foo.diff

commit 82b4162aebdf319bcc39af342ebee94be8c8eebd
Author: Loic Bistuer <loic.bistuer@gmail.com>
Date:   Wed Jan 28 03:12:24 2015 +0700

    WIP

diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index d917b01..d5bc763 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -806,7 +806,7 @@ class ForeignRelatedObjectsDescriptor(object):
     # some other model. In the example "poll.choice_set", the choice_set
     # attribute is a ForeignRelatedObjectsDescriptor instance.
     def __init__(self, related):
-        self.related = related   # RelatedObject instance
+        self.related = related
 
     def __get__(self, instance, instance_type=None):
         if instance is None:
@@ -839,38 +839,51 @@ class ForeignRelatedObjectsDescriptor(object):
         )
 
 
-def create_many_related_manager(superclass, rel):
-    """Creates a manager that subclasses 'superclass' (which is a Manager)
-    and adds behavior for many-to-many related objects."""
+def create_many_related_manager(superclass, rel, reverse):
+    """
+    Creates a manager that subclasses 'superclass' (which is a Manager)
+    and adds behavior for many-to-many related objects.
+    """
+
     class ManyRelatedManager(superclass):
-        def __init__(self, model=None, query_field_name=None, instance=None, symmetrical=None,
-                     source_field_name=None, target_field_name=None, reverse=False,
-                     through=None, prefetch_cache_name=None):
+
+        def __init__(self, instance=None):
             super(ManyRelatedManager, self).__init__()
-            self.model = model
-            self.query_field_name = query_field_name
 
-            source_field = through._meta.get_field(source_field_name)
-            source_related_fields = source_field.related_fields
+            self.instance = instance
 
-            self.core_filters = {}
-            for lh_field, rh_field in source_related_fields:
-                self.core_filters['%s__%s' % (query_field_name, rh_field.name)] = getattr(instance, rh_field.attname)
+            if not reverse:
+                self.model = rel.to
+                self.query_field_name = rel.field.related_query_name()
+                self.prefetch_cache_name = rel.field.name
+                self.source_field_name = rel.field.m2m_field_name()
+                self.target_field_name = rel.field.m2m_reverse_field_name()
+                self.symmetrical = rel.symmetrical
 
-            self.instance = instance
-            self.symmetrical = symmetrical
-            self.source_field = source_field
-            self.target_field = through._meta.get_field(target_field_name)
-            self.source_field_name = source_field_name
-            self.target_field_name = target_field_name
+            else:
+                self.model = rel.related_model
+                self.query_field_name = rel.field.name
+                self.prefetch_cache_name = rel.field.related_query_name()
+                self.source_field_name = rel.field.m2m_reverse_field_name()
+                self.target_field_name = rel.field.m2m_field_name()
+                self.symmetrical=False
+
+            self.through = rel.through
             self.reverse = reverse
-            self.through = through
-            self.prefetch_cache_name = prefetch_cache_name
-            self.related_val = source_field.get_foreign_related_value(instance)
+
+            self.source_field = self.through._meta.get_field(self.source_field_name)
+            self.target_field = self.through._meta.get_field(self.target_field_name)
+
+            self.core_filters = {}
+            for lh_field, rh_field in self.source_field.related_fields:
+                self.core_filters['%s__%s' % (self.query_field_name, rh_field.name)] = getattr(instance, rh_field.attname)
+
+            self.related_val = self.source_field.get_foreign_related_value(instance)
             if None in self.related_val:
                 raise ValueError('"%r" needs to have a value for field "%s" before '
                                  'this many-to-many relationship can be used.' %
-                                 (instance, source_field_name))
+                                 (instance, self.source_field_name))
+
             # Even if this relation is not to pk, we require still pk value.
             # The wish is that the instance has been already saved to DB,
             # although having a pk value isn't a guarantee of that.
@@ -883,18 +896,8 @@ def create_many_related_manager(superclass, rel):
             # We use **kwargs rather than a kwarg argument to enforce the
             # `manager='manager_name'` syntax.
             manager = getattr(self.model, kwargs.pop('manager'))
-            manager_class = create_many_related_manager(manager.__class__, rel)
-            return manager_class(
-                model=self.model,
-                query_field_name=self.query_field_name,
-                instance=self.instance,
-                symmetrical=self.symmetrical,
-                source_field_name=self.source_field_name,
-                target_field_name=self.target_field_name,
-                reverse=self.reverse,
-                through=self.through,
-                prefetch_cache_name=self.prefetch_cache_name,
-            )
+            manager_class = create_many_related_manager(manager.__class__, rel, self.reverse)
+            return manager_class(instance=self.instance)
         do_not_call_in_templates = True
 
         def _build_remove_filters(self, removed_vals):
@@ -959,7 +962,7 @@ def create_many_related_manager(superclass, rel):
             )
 
         def add(self, *objs):
-            if not rel.through._meta.auto_created:
+            if not self.through._meta.auto_created:
                 opts = self.through._meta
                 raise AttributeError(
                     "Cannot use add() on a ManyToManyField which specifies an "
@@ -977,7 +980,7 @@ def create_many_related_manager(superclass, rel):
         add.alters_data = True
 
         def remove(self, *objs):
-            if not rel.through._meta.auto_created:
+            if not self.through._meta.auto_created:
                 opts = self.through._meta
                 raise AttributeError(
                     "Cannot use remove() on a ManyToManyField which specifies "
@@ -1144,111 +1147,36 @@ def create_many_related_manager(superclass, rel):
 class ManyRelatedObjectsDescriptor(object):
     # This class provides the functionality that makes the related-object
     # managers available as attributes on a model class, for fields that have
-    # multiple "remote" values and have a ManyToManyField pointed at them by
-    # some other model (rather than having a ManyToManyField themselves).
-    # In the example "publication.article_set", the article_set attribute is a
-    # ManyRelatedObjectsDescriptor instance.
-    def __init__(self, related):
-        self.related = related   # RelatedObject instance
-
-    @cached_property
-    def related_manager_cls(self):
-        # Dynamically create a class that subclasses the related
-        # model's default manager.
-        return create_many_related_manager(
-            self.related.related_model._default_manager.__class__,
-            self.related.field.rel
-        )
-
-    def __get__(self, instance, instance_type=None):
-        if instance is None:
-            return self
-
-        rel_model = self.related.related_model
-
-        manager = self.related_manager_cls(
-            model=rel_model,
-            query_field_name=self.related.field.name,
-            prefetch_cache_name=self.related.field.related_query_name(),
-            instance=instance,
-            symmetrical=False,
-            source_field_name=self.related.field.m2m_reverse_field_name(),
-            target_field_name=self.related.field.m2m_field_name(),
-            reverse=True,
-            through=self.related.field.rel.through,
-        )
-
-        return manager
-
-    def __set__(self, instance, value):
-        if not self.related.field.rel.through._meta.auto_created:
-            opts = self.related.field.rel.through._meta
-            raise AttributeError(
-                "Cannot set values on a ManyToManyField which specifies an "
-                "intermediary model. Use %s.%s's Manager instead." % (opts.app_label, opts.object_name)
-            )
-
-        # Force evaluation of `value` in case it's a queryset whose
-        # value could be affected by `manager.clear()`. Refs #19816.
-        value = tuple(value)
-
-        manager = self.__get__(instance)
-        db = router.db_for_write(manager.through, instance=manager.instance)
-        with transaction.atomic(using=db, savepoint=False):
-            manager.clear()
-            manager.add(*value)
-
-
-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
-    # multiple "remote" values and have a ManyToManyField defined in their
-    # model (rather than having another model pointed *at* them).
-    # In the example "article.publications", the publications attribute is a
-    # ReverseManyRelatedObjectsDescriptor instance.
-    def __init__(self, m2m_field):
-        self.field = m2m_field
+    # multiple "remote" values
+    def __init__(self, rel, reverse=False):
+        self.rel = rel
+        self.reverse = reverse
 
     @property
     def through(self):
-        # through is provided so that you have easy access to the through
+        # This is provided so that you have easy access to the through
         # model (Book.authors.through) for inlines, etc. This is done as
         # a property to ensure that the fully resolved value is returned.
-        return self.field.rel.through
+        return self.rel.through
 
     @cached_property
     def related_manager_cls(self):
-        # Dynamically create a class that subclasses the related model's
-        # default manager.
-        return create_many_related_manager(
-            self.field.rel.to._default_manager.__class__,
-            self.field.rel
-        )
+        # Dynamically create a class that subclasses the related
+        # model's default manager.
+        model = self.rel.related_model if self.reverse else self.rel.to
+        return create_many_related_manager(model._default_manager.__class__, self.rel, self.reverse)
 
     def __get__(self, instance, instance_type=None):
         if instance is None:
             return self
-
-        manager = self.related_manager_cls(
-            model=self.field.rel.to,
-            query_field_name=self.field.related_query_name(),
-            prefetch_cache_name=self.field.name,
-            instance=instance,
-            symmetrical=self.field.rel.symmetrical,
-            source_field_name=self.field.m2m_field_name(),
-            target_field_name=self.field.m2m_reverse_field_name(),
-            reverse=False,
-            through=self.field.rel.through,
-        )
-
-        return manager
+        return self.related_manager_cls(instance=instance)
 
     def __set__(self, instance, value):
-        if not self.field.rel.through._meta.auto_created:
-            opts = self.field.rel.through._meta
+        if not self.rel.through._meta.auto_created:
+            opts = self.rel.through._meta
             raise AttributeError(
                 "Cannot set values on a ManyToManyField which specifies an "
-                "intermediary model.  Use %s.%s's Manager instead." % (opts.app_label, opts.object_name)
+                "intermediary model. Use %s.%s's Manager instead." % (opts.app_label, opts.object_name)
             )
 
         # Force evaluation of `value` in case it's a queryset whose
@@ -1474,10 +1402,6 @@ class ManyToManyRel(ForeignObjectRel):
         self.symmetrical = symmetrical
         self.db_constraint = db_constraint
 
-    def is_hidden(self):
-        "Should the related object be hidden?"
-        return self.related_name is not None and self.related_name[-1] == '+'
-
     def get_related_field(self):
         """
         Returns the field in the 'to' object to which this relationship is tied.
@@ -2567,7 +2491,7 @@ class ManyToManyField(RelatedField):
             self.rel.through = create_many_to_many_intermediary_model(self, cls)
 
         # Add the descriptor for the m2m relation
-        setattr(cls, self.name, ReverseManyRelatedObjectsDescriptor(self))
+        setattr(cls, self.name, ManyRelatedObjectsDescriptor(self.rel))
 
         # Set up the accessor for the m2m table name for the relation
         self.m2m_db_table = curry(self._get_m2m_db_table, cls._meta)
@@ -2583,7 +2507,7 @@ class ManyToManyField(RelatedField):
         # Internal M2Ms (i.e., those with a related name ending with '+')
         # and swapped models don't get a related descriptor.
         if not self.rel.is_hidden() and not related.related_model._meta.swapped:
-            setattr(cls, related.get_accessor_name(), ManyRelatedObjectsDescriptor(related))
+            setattr(cls, related.get_accessor_name(), ManyRelatedObjectsDescriptor(related, reverse=True))
 
         # Set up the accessors for the column names on the m2m table
         self.m2m_column_name = curry(self._get_m2m_attr, related, 'column')
diff --git a/tests/many_to_many/tests.py b/tests/many_to_many/tests.py
index adb8978..8626a44 100644
--- a/tests/many_to_many/tests.py
+++ b/tests/many_to_many/tests.py
@@ -385,7 +385,7 @@ class ManyToManyTests(TestCase):
     def test_reverse_assign_with_queryset(self):
         # Ensure that querysets used in M2M assignments are pre-evaluated
         # so their value isn't affected by the clearing operation in
-        # ReverseManyRelatedObjectsDescriptor.__set__. Refs #19816.
+        # ManyRelatedObjectsDescriptor.__set__. Refs #19816.
         self.p1.article_set = [self.a1, self.a2]
 
         qs = self.p1.article_set.filter(headline='Django lets you build Web apps easily')
diff --git a/tests/schema/fields.py b/tests/schema/fields.py
index 4f70c96..6e58069 100644
--- a/tests/schema/fields.py
+++ b/tests/schema/fields.py
@@ -1,9 +1,10 @@
 from django.db.models.fields.related import (
     create_many_to_many_intermediary_model,
     ManyToManyField, ManyToManyRel, RelatedField,
-    RECURSIVE_RELATIONSHIP_CONSTANT, ReverseManyRelatedObjectsDescriptor,
+    RECURSIVE_RELATIONSHIP_CONSTANT, ManyRelatedObjectsDescriptor,
 )
 
+
 from django.utils.functional import curry
 
 
@@ -41,7 +42,7 @@ class CustomManyToManyField(RelatedField):
         super(CustomManyToManyField, self).contribute_to_class(cls, name, **kwargs)
         if not self.rel.through and not cls._meta.abstract and not cls._meta.swapped:
             self.rel.through = create_many_to_many_intermediary_model(self, cls)
-        setattr(cls, self.name, ReverseManyRelatedObjectsDescriptor(self))
+        setattr(cls, self.name, ManyRelatedObjectsDescriptor(self))
         self.m2m_db_table = curry(self._get_m2m_db_table, cls._meta)
 
     def get_internal_type(self):