- 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]

3 files changed, 30 insertions, 4 deletions

diff --git a/doc/build/changelog/changelog_09.rst b/doc/build/changelog/changelog_09.rst
index bc711b89a..8e5fea1a7 100644
--- a/doc/build/changelog/changelog_09.rst
+++ b/doc/build/changelog/changelog_09.rst
@@ -12,6 +12,18 @@
         :start-line: 5
 
 .. changelog::
+    :version: 0.9.3
+
+    .. change::
+        :tags: bug, orm
+        :tickets: 2935
+
+        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.
+
+.. changelog::
     :version: 0.9.2
     :released: February 2, 2014
 
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):
diff --git a/test/orm/test_composites.py b/test/orm/test_composites.py
index f13720ef3..8b777dcdf 100644
--- a/test/orm/test_composites.py
+++ b/test/orm/test_composites.py
@@ -78,6 +78,12 @@ class PointTest(fixtures.MappedTest):
         sess.commit()
         return sess
 
+    def test_early_configure(self):
+        # test [ticket:2935], that we can call a composite
+        # expression before configure_mappers()
+        Edge = self.classes.Edge
+        Edge.start.__clause_element__()
+
     def test_round_trip(self):
         Graph, Point = self.classes.Graph, self.classes.Point
 
@@ -602,6 +608,13 @@ class ManyToOneTest(fixtures.MappedTest):
         })
         mapper(B, b)
 
+    def test_early_configure(self):
+        # test [ticket:2935], that we can call a composite
+        # expression before configure_mappers()
+        A = self.classes.A
+        A.c.__clause_element__()
+
+
     def test_persist(self):
         A, C, B = (self.classes.A,
                                 self.classes.C,