feat: support Series.dot on a DataFrame input

Author: shobsi

bigframes/series.py

@@ -680,6 +680,17 @@ def rdivmod(self, other) -> Tuple[Series, Series]:  # type: ignore
         return (self.rfloordiv(other), self.rmod(other))
 
     def __matmul__(self, other):
+        if isinstance(other, bigframes.dataframe.DataFrame):
+            return Series(
+                [
+                    pandas.NA if other[col].isna().any() else (self * other[col]).sum()
+                    for col in other.columns
+                ],
+                index=other.columns,
+                name=self.name,
+            )
+
+        # At this point other must be a Series
         return (self * other).sum()
 
     dot = __matmul__

tests/system/small/test_series.py

@@ -22,6 +22,7 @@
 import pyarrow as pa  # type: ignore
 import pytest
 
+import bigframes.dataframe as dataframe
 import bigframes.pandas
 import bigframes.series as series
 from tests.system.utils import assert_pandas_df_equal, assert_series_equal
@@ -2266,6 +2267,30 @@ def test_dot(scalars_dfs):
     assert bf_result == pd_result
 
 
+def test_dot_df(scalars_dfs):
+    scalars_df, scalars_pandas_df = scalars_dfs
+    bf_result = scalars_df["int64_too"] @ scalars_df[["int64_col", "int64_too"]]
+    pd_result = (
+        scalars_pandas_df["int64_too"] @ scalars_pandas_df[["int64_col", "int64_too"]]
+    )
+
+    pd.testing.assert_series_equal(
+        bf_result.to_pandas(), pd_result, check_index_type=False, check_dtype=False
+    )
+
+
+def test_dot_df_inline(scalars_dfs):
+    left = [10, 11, 12, 13]  # series data
+    right = [[0, 1], [-2, 3], [4, -5], [6, 7]]  # dataframe data
+
+    bf_result = series.Series(left) @ dataframe.DataFrame(right)
+    pd_result = pd.Series(left) @ pd.DataFrame(right)
+
+    pd.testing.assert_series_equal(
+        bf_result.to_pandas(), pd_result, check_index_type=False, check_dtype=False
+    )
+
+
 @pytest.mark.parametrize(
     ("left", "right", "inclusive"),
     [