Narrow AsyncAdaptedCursor.fetchone return type to Any | None

The method returns None when the buffered deque is empty, matching the
PEP 249 contract, but the annotation said Any — which swallows the None
case silently at call sites. Align with the sibling dqlitedbapi.Cursor
and dqlitedbapi.aio.AsyncCursor, which both type fetchone as
tuple[Any, ...] | None, and pin the annotation so a future widening is
caught in tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/sqlalchemydqlite/aio.py

@@ -133,7 +133,11 @@ def executemany(self, operation: str, seq_of_parameters: Iterable[Sequence[Any]]
         finally:
             await_only(cursor.close())
 
-    def fetchone(self) -> Any:
+    def fetchone(self) -> Any | None:
+        # Narrow from ``Any`` so callers understand None is a legitimate
+        # return on exhaustion (PEP 249 contract, mirroring the
+        # dqlitedbapi sync / async cursors that already type this as
+        # ``tuple[Any, ...] | None``). Runtime behaviour unchanged.
         if self._rows:
             return self._rows.popleft()
         return None

tests/test_async_adapter.py

@@ -380,6 +380,18 @@ def test_fetchone_pops_left(self) -> None:
         assert cursor.fetchone() == (3,)  # type: ignore[attr-defined]
         assert cursor.fetchone() is None  # type: ignore[attr-defined]
 
+    def test_fetchone_return_annotation_admits_none(self) -> None:
+        """Pin ``fetchone -> Any | None`` so a silent widening to
+        ``Any`` (which hides the None-on-exhaustion case from callers)
+        is caught here rather than at a downstream type-check site.
+        """
+        import typing
+
+        hints = typing.get_type_hints(AsyncAdaptedCursor.fetchone)
+        # typing.get_type_hints resolves ``Any | None`` to the runtime
+        # union; compare as a set so ordering is ignored.
+        assert set(typing.get_args(hints["return"])) == {typing.Any, type(None)}
+
     def test_fetchmany_default_uses_arraysize(self) -> None:
         cursor = self._cursor_with_rows([(1,), (2,), (3,), (4,)])
         cursor.arraysize = 2  # type: ignore[attr-defined]