Deprecate groupby fillna (#15000)

Deprecated in pandas 2.2 pandas-dev/pandas#55719

Authors:
  - Matthew Roeschke (https://github.com/mroeschke)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: #15000

Author: mroeschke

python/cudf/cudf/core/groupby/groupby.py

@@ -2227,6 +2227,12 @@ def fillna(
         -------
         DataFrame or Series
         """
+        warnings.warn(
+            "groupby fillna is deprecated and "
+            "will be removed in a future version. Use groupby ffill or groupby bfill "
+            "for forward or backward filling instead.",
+            FutureWarning,
+        )
         if inplace:
             raise NotImplementedError("Does not support inplace yet.")
         if limit is not None:
@@ -2244,17 +2250,6 @@ def fillna(
         if method is not None:
             if method not in {"ffill", "bfill"}:
                 raise ValueError("Method can only be of 'ffill', 'bfill'.")
-            # Do not remove until pandas 3.0 support is added.
-            assert (
-                PANDAS_LT_300
-            ), "Need to drop after pandas-3.0 support is added."
-            warnings.warn(
-                f"{type(self).__name__}.fillna with 'method' is "
-                "deprecated and will raise in a future version. "
-                "Use obj.ffill() or obj.bfill() instead.",
-                FutureWarning,
-            )
-
             return getattr(self, method, limit)()
 
         values = self.obj.__class__._from_data(

python/cudf/cudf/tests/test_groupby.py

@@ -20,7 +20,7 @@
 import cudf
 from cudf import DataFrame, Series
 from cudf.api.extensions import no_default
-from cudf.core._compat import PANDAS_GE_200, PANDAS_GE_210
+from cudf.core._compat import PANDAS_GE_200, PANDAS_GE_210, PANDAS_GE_220
 from cudf.core.udf._ops import arith_ops, comparison_ops, unary_ops
 from cudf.core.udf.groupby_typing import SUPPORTED_GROUPBY_NUMPY_TYPES
 from cudf.core.udf.utils import UDFError, precompiled
@@ -2745,10 +2745,10 @@ def test_groupby_fillna_multi_value(nelem):
     }
     # cudf can't fillna with a pandas.Timedelta type
     fill_values["4"] = fill_values["4"].to_numpy()
-
-    expect = pdf.groupby(key_col).fillna(value=fill_values)
-
-    got = gdf.groupby(key_col).fillna(value=fill_values)
+    with expect_warning_if(PANDAS_GE_220):
+        expect = pdf.groupby(key_col).fillna(value=fill_values)
+    with pytest.warns(FutureWarning):
+        got = gdf.groupby(key_col).fillna(value=fill_values)
 
     assert_groupby_results_equal(expect[value_cols], got[value_cols])
 
@@ -2791,11 +2791,12 @@ def test_groupby_fillna_multi_value_df(nelem):
     # cudf can't fillna with a pandas.Timedelta type
     fill_values["4"] = fill_values["4"].to_numpy()
     fill_values = pd.DataFrame(fill_values, index=pdf.index)
-
-    expect = pdf.groupby(key_col).fillna(value=fill_values)
+    with expect_warning_if(PANDAS_GE_220):
+        expect = pdf.groupby(key_col).fillna(value=fill_values)
 
     fill_values = cudf.from_pandas(fill_values)
-    got = gdf.groupby(key_col).fillna(value=fill_values)
+    with pytest.warns(FutureWarning):
+        got = gdf.groupby(key_col).fillna(value=fill_values)
 
     assert_groupby_results_equal(expect[value_cols], got[value_cols])
 
@@ -2812,11 +2813,13 @@ def test_groupby_various_by_fillna(by, data, args):
     ps = pd.Series(data)
     gs = cudf.from_pandas(ps)
 
-    with expect_warning_if(PANDAS_GE_210 and "method" in args):
+    with expect_warning_if(
+        (PANDAS_GE_210 and "method" in args) or PANDAS_GE_220
+    ):
         expect = ps.groupby(by).fillna(**args)
     if isinstance(by, pd.Grouper):
         by = cudf.Grouper(level=by.level)
-    with expect_warning_if("method" in args):
+    with pytest.warns(FutureWarning):
         got = gs.groupby(by).fillna(**args)
 
     assert_groupby_results_equal(expect, got, check_dtype=False)