- Fixed bug in baked loader system where the systemwide monkeypatch

for setting up baked lazy loaders would interfere with other
loader strategies that rely on lazy loading as a fallback, e.g.
joined and subquery eager loaders, leading to ``IndexError``
exceptions at mapper configuration time.
fixes #3612

4 files changed, 36 insertions, 2 deletions

diff --git a/doc/build/changelog/changelog_10.rst b/doc/build/changelog/changelog_10.rst
index ab261c615..b9eae73e6 100644
--- a/doc/build/changelog/changelog_10.rst
+++ b/doc/build/changelog/changelog_10.rst
@@ -19,6 +19,17 @@
     :version: 1.0.11
 
     .. change::
+        :tags: bug, ext
+        :tickets: 3612
+        :versions: 1.1.0b1
+
+        Fixed bug in baked loader system where the systemwide monkeypatch
+        for setting up baked lazy loaders would interfere with other
+        loader strategies that rely on lazy loading as a fallback, e.g.
+        joined and subquery eager loaders, leading to ``IndexError``
+        exceptions at mapper configuration time.
+
+    .. change::
         :tags: bug, orm
         :tickets: 3611
         :versions: 1.1.0b1
diff --git a/lib/sqlalchemy/ext/baked.py b/lib/sqlalchemy/ext/baked.py
index eb0c36805..d255b5ee4 100644
--- a/lib/sqlalchemy/ext/baked.py
+++ b/lib/sqlalchemy/ext/baked.py
@@ -384,7 +384,6 @@ def bake_lazy_loaders():
     Python overhead for these operations.
 
     """
-    strategies.LazyLoader._strategy_keys[:] = []
     BakedLazyLoader._strategy_keys[:] = []
 
     properties.RelationshipProperty.strategy_for(
@@ -394,6 +393,8 @@ def bake_lazy_loaders():
     properties.RelationshipProperty.strategy_for(
         lazy="baked_select")(BakedLazyLoader)
 
+    strategies.LazyLoader._strategy_keys[:] = BakedLazyLoader._strategy_keys[:]
+
 
 def unbake_lazy_loaders():
     """Disable the use of baked queries for all lazyloaders systemwide.
diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index ed8f27332..e9ad75e31 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -493,7 +493,11 @@ class StrategizedProperty(MapperProperty):
             return strategy
 
     def _get_strategy_by_cls(self, cls):
-        return self._get_strategy(cls._strategy_keys[0])
+        try:
+            return self._get_strategy(cls._strategy_keys[0])
+        except IndexError:
+            import pdb
+            pdb.set_trace()
 
     def setup(
             self, context, entity, path, adapter, **kwargs):
diff --git a/test/ext/test_baked.py b/test/ext/test_baked.py
index 740689d60..8bfa58403 100644
--- a/test/ext/test_baked.py
+++ b/test/ext/test_baked.py
@@ -717,6 +717,24 @@ class LazyLoaderTest(BakedTest):
                 u1._sa_instance_state
             )
 
+    def test_systemwide_loaders_loadable_via_lazyloader(self):
+        from sqlalchemy.orm import configure_mappers
+        from sqlalchemy.orm.strategies import LazyLoader
+
+        baked.bake_lazy_loaders()
+        try:
+            User, Address = self._o2m_fixture(lazy='joined')
+
+            configure_mappers()
+
+            is_(
+                User.addresses.property.
+                _get_strategy_by_cls(LazyLoader).__class__,
+                BakedLazyLoader
+            )
+        finally:
+            baked.unbake_lazy_loaders()
+
     def test_invocation_systemwide_loaders(self):
         baked.bake_lazy_loaders()
         try: