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Stefan
4c4a705ce3
`copyEventListenerOptions` copied the caller's options with `{...options}`
before forwarding to the native `addEventListener`. Object spread only
copies own enumerable data properties, whereas the native call reads
each dictionary member via WebIDL — a plain `[[Get]]` per member, which
invokes accessors and ignores enumerability. The copy was therefore
lossy in a way the native call is not:
- `Object.defineProperty(opts, 'passive', { get })` (the shape used by
MDN's passive-listener feature test) — the getter was never invoked,
so libraries that use the feature test fall back to the legacy boolean
and register every listener as non-passive.
- `Object.defineProperty(opts, 'capture', { get: () => true })` — the
listener was silently registered on the bubbling phase.
- `Object.defineProperty(opts, 'once', { get: () => true })` — the
listener fired on every dispatch.
`signal` was already special-cased for `AbortController.prototype.signal`
after #54142; that patch generalises the workaround to every recognised
member.
The copy itself was the correct fix for #54142 (frozen/readonly options)
and is preserved. The fix reads each recognised member from the source
via `[[Get]]` when the spread did not, which recovers accessors and
non-enumerable properties without double-invoking any getter. The list
of recognised members is hoisted to module scope so it isn't allocated
on every `patchEventTarget` invocation.
The call site is reordered to `buildEventListenerOptions(
copyEventListenerOptions(...))` so the passive-events code path also
spreads a normalised data object rather than the caller's raw input.
Fixes #70431
Co-authored-by: Matthieu Riegler <kyro38@gmail.com>