Fx.ensuring · API reference

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Run close after completion, failure, or interruption; output completion waits for cleanup.

Fx timelineensuring(close)ensuring

Source

Operatorensuring(close)

Lifecycle

Values

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 finalizer runs exactly once after normal completion, failure, defect, or interruption of the source run and follows Effect’s ensuring finalization semantics. Its never typed-error channel does not make it incapable of defecting or being interrupted: a finalizer defect can fail a successful run or combine with the source Cause. Its services are required for the subscription.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.ensuring 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 ensuring: {
    <R2>(finalizer: Effect.Effect<void, never, R2>): <A, E, R>(self: Fx<A, E, R>) => Fx<A, E, R | R2>;
    <A, E, R, R2>(self: Fx<A, E, R>, finalizer: Effect.Effect<void, never, R2>): Fx<A, E, R | R2>;
};

Why

Resources sometimes belong to the subscription as a whole rather than to individual values. ensuring attaches unconditional teardown without changing the source’s success or typed-error channels.

Ownership and lifetime

Examples

import { Effect } from "effect"
import { ensuring } from "@typed/fx/Fx"
import { succeed } from "@typed/fx/Fx"

const observed = ensuring(succeed("ready"), Effect.log("subscription closed"))

A `never` typed-error channel can still contain a defect
```ts
import { Effect } from "effect"
import { ensuring } from "@typed/fx/Fx"
import { succeed } from "@typed/fx/Fx"

const defectiveFinalizer = ensuring(succeed("ready"), Effect.die("close failed"))
```

Other public imports

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

ensuring from @typed/fx/Fx