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catchCauseIf

Recovers a failure cause only when a predicate accepts the complete cause.

Package version
2.0.0-beta.7
Category
Errors and recovery
Since
1.0.0

Follow one execution

Recovers a failure cause only when a predicate accepts the complete cause.

Fx timelinecatchCauseIf recovers only when its Cause predicate matchescatchCauseIf
OperatorcatchCauseIf(hasDies, fallback)
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.

The predicate receives the source cause unchanged. A match starts one lazy fallback in the same subscription; otherwise the original cause propagates. The fallback’s requirements and errors are added, prior source values stay delivered, and interrupting the returned Fx interrupts its active run.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const catchCauseIf: {
    <E, A2, E2, R2>(predicate: (cause: Cause.Cause<E>) => boolean, f: (cause: Cause.Cause<E>) => Fx<A2, E2, R2>): <A, R>(self: Fx<A, E, R>) => Fx<A | A2, E | E2, R | R2>;
    <A, E, R, A2, E2, R2>(self: Fx<A, E, R>, predicate: (cause: Cause.Cause<E>) => boolean, f: (cause: Cause.Cause<E>) => Fx<A2, E2, R2>): Fx<A | A2, E | E2, R | R2>;
};

Why

Cause-level predicates can distinguish defects, interruption, sequential or parallel cause structure that a typed-error predicate cannot observe.

Ownership and lifetime

The predicate receives the source cause unchanged. A match starts one lazy fallback in the same subscription; otherwise the original cause propagates. The fallback’s requirements and errors are added, prior source values stay delivered, and interrupting the returned Fx interrupts its active run.

Examples

import { Cause } from "effect"
import { catchCauseIf } from "@typed/fx/Fx"
import { failCause, succeed } from "@typed/fx/Fx"

const recovered = catchCauseIf(
  failCause(Cause.die("bad decoder")),
  Cause.hasDies,
  () => succeed("reported")
)

Other public imports

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

Source