loader strategy regression fixes

Fixed regression where using :func:`_orm.selectinload` and
:func:`_orm.subqueryload` to load a two-level-deep path would lead to an
attribute error.

Fixed regression where using the :func:`_orm.noload` loader strategy in
conjunction with a "dynamic" relationship would lead to an attribute error
as the noload strategy would attempt to apply itself to the dynamic loader.

Fixes: #6419
Fixes: #6420
Change-Id: I933b208f16a9723f6ebeab7addbe118903a1f8f5

1 files changed, 24 insertions, 2 deletions

diff --git a/lib/sqlalchemy/orm/dynamic.py b/lib/sqlalchemy/orm/dynamic.py
index bf8fc0e33..a4b5f58c7 100644
--- a/lib/sqlalchemy/orm/dynamic.py
+++ b/lib/sqlalchemy/orm/dynamic.py
@@ -105,10 +105,11 @@ class DynamicAttributeImpl(attributes.AttributeImpl):
         passive=attributes.PASSIVE_NO_INITIALIZE,
     ):
         if not passive & attributes.SQL_OK:
-            return self._get_collection_history(state, passive).added_items
+            data = self._get_collection_history(state, passive).added_items
         else:
             history = self._get_collection_history(state, passive)
-            return history.added_plus_unchanged
+            data = history.added_plus_unchanged
+        return DynamicCollectionAdapter(data)
 
     @util.memoized_property
     def _append_token(self):
@@ -259,6 +260,27 @@ class DynamicAttributeImpl(attributes.AttributeImpl):
         self.remove(state, dict_, value, initiator, passive=passive)
 
 
+class DynamicCollectionAdapter(object):
+    """simplified CollectionAdapter for internal API consistency"""
+
+    def __init__(self, data):
+        self.data = data
+
+    def __iter__(self):
+        return iter(self.data)
+
+    def _reset_empty(self):
+        pass
+
+    def __len__(self):
+        return len(self.data)
+
+    def __bool__(self):
+        return True
+
+    __nonzero__ = __bool__
+
+
 class AppenderMixin(object):
     query_class = None