ERP5.Document.SupplyLine: Recycle existing Predicates.

Rather than deleting them to just immediately create new ones with the
same ids but different uids.
Also, modernise code and follow naming conventions and coding style.

product/ERP5/Document/SupplyLine.py

@@ -197,41 +197,48 @@ class SupplyLine(Path, Amount, XMLMatrix):
         Update the quantity predicate for this price parameter
       """
       quantity_step_list = self.getQuantityStepList(price_parameter=price_parameter)
-      quantity_step_list.sort()
-
-      # remove old predicates
-      for pid in self.getQuantityPredicateIdList(price_parameter):
-        self.deleteContent(pid)
-
+      unused_predicate_id_set = self.getQuantityPredicateIdList(price_parameter)
       if quantity_step_list:
+        quantity_step_list.sort()
         quantity_step_list = [None] + quantity_step_list + [None]
-        # With this script, we can change the title of the predicate
-        script = getattr(self, 'SupplyLine_getTitle', None)
+        getTitle = getattr(
+          self,
+          'SupplyLine_getTitle',
+          lambda min, max: (
+            (
+              '' if min is None else '%s <= ' % (min, )
+            ) + 'quantity' + (
+              '' if max is None else ' < %s' % (max, )
+            )
+          ),
+        )
         predicate_id_start_with = "quantity_range"
         if price_parameter not in ("base_price", "slice_base_price"):
-          predicate_id_start_with = "%s_%s" % \
-              (price_parameter, predicate_id_start_with)
-        for i in range(0, len(quantity_step_list)-1):
+          predicate_id_start_with = "%s_%s" % (
+            price_parameter,
+            predicate_id_start_with,
+          )
+        for i in range(len(quantity_step_list) - 1):
           min_quantity = quantity_step_list[i]
-          max_quantity = quantity_step_list[i+1]
-          # XXX Hardcoded portal type name
-          p = self.newContent(id='%s_%s' % (predicate_id_start_with, str(i)),
-                              portal_type='Predicate', int_index=i+1)
-          p.setCriterionPropertyList(('quantity', ))
-          p.setCriterion(
+          max_quantity = quantity_step_list[i + 1]
+          predicate_id = '%s_%s' % (predicate_id_start_with, i)
+          try:
+            predicate_value = self[predicate_id]
+          except KeyError:
+            # XXX Hardcoded portal type name
+            predicate_value = self.newContent(
+              id='%s_%s' % (predicate_id_start_with, i),
+              portal_type='Predicate',
+              int_index=i + 1,
+            )
+          else:
+            unused_predicate_id_set.remove(predicate_id)
+          predicate_value.setTitle(getTitle(min=min_quantity, max=max_quantity))
+          predicate_value.setCriterionPropertyList(('quantity', ))
+          predicate_value.setCriterion(
             'quantity',
             min=min_quantity,
-            max=(None if price_parameter == 'slice_base_price' else max_quantity)
+            max=(None if price_parameter == 'slice_base_price' else max_quantity),
           )
-          if script is not None:
-            title = script(min=min_quantity, max=max_quantity)
-            p.setTitle(title)
-          else:
-            if min_quantity is None:
-              p.setTitle('quantity < %s' % max_quantity)
-            elif max_quantity is None:
-              p.setTitle('%s <= quantity' % min_quantity)
-            else:
-              p.setTitle('%s <= quantity < %s' % (min_quantity, max_quantity))
-
-
+      if unused_predicate_id_set:
+        self.deleteContent(unused_predicate_id_set)