Fixed #15570 -- Corrected a flaw in the design of the silent flag on {% cycle %}. Thanks to Brian Neal for the report, and to Andrew and Jannis for the design consult.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15773 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/template/defaulttags.py

@@ -111,12 +111,12 @@ class CycleNode(Node):
         if self not in context.render_context:
             # First time the node is rendered in template
             context.render_context[self] = itertools_cycle(self.cyclevars)
-            if self.silent:
-                return ''
         cycle_iter = context.render_context[self]
         value = cycle_iter.next().resolve(context)
         if self.variable_name:
             context[self.variable_name] = value
+        if self.silent:
+            return ''
         return value
 
 class DebugNode(Node):

docs/ref/templates/builtins.txt

@@ -102,11 +102,31 @@ outside of a loop. To do this, just give the ``{% cycle %}`` tag a name, using
 
     {% cycle 'row1' 'row2' as rowcolors %}
 
-From then on, you can insert the current value of the cycle wherever you'd like
-in your template::
+From then on, you can insert the current value of the cycle wherever
+you'd like in your template by referencing the cycle name as a context
+variable. If you want to move the cycle onto the next value, you use
+the cycle tag again, using the name of the variable. So, the following
+template::
 
-    <tr class="{% cycle rowcolors %}">...</tr>
-    <tr class="{% cycle rowcolors %}">...</tr>
+    <tr>
+        <td class="{% cycle 'row1' 'row2' as rowcolors %}">...</td>
+        <td class="{{ rowcolors }}">...</td>
+    </tr>
+    <tr>
+        <td class="{% cycle rowcolors %}">...</td>
+        <td class="{{ rowcolors }}">...</td>
+    </tr>
+
+would output::
+
+    <tr>
+        <td class="row1">...</td>
+        <td class="row1">...</td>
+    </tr>
+    <tr>
+        <td class="row2">...</td>
+        <td class="row2">...</td>
+    </tr>
 
 You can use any number of values in a ``{% cycle %}`` tag, separated by spaces.
 Values enclosed in single (``'``) or double quotes (``"``) are treated as
@@ -144,16 +164,25 @@ use the value in a nested loop or an included template. If you want to
 just declare the cycle, but not output the first value, you can add a
 ``silent`` keyword as the last keyword in the tag. For example::
 
-    {% cycle 'row1' 'row2' as rowcolors silent %}
     {% for obj in some_list %}
-        <tr class="{% cycle rowcolors %}">{{ obj }}</tr>
+        {% cycle 'row1' 'row2' as rowcolors silent %}
+        <tr class="{{ rowcolors }}">{% include "subtemplate.html " %}</tr>
     {% endfor %}
 
 This will output a list of ``<tr>`` elements with ``class``
-alternating between ``row1`` and ``row2``. If the ``silent`` keyword
-were to be omitted, ``row1`` would be emitted as normal text, outside
-the list of ``<tr>`` elements, and the first ``<tr>`` would have a
-class of ``row2``.
+alternating between ``row1`` and ``row2``; the subtemplate will have
+access to ``rowcolors`` in it's context that matches the class of the
+``<tr>`` that encloses it. If the ``silent`` keyword were to be
+omitted, ``row1`` would be emitted as normal text, outside the
+``<tr>`` element.
+
+When the silent keyword is used on a cycle definition, the silence
+automatically applies to all subsequent uses of the cycle tag. In,
+the following template would output *nothing*, even though the second
+call to ``{% cycle %}`` doesn't specify silent::
+
+    {% cycle 'row1' 'row2' as rowcolors silent %}
+    {% cycle rowcolors %}
 
 .. templatetag:: debug
 

tests/regressiontests/templates/tests.py

@@ -735,11 +735,15 @@ class Templates(unittest.TestCase):
             'cycle14': ("{% cycle one two as foo %}{% cycle foo %}", {'one': '1','two': '2'}, '12'),
             'cycle15': ("{% for i in test %}{% cycle aye bee %}{{ i }},{% endfor %}", {'test': range(5), 'aye': 'a', 'bee': 'b'}, 'a0,b1,a2,b3,a4,'),
             'cycle16': ("{% cycle one|lower two as foo %}{% cycle foo %}", {'one': 'A','two': '2'}, 'a2'),
-            'cycle17': ("{% cycle 'a' 'b' 'c' as abc silent %}{% cycle abc %}{% cycle abc %}{% cycle abc %}{% cycle abc %}", {}, "abca"),
+            'cycle17': ("{% cycle 'a' 'b' 'c' as abc silent %}{% cycle abc %}{% cycle abc %}{% cycle abc %}{% cycle abc %}", {}, ""),
             'cycle18': ("{% cycle 'a' 'b' 'c' as foo invalid_flag %}", {}, template.TemplateSyntaxError),
             'cycle19': ("{% cycle 'a' 'b' as silent %}{% cycle silent %}", {}, "ab"),
             'cycle20': ("{% cycle one two as foo %} & {% cycle foo %}", {'one' : 'A & B', 'two' : 'C & D'}, "A & B & C & D"),
             'cycle21': ("{% filter force_escape %}{% cycle one two as foo %} & {% cycle foo %}{% endfilter %}", {'one' : 'A & B', 'two' : 'C & D'}, "A & B & C & D"),
+            'cycle22': ("{% for x in values %}{% cycle 'a' 'b' 'c' as abc silent %}{{ x }}{% endfor %}", {'values': [1,2,3,4]}, "1234"),
+            'cycle23': ("{% for x in values %}{% cycle 'a' 'b' 'c' as abc silent %}{{ abc }}{{ x }}{% endfor %}", {'values': [1,2,3,4]}, "a1b2c3a4"),
+            'included-cycle': ('{{ abc }}', {'abc': 'xxx'}, 'xxx'),
+            'cycle24': ("{% for x in values %}{% cycle 'a' 'b' 'c' as abc silent %}{% include 'included-cycle' %}{% endfor %}", {'values': [1,2,3,4]}, "abca"),
 
             ### EXCEPTIONS ############################################################