From f530e53277fee0e91432944754bfd5084afce22c Mon Sep 17 00:00:00 2001
From: Trevor Bergeron <tbergeron@google.com>
Date: Sat, 18 Jan 2025 01:04:27 +0000
Subject: [PATCH] feat: DataFrame.join supports Series other

---
 bigframes/dataframe.py                        |  9 +++++++-
 tests/system/small/test_dataframe.py          | 21 +++++++++++++++++++
 .../bigframes_vendored/pandas/core/frame.py   |  2 +-
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/bigframes/dataframe.py b/bigframes/dataframe.py
index e1bb885558..a4d267fcde 100644
--- a/bigframes/dataframe.py
+++ b/bigframes/dataframe.py
@@ -3039,8 +3039,15 @@ def merge(
         return DataFrame(block)
 
     def join(
-        self, other: DataFrame, *, on: Optional[str] = None, how: str = "left"
+        self,
+        other: Union[DataFrame, bigframes.series.Series],
+        *,
+        on: Optional[str] = None,
+        how: str = "left",
     ) -> DataFrame:
+        if isinstance(other, bigframes.series.Series):
+            other = other.to_frame()
+
         left, right = self, other
 
         if not left.columns.intersection(right.columns).empty:
diff --git a/tests/system/small/test_dataframe.py b/tests/system/small/test_dataframe.py
index 5b94df2446..e7d6ad67e1 100644
--- a/tests/system/small/test_dataframe.py
+++ b/tests/system/small/test_dataframe.py
@@ -2554,6 +2554,27 @@ def test_join_param_on(scalars_dfs, how):
         assert_pandas_df_equal(bf_result, pd_result, ignore_order=True)
 
 
+@all_joins
+def test_df_join_series(scalars_dfs, how):
+    bf_df, pd_df = scalars_dfs
+
+    bf_df_a = bf_df[["string_col", "int64_col", "rowindex_2"]]
+    bf_df_a = bf_df_a.assign(rowindex_2=bf_df_a["rowindex_2"] + 2)
+    bf_series_b = bf_df["float64_col"]
+
+    if how == "cross":
+        with pytest.raises(ValueError):
+            bf_df_a.join(bf_series_b, on="rowindex_2", how=how)
+    else:
+        bf_result = bf_df_a.join(bf_series_b, on="rowindex_2", how=how).to_pandas()
+
+        pd_df_a = pd_df[["string_col", "int64_col", "rowindex_2"]]
+        pd_df_a = pd_df_a.assign(rowindex_2=pd_df_a["rowindex_2"] + 2)
+        pd_series_b = pd_df["float64_col"]
+        pd_result = pd_df_a.join(pd_series_b, on="rowindex_2", how=how)
+        assert_pandas_df_equal(bf_result, pd_result, ignore_order=True)
+
+
 @pytest.mark.parametrize(
     ("by", "ascending", "na_position"),
     [
diff --git a/third_party/bigframes_vendored/pandas/core/frame.py b/third_party/bigframes_vendored/pandas/core/frame.py
index a44d6b629f..c8ca1b74b5 100644
--- a/third_party/bigframes_vendored/pandas/core/frame.py
+++ b/third_party/bigframes_vendored/pandas/core/frame.py
@@ -4384,7 +4384,7 @@ def join(self, other, *, on: Optional[str] = None, how: str) -> DataFrame:
 
         Args:
             other:
-                DataFrame with an Index similar to the Index of this one.
+                DataFrame or Series with an Index similar to the Index of this one.
             on:
                 Column in the caller to join on the index in other, otherwise
                 joins index-on-index. Like an Excel VLOOKUP operation.