Ticket #5908: 5908-resetcycle.4.diff

django/template/defaulttags.py

@@ -65 +65 @@
         self.variable_name = variable_name
         self.silent = silent
         self.escape = escape        # only while the "future" version exists
+        
+    def reset(self, context):
+        context.render_context[self] = itertools_cycle(self.cyclevars)
 
     def render(self, context):
         if self not in context.render_context:
@@ -80 +83 @@
             value = mark_safe(value)
         return render_value_in_context(value, context)
 
+class ResetCycleNode(Node):
+    def __init__(self, node):
+        self.node = node
+    def render(self, context):
+        self.node.reset(context)
+        return ''
+
 class DebugNode(Node):
     def render(self, context):
         from pprint import pformat
@@ -578 +588 @@
     # Ugly hack warning: This stuffs the named template dict into parser so
     # that names are only unique within each template (as opposed to using
     # a global variable, which would make cycle names have to be unique across
-    # *all* templates.
+    # *all* templates. Also keeps last unnamed node in the parser.
 
     args = token.split_contents()
 
@@ -623 +633 @@
     else:
         values = [parser.compile_filter(arg) for arg in args[1:]]
         node = CycleNode(values, escape=escape)
+        parser._lastUnnamedCycleNode = node
     return node
+    
+@register.tag
+def resetcycle(parser, token):
+    """
+    Resets a cycle tag.
+
+    If an argument is given, resets the last rendered cycle tag whose name
+    matches the argument, else resets last rendered unnamed cycle tag.
+
+    """
+    args = token.split_contents()
+
+    if len(args) > 2:
+        raise TemplateSyntaxError("%r tag accepts at most one argument."
+                                  % args[0])
+    if len(args) == 2:
+        name = args[1]
+        try:
+            return ResetCycleNode(parser._namedCycleNodes[name])
+        except AttributeError:
+            raise TemplateSyntaxError("No named cycles in template. "
+                                      "%r is not defined" % name)
+        except KeyError:
+            raise TemplateSyntaxError("Named cycle %r does not exist" % name)
+    try:
+        return ResetCycleNode(parser._lastUnnamedCycleNode)
+    except AttributeError:
+        raise TemplateSyntaxError("No unnamed cycles in template.")
 
 @register.tag
 def csrf_token(parser, token):

docs/ref/templates/builtins.txt

@@ -149 +149 @@
 
 Note that currently the variables included in the cycle will not be escaped.
 Any HTML or Javascript code contained in the printed variable will be rendered
-as-is, which could potentially lead to security issues.
+as-is, which could potentially lead to security issues.86
+
+You can use the `resetcycle`_ tag to reset a ``{% cycle %}`` tag to restart
+from its first value when it's next encountered.
 
 For backwards compatibility, the ``{% cycle %}`` tag supports the much inferior
 old syntax from previous Django versions. You shouldn't use this in any new
@@ -893 +896 @@
 ``{{ country.grouper }}`` will now display the value fields from the
 ``choices`` set rather than the keys.
 
+.. templatetag:: resetcycle
+
+resetcycle
+^^^^^^^^^^
+
+Resets a previous `cycle`_ so that it restarts from its first item at its next
+invocation.  Without arguments, ``{% resetcycle %}`` will reset the last
+unnamed ``{% cycle %}`` defined in the template.
+
+Example usage::
+
+    {% for coach in coach_list %}
+        <h1>{{ coach.name }}</h1>
+        {% for athlete in coach.athlete_set.all %}
+            <p class="{% cycle 'odd' 'even' %}">{{ athlete.name }}</p>
+        {% endfor %}
+        {% resetcycle %}
+    {% endfor %}
+
+The athlete list for every coach starts with ``class="odd"``.  Without the
+``{% resetcycle %}`` tag, the first athlete of a coach might be rendered with
+``class="even"`` if the last athlete of the previous coach had ``class="odd"``.
+
+You can also reset named cycle tags::
+
+    {% for item in list %}
+        <p class="{% cycle 'odd' 'evn' as stripe %} {% cycle 'majr' 'minr' 'minr' 'minr' 'minr' as tick %}">
+            {{ item.data }}
+        </p>
+        {% ifchanged item.category %}
+            <h1>{{ item.category }}</h1>
+            {% if not forloop.first %}{% resetcycle tick %}{% endif %}
+        {% endifchanged %}
+    {% endfor %}
+
+In this example we have both the alternating odd/even rows and a "major" row
+every fifth row.  Only the five-row cycle is reset when a category changes.
+
 .. templatetag:: spaceless
 
 spaceless

tests/template_tests/tests.py

@@ -818 +818 @@
             'cycle26': ('{% load cycle from future %}{% cycle a b as ab %}{% cycle ab %}', {'a': '<', 'b': '>'}, '&lt;&gt;'),
             'cycle27': ('{% load cycle from future %}{% autoescape off %}{% cycle a b as ab %}{% cycle ab %}{% endautoescape %}', {'a': '<', 'b': '>'}, '<>'),
             'cycle28': ('{% load cycle from future %}{% cycle a|safe b as ab %}{% cycle ab %}', {'a': '<', 'b': '>'}, '<&gt;'),
+            
+            ### RESETCYCLE TAG ########################################################
+            'resetcycle01': ("{% resetcycle %}", {}, template.TemplateSyntaxError),
+            'resetcycle02': ("{% resetcycle undefinedcycle %}", {}, template.TemplateSyntaxError),
+            'resetcycle03': ("{% cycle 'a' 'b' 'c' as abc %}{% resetcycle %}", {}, template.TemplateSyntaxError),
+            'resetcycle04': ("{% cycle 'a' 'b' 'c' %}{% resetcycle undefinedcycle %}", {}, template.TemplateSyntaxError),
+            'resetcycle05': ("{% cycle 'a' 'b' 'c' as abc %}{% resetcycle undefinedcycle %}", {}, template.TemplateSyntaxError),
+            'resetcycle06': ("{% for i in test %}{% cycle 'a' 'b' %}{% resetcycle %}{% endfor %}", {'test': range(5)}, 'aaaaa'),
+            'resetcycle07': ("{% cycle 'a' 'b' 'c' as abc %}{% for i in test %}{% cycle abc %}{% cycle '-' '+' %}{% resetcycle %}{% endfor %}", {'test': range(5)}, 'ab-c-a-b-c-'),
+            'resetcycle08': ("{% cycle 'a' 'b' 'c' as abc %}{% for i in test %}{% resetcycle abc %}{% cycle abc %}{% cycle '-' '+' %}{% endfor %}", {'test': range(5)}, 'aa-a+a-a+a-'),
+            'resetcycle09': ("{% for i in outer %}{% for j in inner %}{% cycle 'a' 'b' %}{% endfor %}{% resetcycle %}{% endfor %}", {'outer': range(2), 'inner': range(3)}, 'abaaba'),
+            'resetcycle10': ("{% for i in outer %}{% cycle 'a' 'b' %}{% for j in inner %}{% cycle 'X' 'Y' %}{% endfor %}{% resetcycle %}{% endfor %}", {'outer': range(2), 'inner': range(3)}, 'aXYXbXYX'),
+            'resetcycle11': ("{% for i in test %}{% cycle 'X' 'Y' 'Z' as XYZ %}{% cycle 'a' 'b' 'c' as abc %}{% ifequal i 1 %}{% resetcycle abc %}{% endifequal %}{% endfor %}", {'test': range(5)}, 'XaYbZaXbYc'),
+            'resetcycle12': ("{% for i in test %}{% cycle 'X' 'Y' 'Z' as XYZ %}{% cycle 'a' 'b' 'c' as abc %}{% ifequal i 1 %}{% resetcycle XYZ %}{% endifequal %}{% endfor %}", {'test': range(5)}, 'XaYbXcYaZb'),
 
             ### EXCEPTIONS ############################################################