magic-removal: Added descriptor code for assignment of related object sets (Reporter.article_set = [a,b,c]).

git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@2510 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/related.py

@@ -94,6 +94,8 @@ class SingleRelatedObjectDescriptor(object):
         return rel_obj
         
     def __set__(self, instance, value):
+        if instance is None:
+            raise AttributeError, "%s must be accessed via instance" % self.related.opts.object_name
         # Set the value of the related field
         setattr(value, self.related.field.attname, instance)
             
@@ -126,6 +128,8 @@ class ReverseSingleRelatedObjectDescriptor(object):
             return rel_obj
 
     def __set__(self, instance, value):
+        if instance is None:
+            raise AttributeError, "%s must be accessed via instance" % self._field.name
         # Set the value of the related field
         try:
             val = getattr(value, self.field.rel.get_related_field().attname)
@@ -197,6 +201,18 @@ class ForeignRelatedObjectsDescriptor(object):
 
         return manager
 
+    def __set__(self, instance, value):
+        if instance is None:
+            raise AttributeError, "Manager must be accessed via instance"
+
+        manager = self.__get__(instance)        
+        # If the foreign key can support nulls, then completely clear the related set.
+        # Otherwise, just move the named objects into the set. 
+        if self.related.field.null:
+            manager.clear()            
+        for obj in value:
+            manager.add(obj)
+
 def _add_m2m_items(rel_manager_inst, managerclass, rel_model, join_table, source_col_name,
         target_col_name, source_pk_val, *objs):
     # Utility function used by the ManyRelatedObjectsDescriptors
@@ -329,6 +345,15 @@ class ManyRelatedObjectsDescriptor(object):
 
         return manager
 
+    def __set__(self, instance, value):
+        if instance is None:
+            raise AttributeError, "Manager must be accessed via instance"
+        
+        manager = self.__get__(instance)
+        manager.clear()
+        for obj in value:
+            manager.add(obj)
+
 class ReverseManyRelatedObjectsDescriptor(object):
     # This class provides the functionality that makes the related-object
     # managers available as attributes on a model class, for fields that have
@@ -401,6 +426,15 @@ class ReverseManyRelatedObjectsDescriptor(object):
 
         return manager
 
+    def __set__(self, instance, value):
+        if instance is None:
+            raise AttributeError, "Manager must be accessed via instance"
+            
+        manager = self.__get__(instance)
+        manager.clear()
+        for obj in value:
+            manager.add(obj)
+
 class ForeignKey(RelatedField, Field):
     empty_strings_allowed = False
     def __init__(self, to, to_field=None, **kwargs):

tests/modeltests/many_to_many/models.py

@@ -144,12 +144,19 @@ API_TESTS = """
 >>> a5.publications.all()
 []
 
-# You can clear the whole lot:
-# (put some back first)
->>> p2.article_set.add(a4, a5)
->>> a4.publications.add(p3)
+# Relation sets can be assigned. Assignment clears any existing set members
+>>> p2.article_set = [a4, a5]
+>>> p2.article_set.all()
+[NASA finds intelligent life on Earth, Oxygen-free diet works wonders]
 >>> a4.publications.all()
-[Science News, Science Weekly]
+[Science News]
+>>> a4.publications = [p3]
+>>> p2.article_set.all()
+[Oxygen-free diet works wonders]
+>>> a4.publications.all()
+[Science Weekly]
+
+# Relation sets can be cleared:
 >>> p2.article_set.clear()
 >>> p2.article_set.all()
 []
@@ -196,5 +203,4 @@ API_TESTS = """
 >>> p1.article_set.all()
 [NASA uses Python]
 
-
 """

tests/modeltests/many_to_one/models.py

@@ -83,9 +83,20 @@ John Smith
 >>> r2.article_set.all()
 []
 
-# Set the article back again.
->>> new_article2.reporter = r2
->>> new_article2.save()
+# Set the article back again using set descriptor.
+>>> r2.article_set = [new_article, new_article2]
+>>> r.article_set.all()
+[This is a test]
+>>> r2.article_set.all()
+[John's second story, Paul's story]
+
+# Funny case - assignment notation can only go so far; because the 
+# ForeignKey cannot be null, existing members of the set must remain
+>>> r.article_set = [new_article]
+>>> r.article_set.all()
+[This is a test, John's second story]
+>>> r2.article_set.all()
+[Paul's story]
 
 # Reporter cannot be null - there should not be a clear or remove method
 >>> hasattr(r2.article_set, 'remove')

tests/modeltests/many_to_one_null/models.py

@@ -49,7 +49,7 @@ Second
 1
 
 # Reporter objects have access to their related Article objects.
->>> r.article_set.order_by('headline')
+>>> r.article_set.all()
 [First, Second]
 >>> r.article_set.filter(headline__startswith='Fir')
 [First]
@@ -111,11 +111,17 @@ DoesNotExist: 'Fourth' is not related to 'John Smith'.
 >>> r2.article_set.all()
 [Fourth]
 
+# Use descriptor assignment to allocate ForeignKey. Null is legal, so
+# existing members of set that are not in the assignment set are set null
+>>> r2.article_set = [a2, a3]
+>>> r2.article_set.all()
+[Second, Third]
+
 # Clear the rest of the set
 >>> r.article_set.clear()
 >>> r.article_set.all()
 []
 >>> Article.objects.filter(reporter__isnull=True)
-[First, Second, Third]
+[First, Fourth]
 
 """