Fixed #23913 -- Deprecated the = comparison in if template tag.

tests/template_tests/syntax_tests/test_if.py

@@ -1,5 +1,8 @@
+import warnings
+
 from django.template import TemplateSyntaxError
-from django.test import SimpleTestCase
+from django.test import ignore_warnings, SimpleTestCase
+from django.utils.deprecation import RemovedInDjango20Warning
 
 from ..utils import setup, TestObj
 
@@ -521,3 +524,42 @@ class IfTagTests(SimpleTestCase):
     def test_if_tag_badarg04(self):
         output = self.engine.render_to_string('if-tag-badarg04')
         self.assertEqual(output, 'no')
+
+    @setup({'if-tag-eq-deprecated': '{% if foo = bar %}yes{% else %}no{% endif %}'},
+        test_once=True)
+    def test_if_tag_eq_deprecated(self):
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.simplefilter('always')
+            output = self.engine.render_to_string('if-tag-eq-deprecated')
+            self.assertEqual(output, 'yes')
+        self.assertEqual(len(warns), 1)
+        self.assertEqual(
+            str(warns[0].message),
+            "Operator '=' is deprecated and will be removed in Django 2.0. "
+            "Use '==' instead."
+        )
+
+
+@ignore_warnings(category=RemovedInDjango20Warning)
+class TestEqualitySingleEqualsSign(SimpleTestCase):
+    # The following tests should be changed to template.TemplateSyntaxError
+    # (or simply removed) when the deprecation path ends in Django 2.0.
+    @setup({'if-tag-eq01': '{% if foo = bar %}yes{% else %}no{% endif %}'})
+    def test_if_tag_eq01(self):
+        output = self.engine.render_to_string('if-tag-eq01', {'foo': 1})
+        self.assertEqual(output, 'no')
+
+    @setup({'if-tag-eq02': '{% if foo = bar %}yes{% else %}no{% endif %}'})
+    def test_if_tag_eq02(self):
+        output = self.engine.render_to_string('if-tag-eq02', {'foo': 1, 'bar': 1})
+        self.assertEqual(output, 'yes')
+
+    @setup({'if-tag-eq03': '{% if foo = bar %}yes{% else %}no{% endif %}'})
+    def test_if_tag_eq03(self):
+        output = self.engine.render_to_string('if-tag-eq03', {'foo': 1, 'bar': 2})
+        self.assertEqual(output, 'no')
+
+    @setup({'if-tag-eq04': '{% if foo == \'\' %}yes{% else %}no{% endif %}'})
+    def test_if_tag_eq04(self):
+        output = self.engine.render_to_string('if-tag-eq04')
+        self.assertEqual(output, 'no')