Fix data loss on multiple Result#rewind() calls

src/Adapter/Driver/Pdo/Result.php

@@ -201,9 +201,11 @@ public function rewind()
                 'This result is a forward only result set, calling rewind() after moving forward is not supported'
             );
         }
-        $this->currentData     = $this->resource->fetch($this->fetchMode);
-        $this->currentComplete = true;
-        $this->position        = 0;
+        if (! $this->currentComplete) {
+            $this->currentData     = $this->resource->fetch($this->fetchMode);
+            $this->currentComplete = true;
+        }
+        $this->position = 0;
     }
 
     /**

test/unit/Adapter/Driver/Pdo/ResultTest.php

@@ -5,9 +5,11 @@
 use Laminas\Db\Adapter\Driver\Pdo\Result;
 use Laminas\Db\Adapter\Exception\InvalidArgumentException;
 use PDO;
+use PDOStatement;
 use PHPUnit\Framework\TestCase;
 use stdClass;
 
+use function assert;
 use function uniqid;
 
 /**
@@ -80,4 +82,35 @@ public function testFetchModeRange()
         self::assertEquals(11, $result->getFetchMode());
         self::assertInstanceOf('stdClass', $result->current());
     }
+
+    public function testMultipleRewind()
+    {
+        $data     = [
+            ['test' => 1],
+            ['test' => 2],
+        ];
+        $position = 0;
+
+        $stub = $this->getMockBuilder('PDOStatement')->getMock();
+        assert($stub instanceof PDOStatement); // to suppress IDE type warnings
+        $stub->expects($this->any())
+            ->method('fetch')
+            ->will($this->returnCallback(function () use ($data, &$position) {
+                return $data[$position++];
+            }));
+        $result = new Result();
+        $result->initialize($stub, null);
+
+        $result->rewind();
+        $result->rewind();
+
+        $this->assertEquals(0, $result->key());
+        $this->assertEquals(1, $position);
+        $this->assertEquals($data[0], $result->current());
+
+        $result->next();
+        $this->assertEquals(1, $result->key());
+        $this->assertEquals(2, $position);
+        $this->assertEquals($data[1], $result->current());
+    }
 }

test/unit/ResultSet/AbstractResultSetTest.php

@@ -3,13 +3,17 @@
 namespace LaminasTest\Db\ResultSet;
 
 use ArrayIterator;
+use Laminas\Db\Adapter\Driver\Pdo\Result;
 use Laminas\Db\Adapter\Driver\ResultInterface;
 use Laminas\Db\ResultSet\AbstractResultSet;
 use Laminas\Db\ResultSet\Exception\InvalidArgumentException;
 use Laminas\Db\ResultSet\Exception\RuntimeException;
+use PDOStatement;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
+use function assert;
+
 class AbstractResultSetTest extends TestCase
 {
     /** @var MockObject */
@@ -266,4 +270,53 @@ public function testBufferIterations()
         $data = $resultSet->current();
         self::assertEquals(3, $data['id']);
     }
+
+    /**
+     * Test multiple iterations with buffer with multiple rewind() calls
+     *
+     * @group issue-6845
+     */
+    public function testMultipleRewindBufferIterations()
+    {
+        $resultSet = $this->getMockForAbstractClass(AbstractResultSet::class);
+        $result    = new Result();
+        $stub      = $this->getMockBuilder(PDOStatement::class)->getMock();
+        $data      = new ArrayIterator([
+            ['id' => 1, 'name' => 'one'],
+            ['id' => 2, 'name' => 'two'],
+            ['id' => 3, 'name' => 'three'],
+        ]);
+        assert($stub instanceof PDOStatement); // to suppress IDE type warnings
+        $stub->expects($this->any())
+            ->method('fetch')
+            ->will($this->returnCallback(function () use ($data) {
+                $r = $data->current();
+                $data->next();
+                return $r;
+            }));
+        $result->initialize($stub, null);
+        $result->rewind();
+        $result->rewind();
+        $resultSet->initialize($result);
+        $resultSet->buffer();
+        $resultSet->rewind();
+        $resultSet->rewind();
+
+        $data = $resultSet->current();
+        self::assertEquals(1, $data['id']);
+        $resultSet->next();
+        $data = $resultSet->current();
+        self::assertEquals(2, $data['id']);
+
+        $resultSet->rewind();
+        $resultSet->rewind();
+        $data = $resultSet->current();
+        self::assertEquals(1, $data['id']);
+        $resultSet->next();
+        $data = $resultSet->current();
+        self::assertEquals(2, $data['id']);
+        $resultSet->next();
+        $data = $resultSet->current();
+        self::assertEquals(3, $data['id']);
+    }
 }