BUG: Aggregation on arrow array return same type.

Signed-off-by: Liang Yan <[email protected]>

Author: liang3zy22

pandas/core/groupby/ops.py

@@ -52,6 +52,7 @@
     maybe_fill,
 )
 
+import pandas as pd
 from pandas.core.frame import DataFrame
 from pandas.core.groupby import grouper
 from pandas.core.indexes.api import (
@@ -837,7 +838,11 @@ def agg_series(
         # test_groupby_empty_with_category gets here with self.ngroups == 0
         #  and len(obj) > 0
 
-        if len(obj) > 0 and not isinstance(obj._values, np.ndarray):
+        if (
+            len(obj) > 0
+            and not isinstance(obj._values, np.ndarray)
+            and not isinstance(obj._values, pd.arrays.ArrowExtensionArray)
+        ):
             # we can preserve a little bit more aggressively with EA dtype
             #  because maybe_cast_pointwise_result will do a try/except
             #  with _from_sequence.  NB we are assuming here that _from_sequence