Fix do_ping to close cursor in finally block

Ensure cursor is always closed even when execute raises, preventing
resource leaks on connection health checks.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/sqlalchemydqlite/base.py

@@ -134,13 +134,14 @@ def is_disconnect(self, e: Any, connection: Any, cursor: Any) -> bool:
 
     def do_ping(self, dbapi_connection: Any) -> bool:
         """Check if the connection is still alive."""
+        cursor = dbapi_connection.cursor()
         try:
-            cursor = dbapi_connection.cursor()
             cursor.execute("SELECT 1")
-            cursor.close()
             return True
         except Exception:
             return False
+        finally:
+            cursor.close()
 
     def _get_server_version_info(self, connection: Any) -> tuple[int, ...]:
         """Return the server version as a tuple.

tests/test_dialect.py

@@ -326,6 +326,58 @@ def test_set_isolation_level_silent_for_none(self) -> None:
         assert len(w) == 0
 
 
+class TestDoPing:
+    def test_cursor_closed_in_finally(self) -> None:
+        """do_ping must close cursor in a finally block."""
+        import ast
+        import inspect
+        import textwrap
+
+        source = textwrap.dedent(inspect.getsource(DqliteDialect.do_ping))
+        tree = ast.parse(source)
+
+        has_finally_close = False
+        for node in ast.walk(tree):
+            if isinstance(node, ast.Try) and node.finalbody:
+                for stmt in ast.walk(node):
+                    if isinstance(stmt, ast.Call):
+                        func_node = stmt.func
+                        if isinstance(func_node, ast.Attribute) and func_node.attr == "close":
+                            has_finally_close = True
+
+        assert has_finally_close, "cursor.close() should be in a finally block in do_ping"
+
+    def test_ping_returns_true_on_success(self) -> None:
+        """do_ping should return True when query succeeds."""
+        from unittest.mock import MagicMock
+
+        dialect = DqliteDialect()
+        mock_conn = MagicMock()
+        assert dialect.do_ping(mock_conn) is True
+
+    def test_ping_returns_false_on_error(self) -> None:
+        """do_ping should return False when query fails."""
+        from unittest.mock import MagicMock
+
+        dialect = DqliteDialect()
+        mock_conn = MagicMock()
+        mock_conn.cursor.return_value.execute.side_effect = RuntimeError("boom")
+        assert dialect.do_ping(mock_conn) is False
+
+    def test_ping_closes_cursor_even_on_error(self) -> None:
+        """do_ping must close cursor even when execute fails."""
+        from unittest.mock import MagicMock
+
+        dialect = DqliteDialect()
+        mock_conn = MagicMock()
+        mock_cursor = MagicMock()
+        mock_cursor.execute.side_effect = RuntimeError("boom")
+        mock_conn.cursor.return_value = mock_cursor
+
+        dialect.do_ping(mock_conn)
+        mock_cursor.close.assert_called_once()
+
+
 class TestURLParsing:
     def test_parse_basic_url(self) -> None:
         url = URL.create("dqlite", host="localhost", port=9001, database="test")