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catchTags

Recovers several tagged typed-error variants with one handler table.

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

Follow one execution

This Denied failure selects the Denied handler from the handler table.

Fx timelinecatchTags({ Offline, Denied })catchTags
OperatorcatchTags({ Offline, Denied })
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 first Fail found anywhere in the source Cause is inspected. A listed tag starts exactly one handler Fx and replaces the entire original Cause, including any defects or interrupts composed with that Fail. An untagged or unlisted first Fail, or a Cause with no Fail, propagates intact. Handlers are lazy and contribute their individual errors and service requirements.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const catchTags: {
    <E, Cases extends TaggedCase<E>>(cases: Cases): <A, R>(self: Fx<A, E, R>) => Fx<A | {
        [K in keyof Cases]: CaseSuccess<Cases[K]>;
    }[keyof Cases], Exclude<E, {
        _tag: keyof Cases;
    }> | {
        [K in keyof Cases]: CaseError<Cases[K]>;
    }[keyof Cases], R | {
        [K in keyof Cases]: CaseServices<Cases[K]>;
    }[keyof Cases]>;
    <A, E, R, Cases extends TaggedCase<E>>(self: Fx<A, E, R>, cases: Cases): Fx<A | {
        [K in keyof Cases]: CaseSuccess<Cases[K]>;
    }[keyof Cases], Exclude<E, {
        _tag: keyof Cases;
    }> | {
        [K in keyof Cases]: CaseError<Cases[K]>;
    }[keyof Cases], R | {
        [K in keyof Cases]: CaseServices<Cases[K]>;
    }[keyof Cases]>;
};

Why

A handler table keeps multi-variant recovery exhaustive and preserves the precise success, error, and service unions produced by each selected case. Unlisted variants remain visible in the returned error channel.

Ownership and lifetime

The first Fail found anywhere in the source Cause is inspected. A listed tag starts exactly one handler Fx and replaces the entire original Cause, including any defects or interrupts composed with that Fail. An untagged or unlisted first Fail, or a Cause with no Fail, propagates intact. Handlers are lazy and contribute their individual errors and service requirements.

Examples

import { catchTags } from "@typed/fx/Fx"
import { fail, succeed } from "@typed/fx/Fx"

type Failure =
  | { readonly _tag: "Missing"; readonly id: string }
  | { readonly _tag: "Forbidden" }
const source = fail<Failure>({ _tag: "Missing", id: "42" })
const recovered = catchTags(source, {
  Missing: ({ id }) => succeed(`missing:${id}`),
  Forbidden: () => succeed("forbidden")
})

Other public imports

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

Source