Warn for lower-case column attribute on declarative

A warning is emitted in the case that a :func:`.column` object is applied to
a declarative class, as it seems likely this intended to be a
:class:`.Column` object.

Fixes: #4374
Change-Id: I2e617ef65547162e3ba6587c168548ad0cf6203d

1 files changed, 57 insertions, 0 deletions

diff --git a/test/ext/declarative/test_basic.py b/test/ext/declarative/test_basic.py
index d2dc1a425..e8a9a140c 100644
--- a/test/ext/declarative/test_basic.py
+++ b/test/ext/declarative/test_basic.py
@@ -1,6 +1,7 @@
 
 from sqlalchemy.testing import eq_, assert_raises, \
     assert_raises_message, expect_warnings, is_
+from sqlalchemy.testing import assertions
 from sqlalchemy.ext import declarative as decl
 from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy import exc
@@ -175,6 +176,62 @@ class DeclarativeTest(DeclarativeTestBase):
         assert class_mapper(Bar).get_property('some_data').columns[0] \
             is t.c.data
 
+    def test_lower_case_c_column_warning(self):
+        with assertions.expect_warnings(
+            r"Attribute 'x' on class <class .*Foo.* appears to be a "
+            r"non-schema 'sqlalchemy.sql.column\(\)' object; ",
+        ):
+            class Foo(Base):
+                __tablename__ = 'foo'
+
+                id = Column(Integer, primary_key=True)
+                x = sa.sql.expression.column(Integer)
+                y = Column(Integer)
+
+        class MyMixin(object):
+            x = sa.sql.expression.column(Integer)
+            y = Column(Integer)
+
+        with assertions.expect_warnings(
+            r"Attribute 'x' on class <class .*MyMixin.* appears to be a "
+            r"non-schema 'sqlalchemy.sql.column\(\)' object; ",
+        ):
+            class Foo2(MyMixin, Base):
+                __tablename__ = 'foo2'
+
+                id = Column(Integer, primary_key=True)
+
+        with assertions.expect_warnings(
+            r"Attribute 'x' on class <class .*Foo3.* appears to be a "
+            r"non-schema 'sqlalchemy.sql.column\(\)' object; ",
+        ):
+            class Foo3(Base):
+                __tablename__ = 'foo3'
+
+                id = Column(Integer, primary_key=True)
+
+                @declared_attr
+                def x(cls):
+                    return sa.sql.expression.column(Integer)
+
+                y = Column(Integer)
+
+        with assertions.expect_warnings(
+            r"Attribute 'x' on class <class .*Foo4.* appears to be a "
+            r"non-schema 'sqlalchemy.sql.column\(\)' object; ",
+        ):
+            class MyMixin2(object):
+                @declared_attr
+                def x(cls):
+                    return sa.sql.expression.column(Integer)
+
+                y = Column(Integer)
+
+            class Foo4(MyMixin2, Base):
+                __tablename__ = 'foo4'
+
+                id = Column(Integer, primary_key=True)
+
     def test_column_named_twice(self):
         def go():
             class Foo(Base):