feed current formdata for substitution variables, even if incomplete

wcs/forms/root.ptl

@@ -365,10 +365,15 @@ class FormPage(Directory):
                     _('You need to enable javascript to complete this form')
             '</noscript>'
         displayed_fields = []
-        form = self.formdef.create_form(page_no, displayed_fields)
 
         session = get_session()
 
+        if page_no > 0:
+            magictoken = get_request().form['magictoken']
+            self.feed_current_data(magictoken)
+
+        form = self.formdef.create_form(page_no, displayed_fields)
+
         if True or [x for x in displayed_fields if x.prefill and
                 x.prefill.get('type') == 'wsf'] and (
                     session.lasso_session_dump and
@@ -436,14 +441,6 @@ class FormPage(Directory):
                                     v = user.form_data.get(x)
                                     break
                     elif t == 'formula':
-                        # create a fake FormData to feed variables
-                        formdata = FormData()
-                        formdata._formdef = self.formdef
-                        formdata.user = get_request().user
-                        formdata.data = data
-                        formdata.status = str('')
-                        get_publisher().substitutions.feed(formdata)
-                        formula = field.prefill.get('value')
                         variables = get_publisher().substitutions.get_context_variables()
                         try:
                             v = str(eval(formula, variables))
@@ -482,6 +479,15 @@ class FormPage(Directory):
 
         form.render()
 
+    def feed_current_data(self, magictoken):
+        # create a fake FormData to feed variables
+        formdata = FormData()
+        formdata._formdef = self.formdef
+        formdata.user = get_request().user
+        formdata.data = get_session().get_by_magictoken(magictoken, {})
+        formdata.status = str('')
+        get_publisher().substitutions.feed(formdata)
+
     def _q_index(self, log_detail = None, editing = None):
         self.check_role()
         if self.formdef.is_disabled():
@@ -571,6 +577,9 @@ class FormPage(Directory):
                 magictoken = form.get_widget('magictoken').parse()
             except KeyError:
                 magictoken = randbytes(8)
+
+            self.feed_current_data(magictoken)
+
             form = self.formdef.create_form(page_no)
             form.add_submit('previous')
             if self.formdef.allow_drafts:
@@ -662,6 +671,7 @@ class FormPage(Directory):
         if step == 2:
             form.add_submit('previous')
             magictoken = form.get_widget('magictoken').parse()
+            self.feed_current_data(magictoken)
             form_data = session.get_by_magictoken(magictoken, {})
             signature = None