PHPLIB-398: Aggregate with $out should ignore batchSize option

src/Operation/Aggregate.php

@@ -255,7 +255,7 @@ class Aggregate implements Executable
         $hasExplain = ! empty($this->options['explain']);
         $hasOutStage = \MongoDB\is_last_pipeline_operator_out($this->pipeline);
 
-        $command = $this->createCommand($server);
+        $command = $this->createCommand($server, $hasOutStage);
         $options = $this->createOptions($hasOutStage, $hasExplain);
 
         $cursor = ($hasOutStage && ! $hasExplain)
@@ -287,9 +287,10 @@ class Aggregate implements Executable
      * Create the aggregate command.
      *
      * @param Server  $server
+     * @param boolean $hasOutStage
      * @return Command
      */
-    private function createCommand(Server $server)
+    private function createCommand(Server $server, $hasOutStage)
     {
         $cmd = [
             'aggregate' => isset($this->collectionName) ? $this->collectionName : 1,
@@ -325,7 +326,10 @@ class Aggregate implements Executable
         }
 
         if ($this->options['useCursor']) {
-            $cmd['cursor'] = isset($this->options["batchSize"])
+            /* Ignore batchSize if pipeline includes an $out stage, as no
+             * documents will be returned and sending a batchSize of zero could
+             * prevent the pipeline from executing at all. */
+            $cmd['cursor'] = isset($this->options["batchSize"]) && ! $hasOutStage
                 ? ['batchSize' => $this->options["batchSize"]]
                 : new stdClass;
         }

tests/Collection/CrudSpecFunctionalTest.php

@@ -43,6 +43,11 @@ class CrudSpecFunctionalTest extends FunctionalTestCase
         $expectedData = isset($test['outcome']['collection']['data']) ? $test['outcome']['collection']['data'] : null;
         $this->initializeData($initialData, $expectedData);
 
+        if (isset($test['outcome']['collection']['name'])) {
+            $outputCollection = new Collection($this->manager, $this->getDatabaseName(), $test['outcome']['collection']['name']);
+            $outputCollection->drop();
+        }
+
         $result = null;
         $exception = null;
 
@@ -81,7 +86,7 @@ class CrudSpecFunctionalTest extends FunctionalTestCase
      */
     private function assertEquivalentCollections($expectedCollection, $actualCollection)
     {
-        $mi = new MultipleIterator;
+        $mi = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
         $mi->attachIterator(new IteratorIterator($expectedCollection->find()));
         $mi->attachIterator(new IteratorIterator($actualCollection->find()));
 

tests/Operation/AggregateFunctionalTest.php

@@ -2,6 +2,7 @@
 
 namespace MongoDB\Tests\Operation;
 
+use MongoDB\Collection;
 use MongoDB\Driver\BulkWrite;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\WriteConcern;
@@ -14,6 +15,28 @@ use stdClass;
 
 class AggregateFunctionalTest extends FunctionalTestCase
 {
+    public function testBatchSizeIsIgnoredIfPipelineIncludesOutStage()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Aggregate(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [['$out' => $this->getCollectionName() . '.output']],
+                    ['batchSize' => 0]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(array $event) {
+                $this->assertEquals(new stdClass, $event['started']->getCommand()->cursor);
+            }
+        );
+
+        $outCollection = new Collection($this->manager, $this->getDatabaseName(), $this->getCollectionName() . '.output');
+        $outCollection->drop();
+    }
+
     public function testCurrentOpCommand()
     {
         if (version_compare($this->getServerVersion(), '3.6.0', '<')) {
@@ -72,6 +95,9 @@ class AggregateFunctionalTest extends FunctionalTestCase
                 $this->assertObjectNotHasAttribute('writeConcern', $event['started']->getCommand());
             }
         );
+
+        $outCollection = new Collection($this->manager, $this->getDatabaseName(), $this->getCollectionName() . '.output');
+        $outCollection->drop();
     }
 
     public function testEmptyPipelineReturnsAllDocuments()