--- a/app/django/utils/tree.py Tue Oct 14 12:36:55 2008 +0000
+++ b/app/django/utils/tree.py Tue Oct 14 16:00:59 2008 +0000
@@ -29,6 +29,22 @@
self.subtree_parents = []
self.negated = negated
+ # We need this because of django.db.models.query_utils.Q. Q. __init__() is
+ # problematic, but it is a natural Node subclass in all other respects.
+ def _new_instance(cls, children=None, connector=None, negated=False):
+ """
+ This is called to create a new instance of this class when we need new
+ Nodes (or subclasses) in the internal code in this class. Normally, it
+ just shadows __init__(). However, subclasses with an __init__ signature
+ that is not an extension of Node.__init__ might need to implement this
+ method to allow a Node to create a new instance of them (if they have
+ any extra setting up to do).
+ """
+ obj = Node(children, connector, negated)
+ obj.__class__ = cls
+ return obj
+ _new_instance = classmethod(_new_instance)
+
def __str__(self):
if self.negated:
return '(NOT (%s: %s))' % (self.connector, ', '.join([str(c) for c
@@ -71,7 +87,7 @@
Otherwise, the whole tree is pushed down one level and a new root
connector is created, connecting the existing tree and the new node.
"""
- if node in self.children:
+ if node in self.children and conn_type == self.connector:
return
if len(self.children) < 2:
self.connector = conn_type
@@ -82,7 +98,8 @@
else:
self.children.append(node)
else:
- obj = Node(self.children, self.connector, self.negated)
+ obj = self._new_instance(self.children, self.connector,
+ self.negated)
self.connector = conn_type
self.children = [obj, node]
@@ -96,7 +113,8 @@
Interpreting the meaning of this negate is up to client code. This
method is useful for implementing "not" arrangements.
"""
- self.children = [Node(self.children, self.connector, not self.negated)]
+ self.children = [self._new_instance(self.children, self.connector,
+ not self.negated)]
self.connector = self.default
def start_subtree(self, conn_type):
@@ -108,12 +126,13 @@
if len(self.children) == 1:
self.connector = conn_type
elif self.connector != conn_type:
- self.children = [Node(self.children, self.connector, self.negated)]
+ self.children = [self._new_instance(self.children, self.connector,
+ self.negated)]
self.connector = conn_type
self.negated = False
- self.subtree_parents.append(Node(self.children, self.connector,
- self.negated))
+ self.subtree_parents.append(self.__class__(self.children,
+ self.connector, self.negated))
self.connector = self.default
self.negated = False
self.children = []
@@ -126,7 +145,7 @@
the current instances state to be the parent.
"""
obj = self.subtree_parents.pop()
- node = Node(self.children, self.connector)
+ node = self.__class__(self.children, self.connector)
self.connector = obj.connector
self.negated = obj.negated
self.children = obj.children