attachStream method

void attachStream(Object target, Future<void> cancel(Object))

Transfers close notification to one stream without strongly rooting it.

cancel must be an unbound function: the notice keeps only a weak target, but retains this operation so an abandoned target cannot strand leases.

Implementation

void attachStream(Object target, Future<void> Function(Object) cancel) {
  if (_released || _stream != null) {
    throw StateError('Resource operation cannot attach another stream.');
  }
  final notice = _ResourceStreamNotice(this, target, cancel);
  _stream = notice;
  (_group.streams ??= []).add(notice);
  for (final control in _group.leases.keys.toList(growable: false)) {
    notice.attach(control);
    if (_released) return;
  }
  // All links exist before cancellation can synchronously reenter cleanup.
  for (final control in notice.controls.toList(growable: false)) {
    if (_released) break;
    if (control.state != ResourceState.open) control._cancelStreams([notice]);
  }
}