Adjust form_field.html to pivot on widget type

This requires a new templatetag that annotates the field with the widget
type.  The motivation is so that normal forms (not using
form-horizontal) can render checkboxes differently - wrapping the input
in the label element.  This is advocated by bootstrap amongst others:
http://twitter.github.com/bootstrap/base-css.html#forms

At the moment, checkboxes rendered in a form with class
'form-horizontal' don't look right - they need some adjusting in the
CSS.

oscar/templates/oscar/partials/form_field.html

@@ -1,19 +1,42 @@
+{% load form_tags %}
+
+{# Make the field widget type available to templates #}
+{% annotate_form_field field %}
+
 <div class="control-group {% for error in field.errors %}error{% endfor %}">
     {% if field.is_hidden %}
         {{ field }}
     {% else %}
-        <label for="{{ field.auto_id }}" class="control-label {% if field.field.required %}required{% endif %}">{{ field.label }}{% if field.field.required %} <span>*</span>{% endif %}</label>
-        <div class="controls">
-            {{ field }}
-            {% for error in field.errors %}
-                <span class="help-block">{{ error }}</span>
-            {% endfor %}
-            {% if field.help_text %}
-                <span class='help-block'>
-					{# We allow HTML within form help fields #}
-                    {{ field.help_text|safe }}
-                </span>
-            {% endif %}
-        </div>
+		{# Check if field is a checkbox as we mark these up differently #}
+		{% if field.widget_type == 'CheckboxInput' %}
+			<label for="{{ field.auto_id }}" class="control-label checkbox {% if field.field.required %}required{% endif %}">{{ field.label }}{% if field.field.required %} <span>*</span>{% endif %}
+				{{ field }}
+			</label>
+			<div class="controls">
+				{% for error in field.errors %}
+					<span class="help-block">{{ error }}</span>
+				{% endfor %}
+				{% if field.help_text %}
+					<span class='help-block'>
+						{# We allow HTML within form help fields #}
+						{{ field.help_text|safe }}
+					</span>
+				{% endif %}
+			</div>
+		{% else %}
+			<label for="{{ field.auto_id }}" class="control-label {% if field.field.required %}required{% endif %}">{{ field.label }}{% if field.field.required %} <span>*</span>{% endif %}</label>
+			<div class="controls">
+				{{ field }}
+				{% for error in field.errors %}
+					<span class="help-block">{{ error }}</span>
+				{% endfor %}
+				{% if field.help_text %}
+					<span class='help-block'>
+						{# We allow HTML within form help fields #}
+						{{ field.help_text|safe }}
+					</span>
+				{% endif %}
+			</div>
+		{% endif %}
     {% endif %}
 </div>

oscar/templatetags/form_tags.py

@@ -0,0 +1,28 @@
+from django import template
+
+register = template.Library()
+
+
+@register.tag
+def annotate_form_field(parser, token):
+    """
+    Set an attribute on a form field with the widget type
+
+    This means templates can use the widget type to render things differently
+    if they want to.  Django doesn't make this available by default.
+    """
+    args = token.split_contents()
+    if len(args) < 2:
+        raise template.TemplateSyntaxError(
+            "annotate_form_field tag requires a form field to be passed")
+    return FormFieldNode(args[1])
+
+
+class FormFieldNode(template.Node):
+    def __init__(self, field_str):
+        self.field = template.Variable(field_str)
+
+    def render(self, context):
+        field = self.field.resolve(context)
+        field.widget_type = field.field.widget.__class__.__name__
+        return ''