<XR>(context: Context.Context<XR>): <A, E, R extends XR>(
self: Stream<A, E, R>
) => AsyncIterable<A>
<A, E, XR, R extends XR>(
self: Stream<A, E, R>,
context: Context.Context<XR>
): AsyncIterable<A>Converts the stream to an AsyncIterable using the provided services.
When to use
Use when converting outside an Effect and you already have the Context
needed to run the stream.
Example (Converting to an AsyncIterable with services)
import { Context, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const iterable = Stream.toAsyncIterableWith(stream, Context.empty())
const collect = async () => {
const results: Array<number> = []
for await (const value of iterable) {
results.push(value)
}
console.log(results)
}
collect()
// [ 1, 2, 3 ]destructors
Source effect/Stream.ts:1132245 lines
export const const toAsyncIterableWith: {
<XR>(context: Context.Context<XR>): <
A,
E,
R extends XR
>(
self: Stream<A, E, R>
) => AsyncIterable<A>
<A, E, XR, R extends XR>(
self: Stream<A, E, R>,
context: Context.Context<XR>
): AsyncIterable<A>
}
Converts the stream to an AsyncIterable using the provided services.
When to use
Use when converting outside an Effect and you already have the Context
needed to run the stream.
Example (Converting to an AsyncIterable with services)
import { Context, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const iterable = Stream.toAsyncIterableWith(stream, Context.empty())
const collect = async () => {
const results: Array<number> = []
for await (const value of iterable) {
results.push(value)
}
console.log(results)
}
collect()
// [ 1, 2, 3 ]
toAsyncIterableWith: {
<function (type parameter) XR in <XR>(context: Context.Context<XR>): <A, E, R extends XR>(self: Stream<A, E, R>) => AsyncIterable<A>XR>(context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <XR>(context: Context.Context<XR>): <A, E, R extends XR>(self: Stream<A, E, R>) => AsyncIterable<A>XR>): <function (type parameter) A in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>A, function (type parameter) E in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>E, function (type parameter) R in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>R extends function (type parameter) XR in <XR>(context: Context.Context<XR>): <A, E, R extends XR>(self: Stream<A, E, R>) => AsyncIterable<A>XR>(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 extends XR>(self: Stream<A, E, R>): AsyncIterable<A>A, function (type parameter) E in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>E, function (type parameter) R in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>R>) => interface AsyncIterable<T, TReturn = any, TNext = any>AsyncIterable<function (type parameter) A in <A, E, R extends XR>(self: Stream<A, E, R>): AsyncIterable<A>A>
<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>E, function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR, function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>R extends function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR>(
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, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>E, function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>R>,
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR>
): interface AsyncIterable<T, TReturn = any, TNext = any>AsyncIterable<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A>
} = dual<(...args: Array<any>) => any, <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>) => AsyncIterable<A>>(arity: 2, body: <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>) => AsyncIterable<A>): ((...args: Array<any>) => any) & (<A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>) => AsyncIterable<A>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(
2,
<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>E, function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR, function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>R extends function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR>(
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, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>E, function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>R>,
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>XR>
): interface AsyncIterable<T, TReturn = any, TNext = any>AsyncIterable<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A> => ({
[var Symbol: SymbolConstructorSymbol.SymbolConstructor.asyncIterator: typeof Symbol.asyncIteratorA method that returns the default async iterator for an object. Called by the semantics of
the for-await-of statement.
asyncIterator]() {
const const runPromise: (
effect: Effect<A, E, XR>,
options?: RunOptions | undefined
) => Promise<A>
import EffectEffect.const runPromiseWith: <R>(
context: Context.Context<R>
) => <A, E>(
effect: Effect<A, E, R>,
options?: RunOptions | undefined
) => Promise<A>
Executes an effect as a Promise with the provided services.
When to use
Use when you already have a Context and need Promise interop that rejects on
effect failure.
Example (Running with services as a promise)
import { Context, Effect } from "effect"
interface Config {
apiUrl: string
}
const Config = Context.Service<Config>("Config")
const context = Context.make(Config, {
apiUrl: "https://api.example.com"
})
const program = Effect.gen(function*() {
const config = yield* Config
return `Connecting to ${config.apiUrl}`
})
Effect.runPromiseWith(context)(program).then(console.log)
runPromiseWith(context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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;
}
const runPromiseExit: (
effect: Effect<A, E, XR>,
options?: RunOptions | undefined
) => Promise<Exit.Exit<A, E>>
import EffectEffect.const runPromiseExitWith: <R>(
context: Context.Context<R>
) => <A, E>(
effect: Effect<A, E, R>,
options?: RunOptions | undefined
) => Promise<Exit.Exit<A, E>>
Runs an effect and returns a Promise of Exit with provided services.
When to use
Use when you already have a Context and need Promise interop that preserves
success and failure as an Exit.
Example (Running with services as an Exit promise)
import { Context, Effect, Exit } from "effect"
interface Database {
query: (sql: string) => string
}
const Database = Context.Service<Database>("Database")
const services = Context.make(Database, {
query: (sql) => `Result for: ${sql}`
})
const program = Effect.gen(function*() {
const db = yield* Database
return db.query("SELECT * FROM users")
})
Effect.runPromiseExitWith(services)(program).then((exit) => {
if (Exit.isSuccess(exit)) {
console.log("Success:", exit.value)
}
})
runPromiseExitWith(context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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;
}
const scope: Scope.Closeableconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import ScopeScope.const makeUnsafe: (
finalizerStrategy?: "sequential" | "parallel"
) => Closeable
Creates a new Scope synchronously without wrapping it in an Effect.
This is useful when you need a scope immediately but should be used with caution
as it doesn't provide the same safety guarantees as the Effect-wrapped version.
When to use
Use when a scope must be allocated synchronously and the caller will close it
manually.
Example (Creating a scope synchronously)
import { Console, Effect, Exit, Scope } from "effect"
// Create a scope immediately
const scope = Scope.makeUnsafe("sequential")
// Use it in an Effect program
const program = Effect.gen(function*() {
yield* Scope.addFinalizer(scope, Console.log("Cleanup"))
yield* Scope.close(scope, Exit.void)
})
makeUnsafe()
let let pull:
| Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
R
>
| undefined
import PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A>, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>E, void, function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>R> | undefined
let let currentIter:
| Iterator<A, any, any>
| undefined
interface Iterator<T, TReturn = any, TNext = any>Iterator<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A> | undefined
return {
async AsyncIterator<A, any, any>.next(...[value]: [] | [any]): Promise<IteratorResult<A, any>>next(): interface Promise<T>Represents the completion of an asynchronous operation
Promise<type IteratorResult<T, TReturn = any> =
| IteratorYieldResult<T>
| IteratorReturnResult<TReturn>
function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>): AsyncIterable<A>A>> {
if (let currentIter:
| Iterator<A, any, any>
| undefined
const next: IteratorResult<A, any>next = let currentIter: Iterator<A, any, any>currentIter.Iterator<A, any, any>.next(...[value]: [] | [any]): IteratorResult<A, any>next()
if (!const next: IteratorResult<A, any>next.done?: boolean | undefineddone) return const next: IteratorYieldResult<A>next
let currentIter:
| Iterator<A, any, any>
| undefined
var undefinedundefined
}
let pull:
| Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
R
>
| undefined
const runPromise: (
effect: Effect<A, E, XR>,
options?: RunOptions | undefined
) => Promise<A>
import ChannelChannel.const toPullScoped: <
OutElem,
OutErr,
OutDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone, Env>,
never,
Env
>
Converts a channel to a Pull within an existing scope.
Example (Converting channels to scoped pulls)
import { Channel, Data, Effect, Scope } from "effect"
class ScopedPullError extends Data.TaggedError("ScopedPullError")<{
readonly reason: string
}> {}
// Create a channel
const numbersChannel = Channel.fromIterable([1, 2, 3])
// Convert to Pull with explicit scope
const scopedPullEffect = Effect.gen(function*() {
const scope = yield* Scope.make()
const pull = yield* Channel.toPullScoped(numbersChannel, scope)
return pull
})
toPullScoped(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<A, E, R>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<A, E, R>.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; <…;
}
const scope: Scope.Closeableconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
const exit: Exit.Exit<
readonly [A, ...A[]],
Cause.Done<void> | E
>
const runPromiseExit: (
effect: Effect<A, E, XR>,
options?: RunOptions | undefined
) => Promise<Exit.Exit<A, E>>
let pull:
| Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
R
>
| undefined
let pull: {
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 ExitExit.const isSuccess: <A, E>(
self: Exit<A, E>
) => self is Success<A, E>
Checks whether an Exit is a Success.
When to use
Use as a type guard to narrow Exit<A, E> to Success<A, E> and access the
value property.
Example (Narrowing to success)
import { Exit } from "effect"
const exit = Exit.succeed(42)
if (Exit.isSuccess(exit)) {
console.log(exit.value) // 42
}
isSuccess(const exit: Exit.Exit<
readonly [A, ...A[]],
Cause.Done<void> | E
>
let currentIter:
| Iterator<A, any, any>
| undefined
const exit: Exit.Success<
readonly [A, ...A[]],
Cause.Done<void> | E
>
const exit: {
_tag: "Success";
value: A;
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;
}
Success<readonly [A, ...A[]], Done<void> | E>.value: readonly [A, ...A[]](property) Success<readonly [A, ...A[]], Done<void> | E>.value: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
var Symbol: SymbolConstructorSymbol.SymbolConstructor.iterator: typeof Symbol.iteratorA method that returns the default iterator for an object. Called by the semantics of the
for-of statement.
iterator]()
return let currentIter: Iterator<A, any, any>currentIter.Iterator<A, any, any>.next(...[value]: [] | [any]): IteratorResult<A, any>next()
} else if (import PullPull.const isDoneCause: <E>(
cause: Cause.Cause<E>
) => boolean
Checks whether a Cause contains any done errors.
When to use
Use when you need to test whether a pull failure cause represents normal
completion and only need a boolean result.
isDoneCause(const exit: Exit.Failure<
readonly [A, ...A[]],
Cause.Done<void> | E
>
const exit: {
_tag: "Failure";
cause: Cause.Cause<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;
}
Failure<readonly [A, ...A[]], Done<void> | E>.cause: Cause.Cause<E>(property) Failure<readonly [A, ...A[]], Done<void> | E>.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;
}
IteratorReturnResult<TReturn>.done: truedone: true, IteratorReturnResult<any>.value: anyvalue: var undefinedundefined }
}
throw import CauseCause.const squash: <E>(
self: Cause<E>
) => unknown
Collapses a Cause into a single unknown value, picking the "most
important" failure in this order:
When to use
Use to collapse a structured cause to the single value that synchronous and
promise runners would throw.
Details
- First
Fail error (the E value)
- First
Die defect
- A generic
Error("All fibers interrupted without error") for interrupt-only causes
- A generic
Error("Empty cause") for empty
This is the function used by Effect.runPromise and Effect.runSync to
decide what to throw.
Gotchas
This function is lossy. Use
prettyErrors
or iterate cause.reasons
when you need all failures.
Example (Squashing a cause)
import { Cause } from "effect"
console.log(Cause.squash(Cause.fail("error"))) // "error"
console.log(Cause.squash(Cause.die("defect"))) // "defect"
squash(const exit: Exit.Failure<
readonly [A, ...A[]],
Cause.Done<void> | E
>
const exit: {
_tag: "Failure";
cause: Cause.Cause<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;
}
Failure<readonly [A, ...A[]], Done<void> | E>.cause: Cause.Cause<E>(property) Failure<readonly [A, ...A[]], Done<void> | E>.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;
}
AsyncIterator<A, any, any>.return?(value?: any): Promise<IteratorResult<A, any>>return(_: any_) {
return const runPromise: (
effect: Effect<A, E, XR>,
options?: RunOptions | undefined
) => Promise<A>
import EffectEffect.const as: {
<B>(value: B): <A, E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
value: B
): Effect<B, E, R>
}
import ScopeScope.const close: <A, E>(
self: Scope,
exit: Exit<A, E>
) => Effect<void>
Closes a scope and runs its registered finalizers.
When to use
Use to close a scope manually with a specific exit value.
Details
Finalizers run in the scope's configured order and receive the supplied
Exit.
Example (Running scope finalizers)
import { Console, Effect, Exit, Scope } from "effect"
const resourceManagement = Effect.gen(function*() {
const scope = yield* Scope.make("sequential")
// Add multiple finalizers
yield* Scope.addFinalizer(scope, Console.log("Close database connection"))
yield* Scope.addFinalizer(scope, Console.log("Close file handle"))
yield* Scope.addFinalizer(scope, Console.log("Release memory"))
// Do some work...
yield* Console.log("Performing operations...")
// Close scope - finalizers run in reverse order of registration
yield* Scope.close(scope, Exit.succeed("Success!"))
// Output: "Release memory", "Close file handle", "Close database connection"
})
close(const scope: Scope.Closeableconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import ExitExit.const void: Exit.Exit<void, never>Provides a pre-allocated successful Exit with a void value.
When to use
Use when you need a shared successful Exit with no meaningful value.
Details
Equivalent to Exit.succeed(undefined) but shared as a single instance,
avoiding allocation for a common case.
Example (Referencing the void Exit)
import { Exit } from "effect"
const exit = Exit.void
console.log(Exit.isSuccess(exit)) // true
void),
{ done: truedone: true, value: undefinedvalue: var undefinedundefined }
))
}
}
}
})
)Referenced by 2 symbols