Fixed #32068 -- Added error messages on get() with filters following union(), intersection(), and difference().

django/db/models/query.py

@@ -416,6 +416,11 @@ class QuerySet:
         Perform the query and return a single object matching the given
         keyword arguments.
         """
+        if self.query.combinator and (args or kwargs):
+            raise NotSupportedError(
+                'Calling QuerySet.get(...) with filters after %s() is not '
+                'supported.' % self.query.combinator
+            )
         clone = self._chain() if self.query.combinator else self.filter(*args, **kwargs)
         if self.query.can_filter() and not self.query.distinct_fields:
             clone = clone.order_by()

tests/queries/test_qs_combinators.py

@@ -341,3 +341,16 @@ class QuerySetSetOperationTests(TestCase):
                         msg % (operation, combinator),
                     ):
                         getattr(getattr(qs, combinator)(qs), operation)()
+
+    def test_get_with_filters_unsupported_on_combined_qs(self):
+        qs = Number.objects.all()
+        msg = 'Calling QuerySet.get(...) with filters after %s() is not supported.'
+        combinators = ['union']
+        if connection.features.supports_select_difference:
+            combinators.append('difference')
+        if connection.features.supports_select_intersection:
+            combinators.append('intersection')
+        for combinator in combinators:
+            with self.subTest(combinator=combinator):
+                with self.assertRaisesMessage(NotSupportedError, msg % combinator):
+                    getattr(qs, combinator)(qs).get(num=2)