<E>(self: Cause<E>): Result.Result<E, Cause<never>>Returns a Result whose success value is the first typed error value E
from a Fail reason in the cause. If the cause has no Fail reason,
the failure value is the original cause narrowed to Cause<never>, because
it contains no typed error reasons.
When to use
Use when you need the first typed error value from a Cause as a Result
that preserves the original cause when no match is found.
Example (Extracting the first error value)
import { Cause, Result } from "effect"
const result = Cause.findError(Cause.fail("error"))
if (!Result.isFailure(result)) {
console.log(result.success) // "error"
}export const const findError: <E>(
self: Cause<E>
) => Result.Result<E, Cause<never>>
Returns a Result whose success value is the first typed error value E
from a Fail reason in the cause. If the cause has no Fail reason,
the failure value is the original cause narrowed to Cause<never>, because
it contains no typed error reasons.
When to use
Use when you need the first typed error value from a Cause as a Result
that preserves the original cause when no match is found.
Example (Extracting the first error value)
import { Cause, Result } from "effect"
const result = Cause.findError(Cause.fail("error"))
if (!Result.isFailure(result)) {
console.log(result.success) // "error"
}
findError: <function (type parameter) E in <E>(self: Cause<E>): Result.Result<E, Cause<never>>E>(self: Cause<E>(parameter) self: {
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;
}
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 <E>(self: Cause<E>): Result.Result<E, Cause<never>>E>) => import ResultResult.type Result<A, E = never> = Result.Success<A, E> | Result.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) E in <E>(self: Cause<E>): Result.Result<E, Cause<never>>E, 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<never>> = import effecteffect.const findError: <E>(
self: Cause.Cause<E>
) => Result.Result<E, Cause.Cause<never>>