- Improved the initialization logic of composite attributes such that

calling ``MyClass.attribute`` will not require that the configure
mappers step has occurred, e.g. it will just work without throwing
any error. [ticket:2935]

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/sqlalchemy/orm/descriptor_props.py b/lib/sqlalchemy/orm/descriptor_props.py
index 24b0a15e6..9ecc9bb62 100644
--- a/lib/sqlalchemy/orm/descriptor_props.py
+++ b/lib/sqlalchemy/orm/descriptor_props.py
@@ -165,7 +165,6 @@ class CompositeProperty(DescriptorProperty):
         has been associated with its parent mapper.
 
         """
-        self._init_props()
         self._setup_arguments_on_columns()
 
     def _create_descriptor(self):
@@ -236,11 +235,12 @@ class CompositeProperty(DescriptorProperty):
             for prop in self.props
         ]
 
-    def _init_props(self):
-        self.props = props = []
+    @util.memoized_property
+    def props(self):
+        props = []
         for attr in self.attrs:
             if isinstance(attr, str):
-                prop = self.parent.get_property(attr)
+                prop = self.parent.get_property(attr, _configure_mappers=False)
             elif isinstance(attr, schema.Column):
                 prop = self.parent._columntoproperty[attr]
             elif isinstance(attr, attributes.InstrumentedAttribute):
@@ -251,6 +251,7 @@ class CompositeProperty(DescriptorProperty):
                         "attributes/attribute names as arguments, got: %r"
                         % (attr,))
             props.append(prop)
+        return props
 
     @property
     def columns(self):