ui-router-signals

TC39 Signals for UI-Router: a framework-agnostic signal mirror of the router's current state, through signal-polyfill.

The design is tracked in #1157. lit-ui-router-signals builds Lit controllers on it.

Installation

npm install ui-router-signals signal-polyfill

Features

• RouterSignals: one RouteSnapshot per successful transition, in a Signal.State. route, current, params and transition are read-only Signal.Computeds over it, and the tracked includes() answers for that settled snapshot, not the live router. pending and error sit beside the snapshot, fed by one onStart hook: pending is the newest transition still in flight, set on start and cleared when that transition settles, however it settles, unless a newer one has started; error is that transition's RejectType.ERROR rejection, cleared when the next transition starts. One instance (and its transition hooks) per router via RouterSignals.for(router).
• RouteTypes: an empty interface an app or a registry fills in by module augmentation. Its snapshot member types route, so a snapshot whose includes(name) is a type predicate narrows current and params. Empty, route holds a RouteSnapshot.
• watchSelection: watches a selector through a Signal.Computed and hands each new value to a callback, once synchronously and then in a microtask after any source changes. A watcher's notify callback may not read signals, so it schedules the read; several synchronous sets deliver one change.

Loading and error state

import { RouterSignals, watchSelection } from 'ui-router-signals';

const signals = RouterSignals.for(router);

const stop = watchSelection(
  () =>
    signals.pending.get() ? 'loading' : signals.error.get() ? 'error' : 'idle',
  undefined,
  (status) => (document.body.dataset.routeStatus = status),
);

Dependencies

@uirouter/core and signal-polyfill are peer dependencies. lit and lit-ui-router are not, and the bundleProbe claim in package.json holds the entry free of them. Every signal consumer in a bundle needs the same copy of signal-polyfill; two copies keep two separate signal graphs.