React\Promise\uncancellable()

example.php

$cancellable = new Promise(function () { }, function ($resolve, $reject) { $reject(); });
$uncancellable = uncancellable($cancellable);

assertPending($cancellable);
assertPending($uncancellable);

// this is a NO-OP
$uncancellable->cancel();
assertPending($cancellable);
assertPending($uncancellable);

// this *still* works
$cancellable->cancel();
assertSettled($cancellable);
assertSettled($uncancellable);

uncancellable.php

function uncancellable(ExtendedPromiseInterface $promise)
{
    return new Promise(function ($resolve, $reject) use ($promise) {
        $promise->done($resolve, $reject);
    });
}