fix nw.LazyFrame missing _version ClassVar

Author: camriddell

narwhals/dataframe.py

@@ -2361,6 +2361,8 @@ class LazyFrame(BaseFrame[LazyFrameT]):
         ```
     """
 
+    _version: ClassVar[Version] = Version.MAIN
+
     @property
     def _compliant(self) -> CompliantLazyFrame[Any, LazyFrameT, Self]:
         return self._compliant_frame

narwhals/stable/v1/__init__.py

@@ -258,6 +258,8 @@ def _l1_norm(self) -> Self:
 
 
 class LazyFrame(NwLazyFrame[IntoLazyFrameT]):
+    _version = Version.V1
+
     @inherit_doc(NwLazyFrame)
     def __init__(self, df: Any, *, level: Literal["full", "lazy", "interchange"]) -> None:
         assert df._version is Version.V1  # noqa: S101

narwhals/stable/v2/__init__.py

@@ -241,6 +241,8 @@ def is_unique(self) -> Series[Any]:
 
 
 class LazyFrame(NwLazyFrame[IntoLazyFrameT]):
+    _version = Version.V2
+
     @inherit_doc(NwLazyFrame)
     def __init__(self, df: Any, *, level: Literal["full", "lazy", "interchange"]) -> None:
         assert df._version is Version.V2  # noqa: S101

tests/v1_test.py

@@ -621,7 +621,7 @@ def test_lazyframe_recursive_v1() -> None:
 
     pl_frame = pl.DataFrame({"a": [1, 2, 3]}).lazy()
     nw_frame = nw_v1.from_native(pl_frame)
-    with pytest.raises(AttributeError):
+    with pytest.raises(AssertionError):
         nw_v1.LazyFrame(nw_frame, level="lazy")
 
     nw_frame_early_return = nw_v1.from_native(nw_frame)