omit text from selected_columns; clear memoizations

Fixed regression where usage of the :func:`_sql.text` construct inside the
columns clause of a :class:`_sql.Select` construct, which is better handled
by using a :func:`_sql.literal_column` construct, would nonetheless prevent
constructs like :func:`_sql.union` from working correctly. Other use cases,
such as constructing subuqeries, continue to work the same as in prior
versions where the :func:`_sql.text` construct is silently omitted from the
collection of exported columns. Also repairs similar use within the
ORM.

This adds a new internal method _all_selected_columns.  The existing
"selected_columns" collection can't store a TextClause and this never
worked, so they are omitted.  The TextClause is also not "exported",
i.e. available for SELECT from a subquery, as was already the case
in 1.3, so the "exported_columns" and "exported_columns_iterator"
accessors are where we now omit TextClause.

Fixed regression involving legacy methods such as
:meth:`_sql.Select.append_column` where internal assertions would fail.

Fixes: #6343
Fixes: #6261
Change-Id: I7c2e5b9ae5d94131c77599a020f4310dcf812bcf

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/context.py b/lib/sqlalchemy/orm/context.py
index b0b8faee7..6cdad9f41 100644
--- a/lib/sqlalchemy/orm/context.py
+++ b/lib/sqlalchemy/orm/context.py
@@ -789,6 +789,14 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
 
     @classmethod
     def exported_columns_iterator(cls, statement):
+        return (
+            elem
+            for elem in cls.all_selected_columns(statement)
+            if not elem._is_text_clause
+        )
+
+    @classmethod
+    def all_selected_columns(cls, statement):
         for element in statement._raw_columns:
             if (
                 element.is_selectable
@@ -2614,7 +2622,10 @@ class _RawColumnEntity(_ColumnEntity):
         self.expr = column
         self.raw_column_index = raw_column_index
         self.translate_raw_column = raw_column_index is not None
-        self._label_name = compile_state._label_convention(column)
+        if column._is_text_clause:
+            self._label_name = None
+        else:
+            self._label_name = compile_state._label_convention(column)
 
         if parent_bundle:
             parent_bundle._entities.append(self)