Fixing issue with two-way referenced relations in the sqlalchemy interface (closes issue #13)

configdb/db/interface/sa_generator.py

@@ -8,6 +8,7 @@ class SqlAlchemyGenerator(object):
 
     def __init__(self, schema_obj):
         self.schema = schema_obj
+        self.defined_relations = []
 
     def _audit_table_def(self):
         return """
@@ -76,6 +77,13 @@ class %(class_name)s(Base):
             field.name, ', '.join(args))
 
     def _sa_field_relation_def(self, entity, field):
+        assoc_table = self._sa_assoc_table_name(field)
+        if assoc_table in self.defined_relations:
+            # In this case, we don't need a backref (it already exists)
+            return '%s = relationship("%s", secondary=%s)' % (
+                field.name,
+                field.remote_name.capitalize(),
+                assoc_table + '_table')
         return '%s = relationship("%s", secondary=%s, backref="%s")' % (
             field.name,
             field.remote_name.capitalize(),
@@ -83,12 +91,17 @@ class %(class_name)s(Base):
             pl.plural(entity.name))
 
     def _sa_field_assoc_table_def(self, entity, field):
+        table_name = self._sa_assoc_table_name(field)
+        if table_name in self.defined_relations:
+            #we have a 2-way used relation, and do not want to re-define it
+            return ""
+        self.defined_relations.append(table_name)
         return """
 %s_table = Table('%s', Base.metadata,
     Column('left_id', Integer, ForeignKey('%s.id')),
     Column('right_id', Integer, ForeignKey('%s.id')))""" % (
-            self._sa_assoc_table_name(field),
-            self._sa_assoc_table_name(field),
+            table_name,
+            table_name,
             field.local_name,
             field.remote_name)
 
@@ -106,4 +119,3 @@ class %(class_name)s(Base):
             out.append(self._sa_entity_aux_tables(ent))
             out.append(self._sa_entity_def(ent))
         return '\n'.join(out)
-