[Cursor] the current method does not return anything!

[ziaratban]

After the last fetch, the current method of MongoDB\Driver\Cursor must be return null but not returns anything.(according to the doc).

Q	A
OS	CentOS 8
PHP	7.4.12
MongoDB extension version	1.9.0
MongoDB server	MongoDB Enterprise 4.4.1
MongoDB environment	Replica Set

Test.php

<?php
$mng = new \MongoDB\Driver\Manager('mongodb://user:pass@127.0.0.1:27017/myDB');
$mng->selectServer($mng->getReadPreference());
$cursor = $mng->executeQuery('myDB.myCollection',new \MongoDB\Driver\Query([],['batchSize' => 100]));
$cursor->SetTypeMap([
    'root' => 'array',
    'document' => 'array'
]);
var_dump($cursor->isDead());
var_dump($cursor->getId());
$cursor->rewind();
while(true){
    $row = $cursor->current();
    var_dump($row);
    $cursor->next();
}

root# php Test.php

output

bool(false)
object(MongoDB\Driver\CursorId)#4 (1) {
  ["id"]=>
  int(0)
}
array(13) {
...
}
array(13) {
...
}
PHP Notice:  Undefined variable: row in Test.php on line 14
NULL
PHP Fatal error:  Uncaught MongoDB\Driver\Exception\RuntimeException: Cannot advance a completed or failed cursor. in Test.php:15
Stack trace:
#0 Test.php(15): MongoDB\Driver\Cursor->next()
#1 {main}
  thrown in Test.php on line 15

[alcaeus]

Hi @ziaratban! Thanks for reporting this. Are you running the latest version (1.9.0)? That version introduced changes to cursor iteration by implementing the Iterator interface, so that might have something to do with this. I'll investigate this and report back.

[ziaratban]

Hi @alcaeus.
thanks for your reply.
yes. i am certain.

[jmikola]

@alcaeus I believe this behavior may be expected given the implementation of Cursor::current(). return_value is only set if data is non-null, so perhaps an earlier guard statement with RETURN_NULL() is needed.

That said, @ziaratban should only call current() if valid() returns true, per PHP's own contract for the Iterator interface.

[agolin95]

Tracked in https://jira.mongodb.org/browse/PHPC-1713

[alcaeus]

Will be fixed in the upcoming patch release.