3 files changed, 62 insertions, 4 deletions

diff --git a/test/orm/test_query.py b/test/orm/test_query.py
index 2bc0af3c2..068a7c893 100644
--- a/test/orm/test_query.py
+++ b/test/orm/test_query.py
@@ -3990,6 +3990,45 @@ class DistinctTest(QueryTest, AssertsCompiledSQL):
             dialect="postgresql",
         )
 
+    def test_columns_augmented_sql_three_using_label_reference(self):
+        User, Address = self.classes.User, self.classes.Address
+
+        sess = create_session()
+
+        q = (
+            sess.query(User.id, User.name.label("foo"), Address.id)
+            .distinct("name")
+            .order_by(User.id, User.name, Address.email_address)
+        )
+
+        # no columns are added when DISTINCT ON is used
+        self.assert_compile(
+            q,
+            "SELECT DISTINCT ON (users.name) users.id AS users_id, "
+            "users.name AS foo, addresses.id AS addresses_id FROM users, "
+            "addresses ORDER BY users.id, users.name, addresses.email_address",
+            dialect="postgresql",
+        )
+
+    def test_columns_augmented_sql_illegal_label_reference(self):
+        User, Address = self.classes.User, self.classes.Address
+
+        sess = create_session()
+
+        q = sess.query(User.id, User.name.label("foo"), Address.id).distinct(
+            "not a label"
+        )
+
+        from sqlalchemy.dialects import postgresql
+
+        assert_raises_message(
+            sa_exc.CompileError,
+            "Can't resolve label reference for ORDER BY / "
+            "GROUP BY / DISTINCT etc.",
+            q.with_labels().statement.compile,
+            dialect=postgresql.dialect(),
+        )
+
     def test_columns_augmented_sql_four(self):
         User, Address = self.classes.User, self.classes.Address
 
diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index ca73f6c18..486b54682 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -2073,7 +2073,8 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
         # to check the special thing CompoundSelect does with labels
         assert_raises_message(
             exc.CompileError,
-            "Can't resolve label reference for ORDER BY / GROUP BY. Textual "
+            "Can't resolve label reference for ORDER BY / GROUP BY / "
+            "DISTINCT etc. Textual "
             "SQL expression 'noname'",
             union(
                 select([table1.c.myid, table1.c.name]),
diff --git a/test/sql/test_text.py b/test/sql/test_text.py
index 3f12d06a9..3386d0aae 100644
--- a/test/sql/test_text.py
+++ b/test/sql/test_text.py
@@ -678,14 +678,16 @@ class TextErrorsTest(fixtures.TestBase, AssertsCompiledSQL):
 class OrderByLabelResolutionTest(fixtures.TestBase, AssertsCompiledSQL):
     __dialect__ = "default"
 
-    def _test_exception(self, stmt, offending_clause):
+    def _test_exception(self, stmt, offending_clause, dialect=None):
         assert_raises_message(
             exc.CompileError,
-            r"Can't resolve label reference for ORDER BY / GROUP BY. "
+            r"Can't resolve label reference for ORDER BY / GROUP BY / "
+            "DISTINCT etc. "
             "Textual SQL "
             "expression %r should be explicitly "
             r"declared as text\(%r\)" % (offending_clause, offending_clause),
             stmt.compile,
+            dialect=dialect,
         )
 
     def test_order_by_label(self):
@@ -736,6 +738,21 @@ class OrderByLabelResolutionTest(fixtures.TestBase, AssertsCompiledSQL):
         stmt = select([table1.c.myid]).order_by("foobar")
         self._test_exception(stmt, "foobar")
 
+    def test_distinct_label(self):
+
+        stmt = select([table1.c.myid.label("foo")]).distinct("foo")
+        self.assert_compile(
+            stmt,
+            "SELECT DISTINCT ON (foo) mytable.myid AS foo FROM mytable",
+            dialect="postgresql",
+        )
+
+    def test_unresolvable_distinct_label(self):
+        from sqlalchemy.dialects import postgresql
+
+        stmt = select([table1.c.myid.label("foo")]).distinct("not a label")
+        self._test_exception(stmt, "not a label", dialect=postgresql.dialect())
+
     def test_group_by_label(self):
         stmt = select([table1.c.myid.label("foo")]).group_by("foo")
         self.assert_compile(
@@ -890,7 +907,8 @@ class OrderByLabelResolutionTest(fixtures.TestBase, AssertsCompiledSQL):
 
         assert_raises_message(
             exc.CompileError,
-            r"Can't resolve label reference for ORDER BY / GROUP BY. "
+            r"Can't resolve label reference for ORDER BY / GROUP BY / "
+            "DISTINCT etc. "
             "Textual SQL "
             "expression 't1name' should be explicitly "
             r"declared as text\('t1name'\)",