<E, X, R2>(
cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>
): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>
<A, E, R, X, R2>(
self: Stream<A, E, R>,
cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>
): Stream<A, E, R | R2>Runs the provided effect when the stream fails, passing the failure cause.
Gotchas
Note: Unlike Effect.onError there is no guarantee that the provided
effect will not be interrupted.
Example (Running an effect on errors)
import { Cause, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.make(1, 2, 3).pipe(
Stream.concat(Stream.fail("boom")),
Stream.onError((cause) => Console.log(`Stream failed: ${Cause.squash(cause)}`))
)
yield* Stream.runCollect(stream)
})
Effect.runPromiseExit(program)
// Output:
// Stream failed: boomerror handling
Source effect/Stream.ts:984012 lines
export const const onError: {
<E, X, R2>(
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>
): <A, R>(
self: Stream<A, E, R>
) => Stream<A, E, R2 | R>
<A, E, R, X, R2>(
self: Stream<A, E, R>,
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>
): Stream<A, E, R | R2>
}
Runs the provided effect when the stream fails, passing the failure cause.
Gotchas
Note: Unlike Effect.onError there is no guarantee that the provided
effect will not be interrupted.
Example (Running an effect on errors)
import { Cause, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.make(1, 2, 3).pipe(
Stream.concat(Stream.fail("boom")),
Stream.onError((cause) => Console.log(`Stream failed: ${Cause.squash(cause)}`))
)
yield* Stream.runCollect(stream)
})
Effect.runPromiseExit(program)
// Output:
// Stream failed: boom
onError: {
<function (type parameter) E in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>E, function (type parameter) X in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>X, function (type parameter) R2 in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>R2>(
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>
cause: Cause.Cause<E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<function (type parameter) E in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>E>) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) X in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>X, never, function (type parameter) R2 in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>R2>
): <function (type parameter) A in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>A, function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>R>(self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>A, function (type parameter) E in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>E, function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>R>) => interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>A, function (type parameter) E in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>E, function (type parameter) R2 in <E, X, R2>(cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): <A, R>(self: Stream<A, E, R>) => Stream<A, E, R2 | R>R2 | function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A, E, R2 | R>R>
<function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R, function (type parameter) X in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>X, function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R>,
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>
cause: Cause.Cause<E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E>) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) X in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>X, never, function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2>
): interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R | function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2>
} = import dualdual(2, <function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R, function (type parameter) X in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>X, function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R>,
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>
cause: Cause.Cause<E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E>) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) X in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>X, never, function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2>
): interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>A, function (type parameter) E in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>E, function (type parameter) R in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R | function (type parameter) R2 in <A, E, R, X, R2>(self: Stream<A, E, R>, cleanup: (cause: Cause.Cause<E>) => Effect.Effect<X, never, R2>): Stream<A, E, R | R2>R2> => const fromChannel: <
Arr extends Arr.NonEmptyReadonlyArray<any>,
E,
R
>(
channel: Channel.Channel<
Arr,
E,
void,
unknown,
unknown,
unknown,
R
>
) => Stream<
Arr extends Arr.NonEmptyReadonlyArray<infer A>
? A
: never,
E,
R
>
Creates a stream from a array-emitting Channel.
Example (Creating a stream from an array-emitting channel)
import { Channel, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const channel = Channel.succeed([1, 2, 3] as const)
const stream = Stream.fromChannel(channel)
const result = yield* Stream.runCollect(stream)
yield* Console.log(result)
})
// Output: [ 1, 2, 3 ]
fromChannel(import ChannelChannel.onError(self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Stream<out A, out E = never, out R = never>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<out A, out E = never, out R = never>.channel: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
cleanup: (
cause: Cause.Cause<E>
) => Effect.Effect<X, never, R2>