 | Exclude<A3, unassigned>, E2 | E3 | (A3 extends unassigned ? Exclude<E, EB> : never), R | R2 | R3>; <A, E, R, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(self: Stream<A, E, R>, predicate: Predicate<E>, f: (e: E) => Stream<A2, E2, R2>, orElse?: ((e: E) => Stream<A3, E3, R3>) | undefined): Stream<A | A2 | Exclude<A3, unassigned>, E2 | E3 | (A3 extends unassigned ? E : never), R | R2 | R3>; }

Source

Since v4.0.0