Allow stringify compiler to render unnamed column

Stringify of expression with unnamed :class:`.Column` objects, as
occurs in lots of situations including ORM error reporting,
will now render the name in string context as "<name unknown>"
rather than raising a compile error.

Change-Id: I76f637c5eb4cfdb1b526964cb001565b97e296da
Fixes: #3789

1 files changed, 11 insertions, 2 deletions

diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index a0db9864e..6896c9857 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -2432,14 +2432,16 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
         assert_raises_message(
             exc.CompileError,
             "Cannot compile Column object until its 'name' is assigned.",
-            str, sel2
+            sel2.compile,
+            dialect=default.DefaultDialect()
         )
 
         sel3 = select([my_str]).as_scalar()
         assert_raises_message(
             exc.CompileError,
             "Cannot compile Column object until its 'name' is assigned.",
-            str, sel3
+            sel3.compile,
+            dialect=default.DefaultDialect()
         )
 
         my_str.name = 'foo'
@@ -2709,6 +2711,13 @@ class StringifySpecialTest(fixtures.TestBase):
             "FROM mytable WHERE mytable.myid = :myid_1"
         )
 
+    def test_unnamed_column(self):
+        stmt = Column(Integer) == 5
+        eq_ignore_whitespace(
+            str(stmt),
+            '"<name unknown>" = :param_1'
+        )
+
     def test_cte(self):
         # stringify of these was supported anyway by defaultdialect.
         stmt = select([table1.c.myid]).cte()