mypy fixes, add mypy pre-commit hook

Author: honno

.pre-commit-config.yaml

@@ -20,3 +20,7 @@ repos:
   rev: 3.9.2
   hooks:
   - id: flake8
+- repo: https://github.com/pre-commit/mirrors-mypy
+  rev: v0.961
+  hooks:
+  - id: mypy

tests/api.py

@@ -242,9 +242,7 @@ def get_chunks(self, n_chunks: int | None = None) -> Iterable[Column]:
         See `DataFrame.get_chunks` for details on ``n_chunks``.
         """
 
-    def get_buffers(
-        self,
-    ) -> dict[tuple[Buffer, Any], tuple[Buffer, Any] | None, tuple[Buffer, Any] | None]:
+    def get_buffers(self) -> dict[str, Any]:
         """
         Return a dictionary containing the underlying buffers.
 

tests/test_signatures.py

@@ -1,6 +1,6 @@
 from inspect import Parameter, getmembers, isfunction, signature
 from types import FunctionType
-from typing import Callable
+from typing import Callable  # See https://github.com/python/mypy/issues/6864
 
 import pytest
 from hypothesis import assume, given, note, settings
@@ -75,7 +75,7 @@ def _test_signature(func, stub):
 def test_toplevel_dataframe_dunder_dataframe(libinfo: LibraryInfo, data: st.DataObject):
     df = data.draw(libinfo.toplevel_dataframes(), label="df")
     assert hasattr(df, "__dataframe__")
-    assert isinstance(df.__dataframe__, Callable)
+    assert isinstance(df.__dataframe__, Callable)  # type: ignore
     _test_signature(df.__dataframe__, DataFrame.__dataframe__)
 
 
@@ -94,7 +94,7 @@ def test_dataframe_method(
     df = data.draw(libinfo.compliant_dataframes(), label="df")
     assert hasattr(df, stub.__name__)
     method = getattr(df, stub.__name__)
-    assert isinstance(method, Callable)
+    assert isinstance(method, Callable)  # type: ignore
     _test_signature(method, stub)
 
 
@@ -114,7 +114,7 @@ def test_column_method(libinfo: LibraryInfo, stub: FunctionType, data: st.DataOb
     note(f"{col=}")
     assert hasattr(col, stub.__name__)
     method = getattr(col, stub.__name__)
-    assert isinstance(method, Callable)
+    assert isinstance(method, Callable)  # type: ignore
     _test_signature(method, stub)
 
 
@@ -137,5 +137,5 @@ def test_buffer_method(libinfo: LibraryInfo, stub: FunctionType, data: st.DataOb
     note(f"{buf=}")
     assert hasattr(buf, stub.__name__)
     method = getattr(buf, stub.__name__)
-    assert isinstance(method, Callable)
+    assert isinstance(method, Callable)  # type: ignore
     _test_signature(method, stub)

tests/wrappers.py

@@ -301,4 +301,5 @@ def cudf_mock_to_toplevel(mock_df: MockDataFrame) -> cudf.DataFrame:
 for param in libinfo_params:
     if not any(m.name.startswith("skip") for m in param.marks):
         libinfo = param.values[0]
+        assert isinstance(libinfo, LibraryInfo)  # for mypy
         libname_to_libinfo[libinfo.name] = libinfo