Method Bucket::upsertMulti() Silently Fail On Locked Items

For following test code

<?php

// ...

$key1       = 'key1';

$key2       = 'key2';

$collection->upsertMulti([[$key1, 'dummy'], [$key2, 'dummy']]);

$collection->getAndLock($key2, 10);

$collection->upsertMulti([[$key1, 'changed'], [$key2, 'changed']]);

var_dump(array_map(fn ($doc) => $doc->content(), $collection->getMulti([$key1, $key2])));

Ideally, it should return an array of two items, where first item is a valid Couchbase document, and the 2nd one is an error document (with error code COUCHBASE_KEY_EEXISTS), as in previous major versions of Couchbase.

However, it returns the following output under Couchbase v4.1.6:

array(2) {

  [0]=>

  string(7) "changed"

  [1]=>

  string(5) "dummy"

} 

As we can see, the batch operation fails to update the 2nd item silently.