<E, X, E2, R2>(
f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>
): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>
<A, E, R, X, E2, R2>(
self: Effect<A, E, R>,
f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>
): Effect<A, E | E2, R | R2>Runs an effectful operation with the full Cause when the source effect
fails.
When to use
Use when failure observation needs typed failures, defects, and interruptions rather than only the typed error value.
Details
Use this to log or inspect typed failures, defects, and interruptions. When the operation succeeds, the original cause is preserved. If the operation fails, its error is also represented in the returned effect.
Example (Observing full failure causes)
import { Cause, Console, Effect } from "effect"
const task = Effect.fail("Something went wrong")
const program = Effect.tapCause(
task,
(cause) => Console.log(`Logging cause: ${Cause.squash(cause)}`)
)
Effect.runPromiseExit(program).then(console.log)
// Output: "Logging cause: Error: Something went wrong"
// Then: { _id: 'Exit', _tag: 'Failure', cause: ... }export const const tapCause: {
<E, X, E2, R2>(
f: (
cause: Cause.Cause<NoInfer<E>>
) => Effect<X, E2, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A, E | E2, R2 | R>
<A, E, R, X, E2, R2>(
self: Effect<A, E, R>,
f: (
cause: Cause.Cause<E>
) => Effect<X, E2, R2>
): Effect<A, E | E2, R | R2>
}
Runs an effectful operation with the full Cause when the source effect
fails.
When to use
Use when failure observation needs typed failures, defects, and interruptions
rather than only the typed error value.
Details
Use this to log or inspect typed failures, defects, and interruptions. When
the operation succeeds, the original cause is preserved. If the operation
fails, its error is also represented in the returned effect.
Example (Observing full failure causes)
import { Cause, Console, Effect } from "effect"
const task = Effect.fail("Something went wrong")
const program = Effect.tapCause(
task,
(cause) => Console.log(`Logging cause: ${Cause.squash(cause)}`)
)
Effect.runPromiseExit(program).then(console.log)
// Output: "Logging cause: Error: Something went wrong"
// Then: { _id: 'Exit', _tag: 'Failure', cause: ... }
tapCause: {
<function (type parameter) E in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E, function (type parameter) X in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>X, function (type parameter) E2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E2, function (type parameter) R2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>R2>(
f: (
cause: Cause.Cause<NoInfer<E>>
) => Effect<X, E2, R2>
cause: Cause.Cause<NoInfer<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.interface Cause<out E>A structured representation of how an Effect failed.
When to use
Use to preserve the full structured failure information for an effect instead
of collapsing it to a single error value.
Details
Access the individual failure entries through the reasons array, then
narrow each entry with
isFailReason
,
isDieReason
, or
- Use
hasFails
/
hasDies
/
hasInterrupts
to test
for the presence of specific reason kinds without iterating.
- Use
findError
/
findDefect
to extract the first value
of a given kind.
- Use
combine
to merge two causes.
Cause implements Equal — two causes with the same reasons (by value)
compare as equal.
Example (Creating and inspecting a cause)
import { Cause } from "effect"
const cause = Cause.fail("Something went wrong")
console.log(cause.reasons.length) // 1
console.log(Cause.isFailReason(cause.reasons[0])) // true
Companion namespace for the Cause interface.
Cause<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) E in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E>>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>X, function (type parameter) E2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E2, function (type parameter) R2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>R2>
): <function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>A, function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>R>(self: Effect<A, E, R>(parameter) self: {
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;
}
interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>A, function (type parameter) E in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E, function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>R>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>A, function (type parameter) E in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E | function (type parameter) E2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>E2, function (type parameter) R2 in <E, X, E2, R2>(f: (cause: Cause.Cause<NoInfer<E>>) => Effect<X, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A, E | E2, R2 | R>R2 | function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A, E | E2, R2 | R>R>
<function (type parameter) A in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R, function (type parameter) X in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R2>(
self: Effect<A, E, R>(parameter) self: {
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;
}
interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R>,
f: (
cause: Cause.Cause<E>
) => Effect<X, E2, 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.interface Cause<out E>A structured representation of how an Effect failed.
When to use
Use to preserve the full structured failure information for an effect instead
of collapsing it to a single error value.
Details
Access the individual failure entries through the reasons array, then
narrow each entry with
isFailReason
,
isDieReason
, or
- Use
hasFails
/
hasDies
/
hasInterrupts
to test
for the presence of specific reason kinds without iterating.
- Use
findError
/
findDefect
to extract the first value
of a given kind.
- Use
combine
to merge two causes.
Cause implements Equal — two causes with the same reasons (by value)
compare as equal.
Example (Creating and inspecting a cause)
import { Cause } from "effect"
const cause = Cause.fail("Something went wrong")
console.log(cause.reasons.length) // 1
console.log(Cause.isFailReason(cause.reasons[0])) // true
Companion namespace for the Cause interface.
Cause<function (type parameter) E in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R2>
): interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Effect<A, E, R>, f: (cause: Cause.Cause<E>) => Effect<X, E2, R2>): Effect<A, E | E2, R | R2>R2>
} = import internalinternal.const tapCause: {
<E, B, E2, R2>(
f: (
cause: NoInfer<Cause.Cause<E>>
) => Effect.Effect<B, E2, R2>
): <A, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: (
cause: NoInfer<Cause.Cause<E>>
) => Effect.Effect<B, E2, R2>
): Effect.Effect<A, E | E2, R | R2>
}