set variable scope to the outer common parent scope

nodes.py

@@ -26,7 +26,8 @@
 
 from rql import CoercionError
 from rql.base import BaseNode, Node, BinaryNode, LeafNode
-from rql.utils import function_description, quote, uquote, build_visitor_stub
+from rql.utils import (function_description, quote, uquote, build_visitor_stub,
+                       common_parent)
 
 CONSTANT_TYPES = frozenset((None, 'Date', 'Datetime', 'Boolean', 'Float', 'Int',
                             'String', 'Substitute', 'etype'))
@@ -949,11 +950,8 @@
     def set_scope(self, scopenode):
         if scopenode is self.stmt or self.stinfo['scope'] is None:
             self.stinfo['scope'] = scopenode
-        elif self.stinfo['scope'] is not self.stmt and scopenode is not self.stinfo['scope']:
-            # XXX get common parent scope if this assertion fail
-            assert scopenode.parent.scope is self.stinfo['scope'].parent.scope, \
-                   (scopenode.parent.scope, self.stinfo['scope'].parent.scope)
-            self.stinfo['scope'] = scopenode.parent.scope
+        elif not (self.stinfo['scope'] is self.stmt or scopenode is self.stinfo['scope']):
+            self.stinfo['scope'] = common_parent(self.stinfo['scope'], scopenode)
             
     def get_scope(self):
         return self.stinfo['scope']
@@ -985,6 +983,7 @@
                 return rel
         return None
 
+
 build_visitor_stub((SubQuery, And, Or, Not, Exists, Relation,
                     Comparison, MathExpression, Function, Constant,
                     VariableRef, SortTerm, ColumnAlias, Variable))

utils.py

@@ -73,6 +73,25 @@
     """Return true if the given word is a RQL keyword."""
     return word.upper() in KEYWORDS
 
+def common_parent(node1, node2):
+    """return the first common parent between node1 and node2
+
+    algorithm :
+     1) index node1's parents
+     2) climb among node2's parents until we find a common parent
+    """
+    # index node1's parents
+    node1_parents = set()
+    while node1:
+        node1_parents.add(node1)
+        node1 = node1.parent
+    # climb among node2's parents until we find a common parent
+    while node2:
+        if node2 in node1_parents:
+            return node2
+        node2 = node2.parent
+    raise Exception('DUH!')
+    
 FUNCTIONS = _GenericAdvFuncHelper.FUNCTIONS.copy()
 
 def register_function(funcdef):