project out secondary attributes from key_source tables before joining them

Author: dimitri-yatsenko

datajoint/autopopulate.py

@@ -26,15 +26,15 @@ class AutoPopulate:
     @property
     def key_source(self):
         """
-        :return: the relation whose primary key values are passed, sequentially, to the
+        :return: the query expression whose primary key values are passed, sequentially, to the
                 ``make`` method when populate() is called.
                 The default value is the join of the parent relations.
                 Users may override to change the granularity or the scope of populate() calls.
         """
         def _rename_attributes(table, props):
             return (table.proj(
                 **{attr: ref for attr, ref in props['attr_map'].items() if attr != ref})
-                if props['aliased'] else table)
+                if props['aliased'] else table.proj())
 
         if self._key_source is None:
             parents = self.target.parents(primary=True, as_objects=True, foreign_key_info=True)