From f244287f46476f3b111a2495ce4207530f4b51d8 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 12 Dec 2013 13:30:16 -0500
Subject: [PATCH] - :func:`.composite` will raise an informative error message
 when the columns/attribute (names) passed don't resolve to a Column or mapped
 attribute (such as an erroneous tuple); previously raised an unbound local.
 [ticket:2889]

---
 doc/build/changelog/changelog_08.rst   | 10 ++++++++++
 lib/sqlalchemy/orm/descriptor_props.py |  5 +++++
 test/orm/test_composites.py            | 20 +++++++++++++++++++-
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/doc/build/changelog/changelog_08.rst b/doc/build/changelog/changelog_08.rst
index 2cd9b58554..2e1bdc9ad6 100644
--- a/doc/build/changelog/changelog_08.rst
+++ b/doc/build/changelog/changelog_08.rst
@@ -11,6 +11,16 @@
 .. changelog::
     :version: 0.8.5
 
+    .. change::
+        :tags: bug, orm
+        :versions: 0.9.0b2
+        :tickets: 2889
+
+        :func:`.composite` will raise an informative error message when the
+        columns/attribute (names) passed don't resolve to a Column or mapped
+        attribute (such as an erroneous tuple); previously raised an unbound
+        local.
+
     .. change::
         :tags: bug, declarative
         :versions: 0.9.0b2
diff --git a/lib/sqlalchemy/orm/descriptor_props.py b/lib/sqlalchemy/orm/descriptor_props.py
index 1156a140e9..231e531e43 100644
--- a/lib/sqlalchemy/orm/descriptor_props.py
+++ b/lib/sqlalchemy/orm/descriptor_props.py
@@ -245,6 +245,11 @@ class CompositeProperty(DescriptorProperty):
                 prop = self.parent._columntoproperty[attr]
             elif isinstance(attr, attributes.InstrumentedAttribute):
                 prop = attr.property
+            else:
+                raise sa_exc.ArgumentError(
+                        "Composite expects Column or Column-bound "
+                        "attributes/attribute names as arguments, got: %r"
+                        % (attr,))
             props.append(prop)
 
     @property
diff --git a/test/orm/test_composites.py b/test/orm/test_composites.py
index b4abb2dcee..8946b6908d 100644
--- a/test/orm/test_composites.py
+++ b/test/orm/test_composites.py
@@ -6,7 +6,7 @@ from sqlalchemy import Integer, String, ForeignKey, \
 from sqlalchemy.testing.schema import Table, Column
 from sqlalchemy.orm import mapper, relationship, \
     CompositeProperty, aliased
-from sqlalchemy.orm import composite, Session
+from sqlalchemy.orm import composite, Session, configure_mappers
 from sqlalchemy.testing import eq_
 from sqlalchemy.testing import fixtures
 
@@ -739,6 +739,24 @@ class ConfigurationTest(fixtures.MappedTest):
         })
         self._test_roundtrip()
 
+    def test_check_prop_type(self):
+        edge, Edge, Point = (self.tables.edge,
+                                self.classes.Edge,
+                                self.classes.Point)
+        mapper(Edge, edge, properties={
+            'start': sa.orm.composite(Point, (edge.c.x1,), edge.c.y1),
+        })
+        assert_raises_message(
+            sa.exc.ArgumentError,
+            # note that we also are checking that the tuple
+            # renders here, so the "%" operator in the string needs to
+            # apply the tuple also
+            r"Composite expects Column or Column-bound "
+            "attributes/attribute names as "
+            "arguments, got: \(Column",
+            configure_mappers
+        )
+
 class ComparatorTest(fixtures.MappedTest, testing.AssertsCompiledSQL):
     __dialect__ = 'default'
 
-- 
2.47.3