Template tags calls form permission

This commit will make the templatetags to pull the form rendering
permission from the form object.

Also there will be two attributes set in the form when redering
purchase_permitted, and reason. This will allow a better information to
be displayed on the template.

oscar/apps/basket/forms.py

             else:
                 self._create_product_fields(instance)
 
-    def is_allowed_to_purchase(self, product, desired_qty):
-        return product.is_purchase_permitted(user=self.request.user,
-                                                quantity=desired_qty)
+
+    def is_purchase_permitted(self, user, product, desired_qty):
+        return product.is_purchase_permitted(user=user, quantity=desired_qty)
 
     def cleaned_options(self):
         """
                                                 self.cleaned_options())
         desired_qty = current_qty + self.cleaned_data.get('quantity', 1)
 
-        is_available, reason = self.is_allowed_to_purchase(product, desired_qty)
+        is_permitted, reason = self.is_purchase_permitted(self.request.user,
+                                                    product, desired_qty)
 
-        if not is_available:
+        if not is_permitted:
             raise forms.ValidationError(reason)
         return self.cleaned_data
 

oscar/templates/oscar/catalogue/partials/add_to_basket_form.html

 
 {% if product.is_available_to_buy %}
     {% basket_form request product as basket_form %}
+    {% if basket_form.purchase_permitted %}
     <form action="{% url basket:add %}" method="post" class="form-stacked">
         {% csrf_token %}
         {% include "partials/form_fields.html" with form=basket_form %}
 			<button type="submit" class="btn btn-large btn-primary btn-full" value="Add to basket">{% trans "Add to basket" %}</button>
         </div>
     </form>
+    {% else %}
+        {{ basket_form.reason }}
+    {% endif %}
 {% else %}
 	{% if has_active_alert %}
 	<p>{% trans "You have an active stock alert for this product." %}</p>

oscar/templates/oscar/catalogue/partials/add_to_basket_form_compact.html

 {% load i18n %}
 
 {% basket_form request product as basket_form single %}
+
+{% if basket_form.purchase_permitted %}
 <form action="{% url basket:add %}" method="post">
     {% csrf_token %}
     {{ basket_form.as_p }}
         <button type="submit" class="btn btn-primary btn-full">{% trans "Add to basket" %}</button>
     {% endif %}
 </form>
+{% else %}
+    {{ basket_form.reason }}
+{% endif %}

oscar/templatetags/basket_tags.py

             "{%% basket_form request product_var as "
             "form_var %%}" % tokens[0])
 
-    request, product_var, form_var = tokens[1], tokens[2], tokens[4]
+    request_var, product_var, form_var = tokens[1], tokens[2], tokens[4]
 
     quantity_type = tokens[5] if len(tokens) == 6 else QNT_MULTIPLE
     if quantity_type not in (QNT_SINGLE, QNT_MULTIPLE):
         raise template.TemplateSyntaxError(
             "%r tag only accepts the following quantity types: "
             "'single', 'multiple'" % tokens[0])
-    return BasketFormNode(request, product_var, form_var, quantity_type)
+    return BasketFormNode(request_var, product_var, form_var, quantity_type)
 
 
 class BasketFormNode(template.Node):
 
     def render(self, context):
         try:
-            request = self.request_var.resolve(context)
+            self.request = self.request_var.resolve(context)
             product = self.product_var.resolve(context)
         except template.VariableDoesNotExist:
             return ''
             initial = {}
             if not product.is_group:
                 initial['product_id'] = product.id
-            context[self.form_var] = self.form_class(
-                request, instance=product, initial=initial)
+            self.form = self.form_class(
+                self.request, instance=product, initial=initial)
+
+            user = self.request.user
+            is_permitted, reason = self.form.is_purchase_permitted(user,
+                                                                product, 1)
+
+            self.form.purchase_permitted = is_permitted
+            self.form.reason = reason
+
+            context[self.form_var] = self.form
         return ''