IMP account_usability: set sale date on invoice (#101)

* IMP account_usability: set sale date on invoice

account_usability/account.py

@@ -37,6 +37,10 @@ class AccountInvoice(models.Model):
     has_attachment = fields.Boolean(
         compute='_compute_has_attachment',
         search='_search_has_attachment', readonly=True)
+    sale_dates = fields.Char(
+        compute="_compute_sales_dates", readonly=True,
+        help="This information appears on invoice qweb report "
+             "(you may use it for your own report)")
 
     def _compute_has_discount(self):
         prec = self.env['decimal.precision'].precision_get('Discount')
@@ -170,6 +174,24 @@ class AccountInvoice(models.Model):
         # ]
         return res
 
+    def _compute_sales_dates(self):
+        """ French law requires to set sale order dates into invoice
+            returned string: "sale1 (date1), sale2 (date2) ..."
+        """
+        for inv in self:
+            sales = inv.invoice_line_ids.mapped(
+                'sale_line_ids').mapped('order_id')
+            lang = inv.partner_id.commercial_partner_id.lang
+            date_format = self.env["res.lang"]._lang_get(
+                lang or "").date_format
+            dates = ["%s%s" % (
+                     x.name,
+                     x.confirmation_date and " (%s)" %
+                     # only when confirmation_date display it
+                     x.confirmation_date.strftime(date_format) or "")
+                     for x in sales]
+            inv.sale_dates = ", ".join(dates)
+
 
 class AccountInvoiceLine(models.Model):
     _inherit = 'account.invoice.line'