fix: Fix Series.to_frame generating string label instead of int where name is None (#1118)

Author: TrevorBergeron

Diff for: bigframes/core/indexers.py

@@ -375,7 +375,7 @@ def _perform_loc_list_join(
     if isinstance(series_or_dataframe, bigframes.series.Series):
         _struct_accessor_check_and_warn(series_or_dataframe, keys_index)
         original_name = series_or_dataframe.name
-        name = series_or_dataframe.name if series_or_dataframe.name is not None else "0"
+        name = series_or_dataframe.name if series_or_dataframe.name is not None else 0
         result = typing.cast(
             bigframes.series.Series,
             series_or_dataframe.to_frame()._perform_join_by_index(
@@ -468,7 +468,7 @@ def _iloc_getitem_series_or_dataframe(
         if isinstance(series_or_dataframe, bigframes.series.Series):
             original_series_name = series_or_dataframe.name
             series_name = (
-                original_series_name if original_series_name is not None else "0"
+                original_series_name if original_series_name is not None else 0
             )
             df = series_or_dataframe.to_frame()
         original_index_names = df.index.names

Diff for: bigframes/series.py

@@ -1651,7 +1651,7 @@ def to_frame(self, name: blocks.Label = None) -> bigframes.dataframe.DataFrame:
         provided_name = name if name else self.name
         # To be consistent with Pandas, it assigns 0 as the column name if missing. 0 is the first element of RangeIndex.
         block = self._block.with_column_labels(
-            [provided_name] if provided_name else ["0"]
+            [provided_name] if provided_name else [0]
         )
         return bigframes.dataframe.DataFrame(block)
 

Diff for: bigframes/session/__init__.py

@@ -922,7 +922,7 @@ def read_pickle(
 
         if isinstance(pandas_obj, pandas.Series):
             if pandas_obj.name is None:
-                pandas_obj.name = "0"
+                pandas_obj.name = 0
             bigframes_df = self._read_pandas(pandas_obj.to_frame(), "read_pickle")
             return bigframes_df[bigframes_df.columns[0]]
         return self._read_pandas(pandas_obj, "read_pickle")

Diff for: tests/system/small/test_series.py

@@ -2790,6 +2790,15 @@ def test_to_frame(scalars_dfs):
     assert_pandas_df_equal(bf_result, pd_result)
 
 
+def test_to_frame_no_name(scalars_dfs):
+    scalars_df, scalars_pandas_df = scalars_dfs
+
+    bf_result = scalars_df["int64_col"].rename(None).to_frame().to_pandas()
+    pd_result = scalars_pandas_df["int64_col"].rename(None).to_frame()
+
+    assert_pandas_df_equal(bf_result, pd_result)
+
+
 def test_to_json(gcs_folder, scalars_df_index, scalars_pandas_df_index):
     path = gcs_folder + "test_series_to_json*.jsonl"
     scalars_df_index["int64_col"].to_json(path, lines=True, orient="records")