Amount Generator: fix sorting by dependency resolution

The attempt to make sorting stable in commit
28698f35
was broken because there may be pairs of items that can't be compared,
and list.sort() relies on < transitivity.

product/ERP5/mixin/amount_generator.py

@@ -185,9 +185,6 @@ class BaseAmountResolver(BaseAmountDict):
             self |= node()
       return self
 
-    def __lt__(self, other):
-      return not other().isdisjoint(self.property_dict['_contribution'])
-
   def __init__(self, cache, method_kw):
     self._dict = cache.setdefault(None, {})
     self._cache = cache
@@ -207,9 +204,20 @@ class BaseAmountResolver(BaseAmountDict):
           recurseApplicationDependencies(*variated_base_amount)
         for variated_base_amount in property_dict['_contribution']:
           contribution_dict[variated_base_amount].append(node)
-      del self._resolving
-      node_list.sort()
-      property_dict_list[:] = (node.property_dict for node in node_list)
+      del self._resolving, property_dict_list[:]
+      # O(n^2) sorting !! Yeah, shame on me but is it possible to do better
+      # when there are pairs of items that can't be compared (e.g. A & C in
+      # A -> B <- C), and original order shoud be preserved if possible ?
+      # Anyway, there are usually very few objects.
+      for node in reversed(node_list):
+        isdisjoint = node().isdisjoint
+        for i, property_dict in enumerate(property_dict_list):
+          if not isdisjoint(property_dict['_contribution']):
+            property_dict_list.insert(i, node.property_dict)
+            break
+        else:
+          property_dict_list.append(node.property_dict)
+      property_dict_list.reverse()
 
   def getBaseAmountList(self):
     return ()