[FIX] account, sale: modify invoice

When a user validates an invoice linked to a SO, he might want to modify
it afterwards thanks to the 'Modify' option in the refund wizard. This
will create a refund, reconcile and create a draft invoice.

The issue is that the draft invoice is not linked with the SO.

The fix is to link, in this specific case only, the draft invoice to the
SO. At the same time, we have to make sure to:
- unlink the first invoice (to prevent counting the quantity as invoiced
  in the SO)
- keep track of the first invoice/refund in the invoice list of the SO

opw-673446

addons/account/wizard/account_invoice_refund.py

@@ -87,7 +87,7 @@ class AccountInvoiceRefund(models.TransientModel):
                         invoice = invoice[0]
                         del invoice['id']
                         invoice_lines = inv_line_obj.browse(invoice['invoice_line_ids'])
-                        invoice_lines = inv_obj._refund_cleanup_lines(invoice_lines)
+                        invoice_lines = inv_obj.with_context(mode='modify')._refund_cleanup_lines(invoice_lines)
                         tax_lines = inv_tax_obj.browse(invoice['tax_line_ids'])
                         tax_lines = inv_obj._refund_cleanup_lines(tax_lines)
                         invoice.update({

addons/sale/sale.py

@@ -52,6 +52,9 @@ class SaleOrder(models.Model):
         """
         for order in self:
             invoice_ids = order.order_line.mapped('invoice_lines').mapped('invoice_id')
+            # Search for invoices which have been 'cancelled' (filter_refund = 'modify' in
+            # 'account.invoice.refund')
+            invoice_ids |= invoice_ids.search([('origin', 'like', order.name)])
             # Search for refunds as well
             refund_ids = self.env['account.invoice'].browse()
             if invoice_ids:
@@ -835,6 +838,16 @@ class AccountInvoice(models.Model):
             order.message_post(body=_("Invoice %s paid") % (name))
         return res
 
+    @api.model
+    def _refund_cleanup_lines(self, lines):
+        result = super(AccountInvoice, self)._refund_cleanup_lines(lines)
+        if self.env.context.get('mode') == 'modify':
+            for i in xrange(0, len(lines)):
+                for name, field in lines[i]._fields.iteritems():
+                    if name == 'sale_line_ids':
+                        result[i][2][name] = [(6, 0, lines[i][name].ids)]
+                        lines[i][name] = False
+        return result
 
 class AccountInvoiceLine(models.Model):
     _inherit = 'account.invoice.line'