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/test_gis_tests_utils.py

@@ -0,0 +1,52 @@
+from django.db import connection, models
+from django.db.models.expressions import Func
+from django.test import SimpleTestCase
+
+from .utils import FuncTestMixin
+
+
+def test_mutation(raises=True):
+    def wrapper(mutation_func):
+        def test(test_case_instance, *args, **kwargs):
+            class TestFunc(Func):
+                output_field = models.IntegerField()
+
+                def __init__(self):
+                    self.attribute = 'initial'
+                    super().__init__('initial', ['initial'])
+
+                def as_sql(self, *args, **kwargs):
+                    mutation_func(self)
+                    return '', ()
+
+            if raises:
+                msg = 'TestFunc Func was mutated during compilation.'
+                with test_case_instance.assertRaisesMessage(AssertionError, msg):
+                    getattr(TestFunc(), 'as_' + connection.vendor)(None, None)
+            else:
+                getattr(TestFunc(), 'as_' + connection.vendor)(None, None)
+
+        return test
+    return wrapper
+
+
+class FuncTestMixinTests(FuncTestMixin, SimpleTestCase):
+    @test_mutation()
+    def test_mutated_attribute(func):
+        func.attribute = 'mutated'
+
+    @test_mutation()
+    def test_mutated_expressions(func):
+        func.source_expressions.clear()
+
+    @test_mutation()
+    def test_mutated_expression(func):
+        func.source_expressions[0].name = 'mutated'
+
+    @test_mutation()
+    def test_mutated_expression_deep(func):
+        func.source_expressions[1].value[0] = 'mutated'
+
+    @test_mutation(raises=False)
+    def test_not_mutated(func):
+        pass