Commit 636c45fc authored by Christopher Medrela's avatar Christopher Medrela
Browse files

Fixed #19890 -- ifchanged templatetag rendered its content twice 

The content of ifchanged template tag was rendered twice: first time, to
compare it with the previous value and the second time, to return the
rendered output.
parent 8503120c

django/template/defaulttags.py

+3 −2
Original line number Diff line number Diff line
@@ -223,6 +223,7 @@ class IfChangedNode(Node): 
        if self not in state_frame:

            state_frame[self] = None



        nodelist_true_output = None

        try:

            if self._varlist:

                # Consider multiple parameters.  This automatically behaves
@@ -230,13 +231,13 @@ class IfChangedNode(Node): 
                compare_to = [var.resolve(context, True) for var in self._varlist]

            else:

                # The "{% ifchanged %}" syntax (without any variables) compares the rendered output.

                compare_to = self.nodelist_true.render(context)

                compare_to = nodelist_true_output = self.nodelist_true.render(context)

        except VariableDoesNotExist:

            compare_to = None



        if compare_to != state_frame[self]:

            state_frame[self] = compare_to

            return self.nodelist_true.render(context)

            return nodelist_true_output or self.nodelist_true.render(context)  # render true block if not already rendered

        elif self.nodelist_false:

            return self.nodelist_false.render(context)

        return ''

tests/regressiontests/templates/tests.py

+12 −0
Original line number Diff line number Diff line
@@ -441,6 +441,18 @@ class Templates(TestCase): 
        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 {0}'.format(output1))



    def test_ifchanged_render_once(self):

        """ Test for ticket #19890. The content of ifchanged template tag was

        rendered twice."""



        template = Template('{% ifchanged %}{{ gen.next }}{% endifchanged %}')

        def gen():

            for i in xrange(1,10):

                yield 'iteration no %d' % i



        output = template.render(Context({'gen': gen()}))

        self.assertEqual(output, 'iteration no 1')



    def test_templates(self):

        template_tests = self.get_template_tests()

        filter_tests = filters.get_filter_tests()