Implicit concatenation: Ensure backward compatibility

Author: geoo89

src/rpft/parsers/creation/contentindexparser.py

@@ -219,9 +219,11 @@ def _process_data_sheet(self, row):
             if len(sheet_names) > 1:
                 LOGGER.warning(
                     "Implicitly concatenating data sheets without concat operation "
-                    "is not supported anymore. Ignoring all but the first sheet."
+                    "is deprecated and may be removed in the future."
                 )
-            data_sheet = self._get_new_data_sheet(sheet_names[0], row.data_model)
+                data_sheet = self._data_sheets_concat(sheet_names, row.data_model)
+            else:
+                data_sheet = self._get_new_data_sheet(sheet_names[0], row.data_model)
 
         else:
             if not row.new_name:

tests/test_contentindexparser.py

@@ -841,6 +841,13 @@ def test_two_fresh_sheets(self):
         )
         self.check_concat()
 
+    def test_two_fresh_sheets_implictly(self):
+        self.ci_sheet = csv_join(
+            "type,sheet_name,data_sheet,data_row_id,new_name,data_model,operation.type",
+            "data_sheet,simpleA;simpleB,,,simpledata,SimpleRowModel,",
+        )
+        self.check_concat()
+
     def test_fresh_and_existing_sheets(self):
         self.ci_sheet = csv_join(
             "type,sheet_name,data_sheet,data_row_id,new_name,data_model,operation.type",