Search documentation

Search by topic, API name, or import path.

GitHub ↗

variable / @typed/fx

Fx.filterMapLoopCause

Loops over the failure causes of an Fx with an accumulator, potentially transforming or filtering them. This allows for complex error handling logic that maintains state across failures.

Package version
2.0.0-beta.7
Category
Stateful transforms
Since
1.0.0
Member of
Fx

Follow one execution

Loops over the failure causes of an Fx with an accumulator, potentially transforming or filtering them. This allows for complex error handling logic that maintains state across failures.

Fx timelinefilterMapLoopCause can suppress a terminal causefilterMapLoopCause
OperatorfilterMapLoopCause(0, suppress)
Read this diagram

Follow each lane from left to right. Events stacked vertically share a tick; the green cursor marks the current time across every lane.

  • A value
    The text inside the pill is the emitted value.
  • Work starts
    The raised chevron starts an inner run (^ in the source).
  • The run returns
    The vertical bar ends this lane’s run.
  • A cause is delivered
    The exclamation mark belongs to this lane.
  • Work is interrupted
    The cross marks cancellation of this run.
  • Current time
    The line and diamond move together across all lanes.
  • Happening now
    A highlighted event is at the current tick.
  • Still ahead
    Muted, dashed values have not happened yet.
  • Time continues
    The lane’s arrow is not a return marker. An empty stretch can be quiet work that is still running.

Illustrated ticks start at 0. At 1×, one illustrated tick takes one second; captions specify real durations when timing matters. A cause or interruption belongs to its lane, and other work may continue. Scroll horizontally to inspect the rest of a long timeline.

Failure state is isolated to one run and discarded afterward. The pure callback acquires no resources; defects and interrupts are visible inside the full Cause supplied to it.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

import { Fx } from "@typed/fx";

Access Fx.filterMapLoopCause through the imported Fx export. Its declaration below describes the member.

This public exposure is a re-export. Its import path is supported; declaration documentation is shared with the other public exposures below.

Signatures

export declare const filterMapLoopCause: {
    <B, A, C>(seed: B, f: (acc: B, a: Cause.Cause<A>) => readonly [
        Option.Option<Cause.Cause<C>>,
        B
    ]): <E, R>(self: Fx<A, E, R>) => Fx<A, C, R>;
    <A, E, R, B, C>(self: Fx<A, E, R>, seed: B, f: (acc: B, a: Cause.Cause<E>) => readonly [
        Option.Option<Cause.Cause<C>>,
        B
    ]): Fx<A, C, R>;
};

Why

filterMapLoopCause transforms, suppresses, or reclassifies successive failure causes with explicit state. Successful values pass through; each observed cause advances the accumulator and None suppresses forwarding that cause.

Ownership and lifetime

Failure state is isolated to one run and discarded afterward. The pure callback acquires no resources; defects and interrupts are visible inside the full Cause supplied to it.

Examples

import { Cause, Option } from "effect"
import { Fx } from "@typed/fx"

const firstFailureOnly = Fx.fail("offline").pipe(
  Fx.filterMapLoopCause(false, (seen, cause) => [seen ? Option.none() : Option.some(Cause.map(cause, String)), true]),
)

Other public imports

These import paths expose the same declaration. Each page retains its own public name and signature.

Source