GH1339 Allow DataFrame.groupby.aggregate with unpacked dictionary

pandas-stubs/core/groupby/generic.pyi

@@ -264,6 +264,13 @@ class DataFrameGroupBy(GroupBy[DataFrame], Generic[ByT, _TT]):
         engine_kwargs: WindowingEngineKwargs = ...,
         **kwargs,
     ) -> DataFrame: ...
+    @overload
+    def aggregate(
+        self,
+        func: AggFuncTypeFrame | None = None,
+        /,
+        **kwargs,
+    ) -> DataFrame: ...
     agg = aggregate
     @overload
     def transform(

tests/test_groupby.py

@@ -1123,3 +1123,19 @@ def add_constant_to_mean(group: DataFrame, constant: int) -> DataFrame:
             add_constant_to_mean,
             constant="5",  # type: ignore[call-overload] # pyright: ignore[reportCallIssue, reportArgumentType]
         )
+
+
+def test_frame_groupby_aggregate() -> None:
+    """Test DataFrame.groupby.aggregate (GH1339)."""
+    df = DataFrame(
+        {
+            "a": [1, 2, 3],
+            "b": [4, 5, 6],
+            "c": [7, 8, 9],
+        }
+    )
+
+    dico = {"a": ("a", "mean")}
+
+    check(assert_type(df.groupby("b").agg(a=("a", "mean")), DataFrame), DataFrame)
+    check(assert_type(df.groupby("b").agg(**dico), DataFrame), DataFrame)