[FIX] stock: user-default picking return

- Activate Developer mode
- Go to Settings / Technical / Actions / User-defined Defaults
- Create the following:
  Field: To Refund (update SO/PO) (stock.return.picking.line)
  Default Value (JSON format): true
- Create a SO with a product invoiced based on delivered quantity
- Validate the SO, validate the picking
- Return the picking

The field 'To Refund (update SO/PO)' is is not, while it should be.

This is because we don't explicitly call the `default_get`, therefore
only rely on the default value of the field.

opw-2172513

closes odoo/odoo#45235

X-original-commit: 70d6f25b83f962d91243edaa0ff8e9a78b2e18ac
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/stock/wizard/stock_picking_return.py

@@ -49,6 +49,10 @@ class ReturnPicking(models.TransientModel):
         product_return_moves = [(5,)]
         if self.picking_id and self.picking_id.state != 'done':
             raise UserError(_("You may only return Done pickings."))
+        # In case we want to set specific default values (e.g. 'to_refund'), we must fetch the
+        # default values for creation.
+        line_fields = [f for f in self.env['stock.return.picking.line']._fields.keys()]
+        product_return_moves_data_tmpl = self.env['stock.return.picking.line'].default_get(line_fields)
         for move in self.picking_id.move_lines:
             if move.state == 'cancel':
                 continue
@@ -56,7 +60,9 @@ class ReturnPicking(models.TransientModel):
                 continue
             if move.move_dest_ids:
                 move_dest_exists = True
-            product_return_moves.append((0, 0, self._prepare_stock_return_picking_line_vals_from_move(move)))
+            product_return_moves_data = dict(product_return_moves_data_tmpl)
+            product_return_moves_data.update(self._prepare_stock_return_picking_line_vals_from_move(move))
+            product_return_moves.append((0, 0, product_return_moves_data))
         if self.picking_id and not product_return_moves:
             raise UserError(_("No products to return (only lines in Done state and not fully returned yet can be returned)."))
         if self.picking_id: