PHPLIB-1518 WriteResult::get*Count() always return an int on acknowledged result

[GromNaN]

Fix PHPLIB-1518

I chose to rely on the driver exception thrown by mongodb/mongo-php-driver#1687

[alcaeus]

LGTM, but we may want to consider unacknowledged writes in rename.

[alcaeus]

I'm not sure we should consider using unacknowledged writes a valid use case, but in case we do there's a functional change here. If we want to preserve the option to use unacknowledged writes with GridFS, we should check isAcknowledged instead of relying on the null value from getMatchedCount:

Suggested change

	// If the update resulted in no modification, it's possible that the
	// file did not exist, in which case we must raise an error.
	if ($updateResult->getMatchedCount() !== 1) {
	/* If the update resulted in no modification, it's possible that the
	* file did not exist, in which case we must raise an error. Checking
	* the write result's matched count will be most efficient, but fall
	* back to a findOne operation if necessary (i.e. legacy writes).
	*/
	$found = $updateResult->isAcknowledged()
	? $updateResult->getMatchedCount() === 1
	: $this->collectionWrapper->findFileById($id) !== null;
	if (! $found) {

[GromNaN]

In that case, that's a fix to backport to v1.x, as it already throws an exception when there is an unacknowledged operation.

[alcaeus]

In that case, let's defer to a separate PR, as this does PR not change existing behaviour.

[jmikola]

let's defer to a separate PR

I assume a ticket needs to be created for this. Please cross-reference it here after doing so.

[GromNaN]

I just realized that this second if ($updateResult->getMatchedCount() !== 1) is always true after if ($updateResult->getModifiedCount() === 1) return;.

Do you know what are the "legacy writes" that are mentioned in the comment?

[jmikola]

Legacy opcodes (e.g. OP_UPDATE), which were removed in MongoDB 6.0. At this point, drivers may still use them for unacknowledged writes but all acknowledged writes are guaranteed to use OP_MSG and the corresponding write commands (e.g. update).

[GromNaN]

I did not update the UPGRADE file, there is nothing to upgrade.