From 60c3e55b1f7c87ef9fa7c5ffdaf6e8dba5ab7043 Mon Sep 17 00:00:00 2001
From: Luke Plant <L.Plant.98@cantab.net>
Date: Fri, 26 May 2006 23:41:43 +0000
Subject: [PATCH] Fixed bug with QuerySet.exclude() failing to do negations on
 Q objects, and at the same time generalised exclude/QNot so that they work
 for 'external' Q objects i.e. ones that simply have 'get_sql' defined.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2997 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/db/models/query.py             | 19 +++++++++++++------
 tests/modeltests/or_lookups/models.py |  4 ++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 1107269235..91ae294a62 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -291,22 +291,26 @@ class QuerySet(object):
 
     def filter(self, *args, **kwargs):
         "Returns a new QuerySet instance with the args ANDed to the existing set."
-        return self._filter_or_exclude(Q, *args, **kwargs)
+        return self._filter_or_exclude(None, *args, **kwargs)
 
     def exclude(self, *args, **kwargs):
         "Returns a new QuerySet instance with NOT (args) ANDed to the existing set."
         return self._filter_or_exclude(QNot, *args, **kwargs)
 
-    def _filter_or_exclude(self, qtype, *args, **kwargs):
+    def _filter_or_exclude(self, mapper, *args, **kwargs):
+        # mapper is a callable used to transform Q objects,
+        # or None for identity transform
+        if mapper is None:
+            mapper = lambda x: x
         if len(args) > 0 or len(kwargs) > 0:
             assert self._limit is None and self._offset is None, \
                 "Cannot filter a query once a slice has been taken."
 
         clone = self._clone()
         if len(kwargs) > 0:
-            clone._filters = clone._filters & qtype(**kwargs)
+            clone._filters = clone._filters & mapper(Q(**kwargs))
         if len(args) > 0:
-            clone._filters = clone._filters & reduce(operator.and_, args)
+            clone._filters = clone._filters & reduce(operator.and_, map(mapper, args))
         return clone
 
     def complex_filter(self, filter_obj):
@@ -318,7 +322,7 @@ class QuerySet(object):
         if hasattr(filter_obj, 'get_sql'):
             return self._filter_or_exclude(None, filter_obj)
         else:
-            return self._filter_or_exclude(Q, **filter_obj)
+            return self._filter_or_exclude(None, **filter_obj)
 
     def select_related(self, true_or_false=True):
         "Returns a new QuerySet instance with '_select_related' modified."
@@ -582,9 +586,12 @@ class Q(object):
 
 class QNot(Q):
     "Encapsulates NOT (...) queries as objects"
+    def __init__(self, q):
+        "Creates a negation of the q object passed in."
+        self.q = q
 
     def get_sql(self, opts):
-        tables, joins, where, params = super(QNot, self).get_sql(opts)
+        tables, joins, where, params = self.q.get_sql(opts)
         where2 = ['(NOT (%s))' % " AND ".join(where)]
         return tables, joins, where2, params
 
diff --git a/tests/modeltests/or_lookups/models.py b/tests/modeltests/or_lookups/models.py
index a07dacdd5a..ef4d4dc5ca 100644
--- a/tests/modeltests/or_lookups/models.py
+++ b/tests/modeltests/or_lookups/models.py
@@ -89,6 +89,10 @@ Hello and goodbye
 >>> Article.objects.filter(Q(headline__startswith='Hello')).in_bulk([1,2])
 {1: Hello}
 
+# Demonstrating exclude with a Q object
+>>> Article.objects.exclude(Q(headline__startswith='Hello'))
+[Goodbye]
+
 # The 'complex_filter' method supports framework features such as 
 # 'limit_choices_to' which normally take a single dictionary of lookup arguments
 # but need to support arbitrary queries via Q objects too.