Do not use invoices function field for invoice exception

This allows to reuse the design for invoices linked differently to the purchase.

issue6274
review26161002

invoice.py

@@ -1,5 +1,6 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+from itertools import chain
 from functools import wraps
 from sql import Table
 
@@ -86,10 +87,7 @@ class Invoice:
     @ModelView.button
     @Workflow.transition('draft')
     def draft(cls, invoices):
-        Purchase = Pool().get('purchase.purchase')
-        purchases = Purchase.search([
-                ('invoices', 'in', [i.id for i in invoices]),
-                ])
+        purchases = list(chain(*(i.purchases for i in invoices)))
         if purchases and any(i.state == 'cancel' for i in invoices):
             cls.raise_user_error('reset_invoice_purchase')
 

purchase.py

@@ -1580,19 +1580,13 @@ class HandleInvoiceException(Wizard):
 
     def transition_handle(self):
         Purchase = Pool().get('purchase.purchase')
-        to_recreate = self.ask.recreate_invoices
-        domain_invoices = self.ask.domain_invoices
 
         purchase = Purchase(Transaction().context['active_id'])
 
-        skip = set(purchase.invoices_ignored)
-        skip.update(purchase.invoices_recreated)
         invoices_ignored = []
         invoices_recreated = []
-        for invoice in purchase.invoices:
-            if invoice not in domain_invoices or invoice in skip:
-                continue
-            if invoice in to_recreate:
+        for invoice in self.ask.domain_invoices:
+            if invoice in self.ask.recreate_invoices:
                 invoices_recreated.append(invoice.id)
             else:
                 invoices_ignored.append(invoice.id)