Add test to verify null cast in boolean type

lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php

@@ -723,7 +723,7 @@ protected function _getCreateTableSQL($tableName, array $columns, array $options
     private function convertSingleBooleanValue($value, $callback)
     {
         if (null === $value) {
-            return $callback(false);
+            return $callback(null);
         }
 
         if (is_bool($value) || is_numeric($value)) {
@@ -787,6 +787,10 @@ public function convertBooleans($item)
         return $this->doConvertBooleans(
             $item,
             function ($boolean) {
+                if (null === $boolean) {
+                    return 'NULL';
+                }
+
                 return true === $boolean ? 'true' : 'false';
             }
         );
@@ -804,7 +808,7 @@ public function convertBooleansToDatabaseValue($item)
         return $this->doConvertBooleans(
             $item,
             function ($boolean) {
-                return (int) $boolean;
+                return null === $boolean ? null : (int) $boolean;
             }
         );
     }

tests/Doctrine/Tests/DBAL/Functional/Ticket/DBAL630Test.php

@@ -88,4 +88,31 @@ public function testBooleanConversionBoolParamEmulatedPrepares()
 
         $this->assertFalse($row['bool_col']);
     }
+
+    public function testBooleanConversionNullParamEmulatedPrepares()
+    {
+        $this->_conn->exec('CREATE TABLE dbal630_allow_nulls (id SERIAL, bool_col BOOLEAN);');
+
+        $this->_conn->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
+
+        // PDO::PGSQL_ATTR_DISABLE_NATIVE_PREPARED_STATEMENT is deprecated in php 5.6. PDO::ATTR_EMULATE_PREPARES should
+        // be used instead. so should only it be set when it is supported.
+        if (PHP_VERSION_ID < 50600) {
+            $this->_conn->getWrappedConnection()->setAttribute(PDO::PGSQL_ATTR_DISABLE_NATIVE_PREPARED_STATEMENT, true);
+        }
+
+        $platform = $this->_conn->getDatabasePlatform();
+
+        $stmt = $this->_conn->prepare('INSERT INTO dbal630_allow_nulls (bool_col) VALUES(?)');
+        $stmt->bindValue(1, $platform->convertBooleansToDatabaseValue(null));
+        $stmt->execute();
+
+        $id = $this->_conn->lastInsertId('dbal630_id_seq');
+
+        $this->assertNotEmpty($id);
+
+        $row = $this->_conn->fetchAssoc('SELECT bool_col FROM dbal630_allow_nulls WHERE id = ?', array($id));
+
+        $this->assertNull($row['bool_col']);
+    }
 }

tests/Doctrine/Tests/DBAL/Platforms/AbstractPostgreSqlPlatformTestCase.php

@@ -613,6 +613,8 @@ public function pgBooleanProvider()
             array('no', 'false', 0, false),
             array('off', 'false', 0, false),
             array('0', 'false', 0, false),
+
+            array(null, 'NULL', null, null)
         );
     }