Fix bug join operation with non-annotating table (#864)

fix bug join non-annotating table wrong region metadata

src/spatialdata/_core/query/relational_query.py

@@ -143,6 +143,7 @@ def _(
 
 
 # TODO: replace function use throughout repo by `join_sdata_spatialelement_table`
+# TODO: benchmark against join operations before removing
 def _filter_table_by_elements(
     table: AnnData | None, elements_dict: dict[str, dict[str, Any]], match_rows: bool = False
 ) -> AnnData | None:
@@ -312,6 +313,8 @@ def _right_exclusive_join_spatialelement_table(
     element_dict: dict[str, dict[str, Any]], table: AnnData, match_rows: Literal["left", "no", "right"]
 ) -> tuple[dict[str, Any], AnnData | None]:
     regions, region_column_name, instance_key = get_table_keys(table)
+    if isinstance(regions, str):
+        regions = [regions]
     groups_df = table.obs.groupby(by=region_column_name, observed=False)
     mask = []
     for element_type, name_element in element_dict.items():
@@ -350,6 +353,8 @@ def _right_join_spatialelement_table(
     if match_rows == "left":
         warnings.warn("Matching rows 'left' is not supported for 'right' join.", UserWarning, stacklevel=2)
     regions, region_column_name, instance_key = get_table_keys(table)
+    if isinstance(regions, str):
+        regions = [regions]
     groups_df = table.obs.groupby(by=region_column_name, observed=False)
     for element_type, name_element in element_dict.items():
         for name, element in name_element.items():
@@ -380,6 +385,8 @@ def _inner_join_spatialelement_table(
     element_dict: dict[str, dict[str, Any]], table: AnnData, match_rows: Literal["left", "no", "right"]
 ) -> tuple[dict[str, Any], AnnData]:
     regions, region_column_name, instance_key = get_table_keys(table)
+    if isinstance(regions, str):
+        regions = [regions]
     obs = table.obs.reset_index()
     groups_df = obs.groupby(by=region_column_name, observed=False)
     joined_indices = None
@@ -424,6 +431,8 @@ def _left_exclusive_join_spatialelement_table(
     element_dict: dict[str, dict[str, Any]], table: AnnData, match_rows: Literal["left", "no", "right"]
 ) -> tuple[dict[str, Any], AnnData | None]:
     regions, region_column_name, instance_key = get_table_keys(table)
+    if isinstance(regions, str):
+        regions = [regions]
     groups_df = table.obs.groupby(by=region_column_name, observed=False)
     for element_type, name_element in element_dict.items():
         for name, element in name_element.items():
@@ -457,6 +466,8 @@ def _left_join_spatialelement_table(
     if match_rows == "right":
         warnings.warn("Matching rows 'right' is not supported for 'left' join.", UserWarning, stacklevel=2)
     regions, region_column_name, instance_key = get_table_keys(table)
+    if isinstance(regions, str):
+        regions = [regions]
     obs = table.obs.reset_index()
     groups_df = obs.groupby(by=region_column_name, observed=False)
     joined_indices = None