Session.undo ​

Contract 2.0.0 · package sha256 a857eca95b35921109faf997094bb4192f12527d9d0fcd4be7e97f06425bad6e · generated from configurator-runtime.d.ts by services/onsite-scripter/scripts/build-contract-docs.mjs; edit the source, not this file.

Method of Session · inherited by testing.FakeSession · stable · since 2.0.0 · called as session.undo

undo(options?: WriteOptions): Promise<Report>;

Undoes the last committed step (recorded). In the write queue: it runs after the writes called before it. An undo that needs no load commits before the next frame. It ends an open history.group() at its call, so at its turn it undoes the group's whole step. Outcome: 'committed', or 'refused' with reason 'empty'. It always moves the history pointer: a step whose change is look-only commits look-only; a step whose result equals the current state (its owner was disposed) resolves 'committed' with changed: false, lists 'owner-disposed' in problems and fires only 'history:changed' (spec section 6.1, O9). A reload that fails is not equal: the undo commits with the node back in the model, unloaded, and 'asset-failed' in problems (spec section 6.4). The one exception: when applying it fails inside the runtime, it resolves 'rolled-back' with reason 'internal-error' and the pointer and the step stay where they were (spec section 6.4). Errors: never rejects for an empty history (that is 'refused' / 'empty'); rejects AbortError when signal aborts first.

Options ​

Abort (signal) ​

This call is a write (SignalOption.signal, the kinds of call).

A write: before the commit point it rolls back and rejects AbortError; after it, no effect, except that a running camera move stops where the last frame drew it (CameraMoveOptions).

Through a tx the commit point is the transaction's: aborting a write still loading rejects AbortError and stages nothing (catch it: unobserved, it rolls the transaction back, spec section 6.1, O6); aborting one already staged unstages it, its paths keeping the latest other write to them as after a failed savepoint (O7), and its Promise stays resolved 'staged'.

Example ​

Imports: values (has, validate, the Holo*Error classes, the pure helpers) from @holostep-configurators/runtime-client, types from @holostep-configurators/runtime-client/contract, /math and /testing names from those entries; boot from the runtime module the root's loadRuntimeAtFloor resolves to. A type your page defines is your app's: declare it there, never import it from the package.

Compiled under the contract's strict settings (examples/declaration/05-Session.undo.ts):

import type { Session } from '@holostep-configurators/runtime-client/contract';
declare const session: Session;
declare const signal: AbortSignal;
declare const undoButton: HTMLButtonElement;
undoButton.addEventListener('click', () => {
  // 'refused' / 'empty' when there is nothing to undo
  void session.undo({ actor: 'shopper', origin: 'undo-button' });
}, { signal });
session.on('history:changed', ({ canUndo, undoLabel }) => {
  undoButton.disabled = !canUndo;
  undoButton.title = undoLabel ? `Undo ${undoLabel}` : '';
}, { signal });

Generic-API test (spec 3.1) ​