[FIX] purchase: set all dates and not-stored field (9.0 only)

The feature "set all date to all order line" on a purchase order allow
user to update the schedulded date of all order lines.

It was backported in 9.0 with 401a3cfa but in 9.0 date_planned was not
stored, the button would wrongly set the scheduled dates of the lines to
the minimum date.

With this commit the functionality should work as expected, unless
someone use an out-of-date template in which case the functionnality is
disabled.

opw-697680

note: PO date_planned is stored after 9.0 so this commit must not be
forward-ported.

addons/purchase/purchase.py

@@ -441,10 +441,13 @@ class PurchaseOrder(models.Model):
 
     @api.multi
     def action_set_date_planned(self):
+        # implementation for 9.0 where PO date_planned is not stored
+        date_planned = self.env.context.get('date_planned')
+        if not date_planned:
+            return
         for order in self:
-            #DO NOT FORWARD PORT
             for line in order.order_line:
-                line.update({'date_planned': order.date_planned})
+                line.update({'date_planned': date_planned})
 
 
 class PurchaseOrderLine(models.Model):

addons/purchase/purchase_view.xml

@@ -252,7 +252,7 @@
                                     <label for="date_planned"/>
                                     <div>
                                         <field name="date_planned" required="1" attrs="{'readonly': [('state', 'not in', ('draft', 'sent'))]}"/>
-                                        <button name="action_set_date_planned" type="object"
+                                        <button name="action_set_date_planned" context="{'date_planned': date_planned}" type="object"
                                             states="draft,sent"
                                             string="Set date to all order lines"
                                             help="This changes the scheduled date of all order lines to the given date"