general: update formdata in context for lazy evaluation (#47715)

wcs/fields.py

@@ -1972,6 +1972,10 @@ class PageCondition(Condition):
                 self.id_dict_var = id_dict_var
 
             def get_substitution_variables(self):
+                return {}
+
+            def get_static_substitution_variables(self):
+                # only for backward compatibility with python evaluations
                 return form_live_data
 
             def __eq__(self, other):
@@ -1986,6 +1990,13 @@ class PageCondition(Condition):
             # ie do nothing on first page condition
             get_publisher().substitutions.feed(ConditionVars(id(dict_vars)))
 
+            # alter top-of-stack formdata with data from submitted form
+            from wcs.formdata import FormData
+            for source in reversed(get_publisher().substitutions.sources):
+                if isinstance(source, FormData):
+                    source.data.update(dict_vars)
+                    break
+
         data = super(PageCondition, self).get_data()
         # 2) add live data as var_ variables for local evaluation only, for
         # backward compatibility. They are not added globally as they would