[FIX] mrp_subcontracting: allow to return to subcontractor

addons/mrp_subcontracting/wizard/stock_picking_return.py

@@ -1,14 +1,30 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import models
-
+from odoo import api, models
+from odoo.osv.expression import OR
 
 class ReturnPicking(models.TransientModel):
     _inherit = 'stock.return.picking'
 
+    @api.onchange('picking_id')
+    def _onchange_picking_id(self):
+        res = super(ReturnPicking, self)._onchange_picking_id()
+        if not any(self.product_return_moves.filtered(lambda r: r.quantity > 0).move_id.mapped('is_subcontract')):
+            return res
+        subcontract_location = self.picking_id.partner_id.property_stock_subcontractor
+        self.location_id = subcontract_location.id
+        domain_location = OR([
+            ['|', ('id', '=', self.original_location_id.id), ('return_location', '=', True)],
+            [('id', '=', subcontract_location.id)]
+        ])
+        if not res:
+            res = {'domain': {'location_id': domain_location}}
+        else:
+            res['domain'] = {'location_id': domain_location}
+        return res
+
     def _prepare_move_default_values(self, return_line, new_picking):
         vals = super(ReturnPicking, self)._prepare_move_default_values(return_line, new_picking)
-        if return_line.move_id.is_subcontract:
-            vals['location_dest_id'] = self.picking_id.partner_id.property_stock_subcontractor.id
+        vals['is_subcontract'] = False
         return vals

addons/stock/wizard/stock_picking_return_views.xml

@@ -10,7 +10,7 @@
         <field name="arch" type="xml">
             <form>
                 <field name="move_dest_exists" invisible="1"/>
-                <field name="picking_id" invisible="1"/>
+                <field name="picking_id" invisible="1" force_save="1"/>
                 <group attrs="{'invisible': [('move_dest_exists', '=', False)]}">
                     <div class="oe_grey">
                         <p>This picking appears to be chained with another operation. Later, if you receive the goods you are returning now, make sure to <b>reverse</b> the returned picking in order to avoid logistic rules to be applied again (which would create duplicated operations)</p>