Ticket #12884: form_wizard.diff

django/contrib/formtools/wizard.py

@@ -76 +76 @@
             form = self.get_form(current_step, request.POST)
         else:
             form = self.get_form(current_step)
-        if form.is_valid():
+        if self.advance_form(request, form, current_step) and form.is_valid():
             self.process_step(request, form, current_step)
             next_step = current_step + 1
 
@@ -217 +217 @@
             previous_fields=previous_fields
         ), context_instance=RequestContext(request))
 
+    def advance_form(self, request, form, step):
+        """
+        Hook to decide if the next form in the list should be displayed.
+
+        There are occassions when you may want to have a form with a button
+        that goes backwards. You can make the boolean decision to advance
+        to the next form, typically, using the existing form and the
+        current request.
+
+        The rationale is that you may want to include the existing form data
+        when the form is being redisplayed.
+        """
+        return True
+
     def process_step(self, request, form, step):
         """
         Hook for modifying the FormWizard's internal state, given a fully