Fixed bug where the expression system relied upon the ``str()``

form of a some expressions when referring to the ``.c`` collection
on a ``select()`` construct, but the ``str()`` form isn't available
since the element relies on dialect-specific compilation constructs,
notably the ``__getitem__()`` operator as used with a Postgresql
``ARRAY`` element.  The fix also adds a new exception class
:class:`.UnsupportedCompilationError` which is raised in those cases
where a compiler is asked to compile something it doesn't know
how to.  Also in 0.8.3.
[ticket:2780]

1 files changed, 13 insertions, 0 deletions

diff --git a/test/sql/test_selectable.py b/test/sql/test_selectable.py
index 335083ce1..df174fb25 100644
--- a/test/sql/test_selectable.py
+++ b/test/sql/test_selectable.py
@@ -148,6 +148,19 @@ class SelectableTest(fixtures.TestBase, AssertsExecutionResults, AssertsCompiled
         s = select([t])._clone()
         assert c in s.c.bar.proxy_set
 
+
+    def test_no_error_on_unsupported_expr_key(self):
+        from sqlalchemy.dialects.postgresql import ARRAY
+
+        t = table('t', column('x', ARRAY(Integer)))
+
+        expr = t.c.x[5]
+        s = select([t, expr])
+        eq_(
+            s.c.keys(),
+            ['x', expr.anon_label]
+        )
+
     def test_cloned_intersection(self):
         t1 = table('t1', column('x'))
         t2 = table('t2', column('x'))