Merge "Handle association proxy delete and provide for scalar delete cascade"

2 files changed, 32 insertions, 6 deletions

diff --git a/lib/sqlalchemy/ext/associationproxy.py b/lib/sqlalchemy/ext/associationproxy.py
index a0945fa6c..3c27cb59f 100644
--- a/lib/sqlalchemy/ext/associationproxy.py
+++ b/lib/sqlalchemy/ext/associationproxy.py
@@ -94,7 +94,8 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
 
     def __init__(self, target_collection, attr, creator=None,
                  getset_factory=None, proxy_factory=None,
-                 proxy_bulk_set=None, info=None):
+                 proxy_bulk_set=None, info=None,
+                 cascade_scalar_deletes=False):
         """Construct a new :class:`.AssociationProxy`.
 
         The :func:`.association_proxy` function is provided as the usual
@@ -119,6 +120,15 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
           If you want to construct instances differently, supply a 'creator'
           function that takes arguments as above and returns instances.
 
+        :param cascade_scalar_deletes: when True, indicates that setting
+         the proxied value to ``None``, or deleting it via ``del``, should
+         also remove the source object.  Only applies to scalar attributes.
+         Normally, removing the proxied target will not remove the proxy
+         source, as this object may have other state that is still to be
+         kept.
+
+         .. versionadded:: 1.3
+
         :param getset_factory: Optional.  Proxied attribute access is
           automatically handled by routines that get and set values based on
           the `attr` argument for this proxy.
@@ -150,6 +160,7 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
         self.getset_factory = getset_factory
         self.proxy_factory = proxy_factory
         self.proxy_bulk_set = proxy_bulk_set
+        self.cascade_scalar_deletes = cascade_scalar_deletes
 
         self.owning_class = None
         self.key = '_%s_%s_%s' % (
@@ -308,9 +319,13 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
             creator = self.creator and self.creator or self.target_class
             target = getattr(obj, self.target_collection)
             if target is None:
+                if values is None:
+                    return
                 setattr(obj, self.target_collection, creator(values))
             else:
                 self._scalar_set(target, values)
+                if values is None and self.cascade_scalar_deletes:
+                    setattr(obj, self.target_collection, None)
         else:
             proxy = self.__get__(obj, None)
             if proxy is not values:
@@ -321,7 +336,11 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
         if self.owning_class is None:
             self._calc_owner(obj, None)
 
-        delattr(obj, self.key)
+        if self.scalar:
+            target = getattr(obj, self.target_collection)
+            if target is not None:
+                delattr(target, self.value_attr)
+        delattr(obj, self.target_collection)
 
     def _initialize_scalar_accessors(self):
         if self.getset_factory:
diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index e9227362e..0bbe70655 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -673,7 +673,6 @@ class ScalarAttributeImpl(AttributeImpl):
 
     def delete(self, state, dict_):
 
-        # TODO: catch key errors, convert to attributeerror?
         if self.dispatch._active_history:
             old = self.get(state, dict_, PASSIVE_RETURN_NEVER_SET)
         else:
@@ -682,7 +681,10 @@ class ScalarAttributeImpl(AttributeImpl):
         if self.dispatch.remove:
             self.fire_remove_event(state, dict_, old, self._remove_token)
         state._modified_event(dict_, self, old)
-        del dict_[self.key]
+        try:
+            del dict_[self.key]
+        except KeyError:
+            raise AttributeError("%s object does not have a value" % self)
 
     def get_history(self, state, dict_, passive=PASSIVE_OFF):
         if self.key in dict_:
@@ -742,7 +744,10 @@ class ScalarObjectAttributeImpl(ScalarAttributeImpl):
     def delete(self, state, dict_):
         old = self.get(state, dict_)
         self.fire_remove_event(state, dict_, old, self._remove_token)
-        del dict_[self.key]
+        try:
+            del dict_[self.key]
+        except:
+            raise AttributeError("%s object does not have a value" % self)
 
     def get_history(self, state, dict_, passive=PASSIVE_OFF):
         if self.key in dict_:
@@ -969,7 +974,9 @@ class CollectionAttributeImpl(AttributeImpl):
 
         collection = self.get_collection(state, state.dict)
         collection.clear_with_event()
-        # TODO: catch key errors, convert to attributeerror?
+
+        # key is always present because we checked above.  e.g.
+        # del is a no-op if collection not present.
         del dict_[self.key]
 
     def initialize(self, state, dict_):