- add logic to compiler such that if stack is empty, we just

stringify a _label_reference() as is.
- add .key to _label_reference(), so that when _make_proxy()
is called, we don't call str() on it anyway.
- add a test to exercise Query's behavior of adding all the order_by
expressions to the columns list of the select, assert that things
work out when we have a _label_reference there, that it gets sucked
into the columns list and spit out on the other side, it's referred
to appropriately, etc.   _label_reference() could theoretically
be resolved at the point we iterate _raw_columns() but
it's better to just let things work as they already do (except
nicer, since we get "tablename.colname" instead of just "somename"
 in the columns list) so that we aren't adding a ton of overhead
to _columns_plus_names in the common case.

3 files changed, 13 insertions, 2 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index e4597dcd8..23e5456a7 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -495,6 +495,12 @@ class SQLCompiler(Compiled):
         return "(" + grouping.element._compiler_dispatch(self, **kwargs) + ")"
 
     def visit_label_reference(self, element, **kwargs):
+        if not self.stack:
+            # compiling the element outside of the context of a SELECT
+            return self.process(
+                element._text_clause
+            )
+
         selectable = self.stack[-1]['selectable']
         try:
             col = selectable._inner_column_dict[element.text]
@@ -504,7 +510,7 @@ class SQLCompiler(Compiled):
                 "Can't resolve label reference %r; converting to text()",
                 util.ellipses_string(element.text))
             return self.process(
-                elements.TextClause._create_text(element.text)
+                element._text_clause
             )
         else:
             kwargs['render_label_as_label'] = col
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index 0ea05fa0e..984cfe0ee 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -2292,7 +2292,11 @@ class _label_reference(ColumnElement):
     __visit_name__ = 'label_reference'
 
     def __init__(self, text):
-        self.text = text
+        self.text = self.key = text
+
+    @util.memoized_property
+    def _text_clause(self):
+        return TextClause._create_text(self.text)
 
 
 class UnaryExpression(ColumnElement):
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index cf2c213d2..a49493995 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -2976,6 +2976,7 @@ class Select(HasPrefixes, GenerativeSelect):
             def name_for_col(c):
                 if c._columns_clause_label is None:
                     return (None, c)
+
                 name = c._columns_clause_label
                 if name in names:
                     name = c.anon_label