[FIX] mrp_account: correct component price unbuild

Steps to reproduce:
- Create a component C (automated/FIFO)
- Create and confirm two PO for C
qty: 1, price: 10
qty: 1, price: 20
- Make an MO with C as a component
- Unbuild that MO

Bug:
The valuation of the new component C is wrong, the new move in is valued
at the current product cost instead of its original value.

Fix:
create moves as a return to get the correct value

opw-3379457

closes odoo/odoo#137353

X-original-commit: d42238cc75fe6621c1eb893395856870c8bfbafb
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>

addons/mrp/models/mrp_unbuild.py

@@ -258,6 +258,7 @@ class MrpUnbuild(models.Model):
             'warehouse_id': location_dest_id.warehouse_id.id,
             'unbuild_id': self.id,
             'company_id': move.company_id.id,
+            'origin_returned_move_id': move.id,
         })
 
     def _generate_move_from_bom_line(self, product, product_uom, quantity, bom_line_id=False, byproduct_id=False):

addons/mrp_account/tests/test_valuation_layers.py

@@ -128,6 +128,28 @@ class TestMrpValuationStandard(TestMrpValuationCommon):
         self.assertEqual(self.product1.quantity_svl, 2)
         self.assertEqual(byproduct.quantity_svl, 2)
 
+    def test_fifo_unbuild(self):
+        """ This test creates an MO and then creates an unbuild
+        orders and checks the stock valuation.
+        """
+        self.component.product_tmpl_id.categ_id.property_cost_method = 'fifo'
+        # ---------------------------------------------------
+        #       MO
+        # ---------------------------------------------------
+        self._make_in_move(self.component, 1, 10)
+        self._make_in_move(self.component, 1, 20)
+        mo = self._make_mo(self.bom, 1)
+        self._produce(mo)
+        mo.button_mark_done()
+        self.assertEqual(self.component.value_svl, 20)
+        # ---------------------------------------------------
+        #       Unbuild
+        # ---------------------------------------------------
+        unbuild_form = Form(self.env['mrp.unbuild'])
+        unbuild_form.mo_id = mo
+        unbuild_form.save().action_unbuild()
+        self.assertEqual(self.component.value_svl, 30)
+
     def test_fifo_avco_1(self):
         self.component.product_tmpl_id.categ_id.property_cost_method = 'fifo'
         self.product1.product_tmpl_id.categ_id.property_cost_method = 'average'