Fix: Ensure that connection is closed when using context manager

When using the context manager on the Gmp class which determines the
supported GMP version ensure that the opened connection is closed when
leaving the context.

Fixes #659

Author: bjoernricks

gvm/protocols/gmp.py

@@ -19,7 +19,8 @@
 """
 Module for communication with gvmd
 """
-from typing import Any, Optional, Callable, Union
+from types import TracebackType
+from typing import Any, Optional, Callable, Union, Type
 
 from gvm.errors import GvmError
 
@@ -114,8 +115,17 @@ def determine_supported_gmp(self) -> SUPPORTED_GMP_VERSIONS:
         return gmp_class(self._connection, transform=self._gmp_transform)
 
     def __enter__(self):
-        gmp = self.determine_supported_gmp()
+        self._gmp = self.determine_supported_gmp()
 
-        gmp.connect()
+        self._gmp.connect()
 
-        return gmp
+        return self._gmp
+
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_value: Optional[BaseException],
+        traceback: Optional[TracebackType],
+    ) -> Any:
+        self._gmp.disconnect()
+        self._gmp = None

tests/protocols/gmp/test_context_manager.py

@@ -17,6 +17,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import unittest
+from unittest.mock import MagicMock, patch
 
 from tests.protocols import GmpTestCase
 
@@ -115,6 +116,21 @@ def test_invalid_response(self):
             with self.gmp:
                 pass
 
+    @patch("gvm.protocols.gmp.Gmpv214")
+    def test_connect_disconnect(self, gmp_mock: MagicMock):
+        self.connection.read.return_value(
+            '<get_version_response status="200" status_text="OK">'
+            '<version>21.04</version>'
+            '</get_version_response>'
+        )
+
+        with self.gmp:
+            gmp_mock.assert_called_once()
+
+        mock_instance = gmp_mock.return_value
+        mock_instance.connect.assert_called_once()
+        mock_instance.disconnect.assert_called_once()
+
 
 if __name__ == '__main__':
     unittest.main()