[1.8.x] Moved ifchanged tests into syntax_tests/test_if_changed.py.

Backport of 3d8fee605184d8ffa47a32546298b52b52d7a087 from master

1 files changed, 35 insertions, 0 deletions

diff --git a/tests/template_tests/syntax_tests/test_if_changed.py b/tests/template_tests/syntax_tests/test_if_changed.py
index 0d94365733..33e66880dd 100644
--- a/tests/template_tests/syntax_tests/test_if_changed.py
+++ b/tests/template_tests/syntax_tests/test_if_changed.py
@@ -1,3 +1,4 @@
+from django.template import Context, Template
 from django.test import SimpleTestCase
 
 from ..utils import setup
@@ -152,3 +153,37 @@ class IfChangedTagTests(SimpleTestCase):
         """
         output = self.engine.render_to_string('ifchanged-filter-ws', {'num': (1, 2, 3)})
         self.assertEqual(output, '..1..2..3')
+
+
+class IfChangedTests(SimpleTestCase):
+
+    def test_ifchanged_concurrency(self):
+        """
+        #15849 -- ifchanged should be thread-safe.
+        """
+        template = Template('[0{% for x in foo %},{% with var=get_value %}{% ifchanged %}{{ var }}{% endifchanged %}{% endwith %}{% endfor %}]')
+
+        # Using generator to mimic concurrency.
+        # The generator is not passed to the 'for' loop, because it does a list(values)
+        # instead, call gen.next() in the template to control the generator.
+        def gen():
+            yield 1
+            yield 2
+            # Simulate that another thread is now rendering.
+            # When the IfChangeNode stores state at 'self' it stays at '3' and skip the last yielded value below.
+            iter2 = iter([1, 2, 3])
+            output2 = template.render(Context({'foo': range(3), 'get_value': lambda: next(iter2)}))
+            self.assertEqual(output2, '[0,1,2,3]', 'Expected [0,1,2,3] in second parallel template, got {}'.format(output2))
+            yield 3
+
+        gen1 = gen()
+        output1 = template.render(Context({'foo': range(3), 'get_value': lambda: next(gen1)}))
+        self.assertEqual(output1, '[0,1,2,3]', 'Expected [0,1,2,3] in first template, got {}'.format(output1))
+
+    def test_ifchanged_render_once(self):
+        """
+        #19890. The content of ifchanged template tag was rendered twice.
+        """
+        template = Template('{% ifchanged %}{% cycle "1st time" "2nd time" %}{% endifchanged %}')
+        output = template.render(Context({}))
+        self.assertEqual(output, '1st time')