- Added new event handlers :meth:`.AttributeEvents.init_collection`

and :meth:`.AttributeEvents.dispose_collection`, which track when
a collection is first associated with an instance and when it is
replaced.  These handlers supersede the :meth:`.collection.linker`
annotation. The old hook remains supported through an event adapter.

1 files changed, 20 insertions, 3 deletions

diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index 66197ba0e..459a52539 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -863,6 +863,16 @@ class CollectionAttributeImpl(AttributeImpl):
         self.copy = copy_function
         self.collection_factory = typecallable
 
+        if hasattr(self.collection_factory, "_sa_linker"):
+
+            @event.listens_for(self, "init_collection")
+            def link(target, collection, collection_adapter):
+                collection._sa_linker(collection_adapter)
+
+            @event.listens_for(self, "dispose_collection")
+            def unlink(target, collection, collection_adapter):
+                collection._sa_linker(None)
+
     def __copy(self, item):
         return [y for y in collections.collection_adapter(item)]
 
@@ -955,9 +965,14 @@ class CollectionAttributeImpl(AttributeImpl):
         return user_data
 
     def _initialize_collection(self, state):
-        return state.manager.initialize_collection(
+
+        adapter, collection = state.manager.initialize_collection(
             self.key, state, self.collection_factory)
 
+        self.dispatch.init_collection(state, collection, adapter)
+
+        return adapter, collection
+
     def append(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
         collection = self.get_collection(state, dict_, passive=passive)
         if collection is PASSIVE_NO_RESULT:
@@ -1026,12 +1041,14 @@ class CollectionAttributeImpl(AttributeImpl):
         # place a copy of "old" in state.committed_state
         state._modified_event(dict_, self, old, True)
 
-        old_collection = getattr(old, '_sa_adapter')
+        old_collection = old._sa_adapter
 
         dict_[self.key] = user_data
 
         collections.bulk_replace(new_values, old_collection, new_collection)
-        old_collection.unlink(old)
+
+        del old._sa_adapter
+        self.dispatch.dispose_collection(state, old, old_collection)
 
     def _invalidate_collection(self, collection):
         adapter = getattr(collection, '_sa_adapter')