Fixed #28353 -- Fixed some GIS functions when queryset is evaluated more than once.

Reverted test for refs #27603 in favor of using FuncTestMixin.

tests/gis_tests/utils.py

@@ -1,8 +1,11 @@
+import copy
 import unittest
 from functools import wraps
+from unittest import mock
 
 from django.conf import settings
 from django.db import DEFAULT_DB_ALIAS, connection
+from django.db.models.expressions import Func
 
 
 def skipUnlessGISLookup(*gis_lookups):
@@ -56,3 +59,39 @@ elif spatialite:
     from django.contrib.gis.db.backends.spatialite.models import SpatialiteSpatialRefSys as SpatialRefSys
 else:
     SpatialRefSys = None
+
+
+class FuncTestMixin:
+    """Assert that Func expressions aren't mutated during their as_sql()."""
+    def setUp(self):
+        def as_sql_wrapper(original_as_sql):
+            def inner(*args, **kwargs):
+                func = original_as_sql.__self__
+                # Resolve output_field before as_sql() so touching it in
+                # as_sql() won't change __dict__.
+                func.output_field
+                __dict__original = copy.deepcopy(func.__dict__)
+                result = original_as_sql(*args, **kwargs)
+                msg = '%s Func was mutated during compilation.' % func.__class__.__name__
+                self.assertEqual(func.__dict__, __dict__original, msg)
+                return result
+            return inner
+
+        def __getattribute__(self, name):
+            if name != vendor_impl:
+                return __getattribute__original(self, name)
+            try:
+                as_sql = __getattribute__original(self, vendor_impl)
+            except AttributeError:
+                as_sql = __getattribute__original(self, 'as_sql')
+            return as_sql_wrapper(as_sql)
+
+        vendor_impl = 'as_' + connection.vendor
+        __getattribute__original = Func.__getattribute__
+        self.func_patcher = mock.patch.object(Func, '__getattribute__', __getattribute__)
+        self.func_patcher.start()
+        super().setUp()
+
+    def tearDown(self):
+        super().tearDown()
+        self.func_patcher.stop()