WHATWG DOM Abort

Elide implements the WHATWG [DOM Living Standard][spec] abort interfaces as globals: AbortController and AbortSignal. They integrate with EventTarget — AbortSignal.prototype inherits from EventTarget.prototype, and addEventListener(..., { signal }) removes the listener automatically when the signal aborts.

[spec]: https://dom.spec.whatwg.org/#aborting-ongoing-activities

`AbortController`

new AbortController()

Calling AbortController(...) without new throws TypeError — per WebIDL, interface objects with constructors must be invoked with new.

Member	Type	Notes
`signal`	`AbortSignal`	Readonly, `[SameObject]` — repeated reads return the same signal instance.
`abort(reason?)`	`undefined`	Marks `signal` as aborted with `reason` and dispatches a trusted `abort` event. Idempotent — later calls are no-ops. When `reason` is omitted, a fresh `new DOMException("The operation was aborted", "AbortError")` is stored (WebIDL signature is `new DOMException(message, name)`).

`AbortSignal`

new AbortSignal() always throws TypeError — signals are only created via AbortController, AbortSignal.abort(...), or AbortSignal.any(...).

Member	Type	Notes
`aborted`	`boolean`	Readonly; `true` once `abort(...)` has been called.
`reason`	`any`	Readonly; the value passed to `abort(...)`, or a default `DOMException("AbortError")`.
`throwIfAborted()`	`undefined`	Throws `reason` if `aborted` is `true`; otherwise a no-op.
`onabort`	`EventHandler`	Get/set the single `abort` event handler. Setting `null` or a non-callable clears it; setting a new function replaces the previous handler.
`addEventListener` / `removeEventListener` / `dispatchEvent`	inherited	Inherited from `EventTarget.prototype` — the signal is itself an `EventTarget`.

Static factories

Method	Type	Notes
`AbortSignal.abort(reason?)`	`AbortSignal`	Returns a fresh, already-aborted signal.
`AbortSignal.any(signals)`	`AbortSignal`	Returns a signal that aborts as soon as any input signal aborts. Inputs must be `AbortSignal`s; if any is already aborted when called, the returned signal is aborted before return.
`AbortSignal.timeout(ms)`	`AbortSignal`	Returns a fresh signal that aborts after `ms` milliseconds with a `TimeoutError` `DOMException` (distinct from the `AbortError` used by `AbortController.abort()`). The argument follows WebIDL `[EnforceRange] unsigned long long` semantics with a practical cap at `Number.MAX_SAFE_INTEGER`: `NaN`, `±Infinity`, negative values, and values above the cap throw `TypeError`. Fractional inputs are truncated toward zero (`1.5 → 1`).

Integration with `addEventListener`

The third argument to EventTarget.addEventListener(type, callback, options) accepts a { signal } property. When present:

If the signal is already aborted, the listener is not registered.
Otherwise the listener is added normally, and the signal arranges for the listener to be removed automatically when the signal aborts.

const target = new EventTarget();
const ctrl = new AbortController();
target.addEventListener("message", onMessage, { signal: ctrl.signal });

// Later — removes the listener, no matter who registered it:
ctrl.abort();

Non-AbortSignal values passed as signal are ignored (they behave as if the property were absent), matching Node.js and browsers.

Example

// AbortSignal.timeout produces a fresh signal that aborts after the given delay.
async function fetchWithTimeout(url, ms) {
  return fetch(url, { signal: AbortSignal.timeout(ms) });
}

// Compose with another cancellation source — typing Ctrl-C, parent shutdown, etc.
const any = AbortSignal.any([userCancel.signal, AbortSignal.timeout(5000)]);

Notes on the implementation

Plain-call AbortController(...) is routed to TypeError via a manual construct?-ternary patch in the generated JSAbortControllerClassBase.java (same pattern as DOMException, the encoding classes and the event classes). The upstream elide-dev/bindgen generator emits this branch automatically on the next regenerate. AbortSignal's "not directly constructible" TypeError is already present in the generated base.
The two classes skip the generated putBuiltinClass and use a custom installAsGlobal in the agent. The generated path consumes a slot in the realm's shared JSObjectFactory.IntrinsicBuilder shape array — that array is sized at JSContext creation from graal-js's own factory count with no public extension point, and non-ordinary subclass layouts (AbortSignalObject / AbortControllerObject extend JSNonProxyObject) collide with graal-js's own JSOrdinaryObject shapes at high slots. installAsGlobal sidesteps that collision by building the factory via JSObjectFactory.createBound, which keeps the shape on the factory itself rather than in the realm-shared array.
The signal option on addEventListener is parsed by EventsOps.parseListenerOptions and consumed by JSEventTarget.addListener through the public AbortOps.registerRemoveOnAbort hook, which calls JSEventTarget.removeListenerByReference from the signal's abort-cleanup list. No public API change to the EventTarget contract; behaviour is additive.