Issue a warning when a declarative detects a likely trailing comma: foo = Column(foo),

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/sqlalchemy/ext/declarative.py b/lib/sqlalchemy/ext/declarative.py
index 4feb47456..41a51c8c6 100644
--- a/lib/sqlalchemy/ext/declarative.py
+++ b/lib/sqlalchemy/ext/declarative.py
@@ -159,6 +159,12 @@ class DeclarativeMeta(type):
         our_stuff = {}
         for k in dict_:
             value = dict_[k]
+            if (isinstance(value, tuple) and len(value) == 1 and
+                isinstance(value[0], (Column, MapperProperty))):
+                util.warn("Ignoring declarative-like tuple value of attribute "
+                          "%s: possibly a copy-and-paste error with a comma "
+                          "left at the end of the line?" % k)
+                continue
             if not isinstance(value, (Column, MapperProperty)):
                 continue
             prop = _deferred_relation(cls, value)