[FIX] mrp: failing test multi mrp step

It's due to MRP refactoring that confirm raw moves before finished
moves. It implies that in _assign picking, SFP with final product
will search a picking but the stock.move do not have a created_production_id
and it will be merged inside the intermediate SFP (it works before
because it was the intermediate SFP that was merged in the finished SFP).

_key_assign_picking is also added if multiple moves are confirmed w/
and w/h created_production_id, we won't merge them in the same picking.

closes odoo/odoo#36335

Signed-off-by: Christophe Simonis <chs@odoo.com>

addons/mrp/models/stock_move.py

@@ -233,10 +233,13 @@ class StockMove(models.Model):
         res = super(StockMove, self)._should_be_assigned()
         return bool(res and not (self.production_id or self.raw_material_production_id))
 
+    def _key_assign_picking(self):
+        keys = super(StockMove, self)._key_assign_picking()
+        return keys + (self.created_production_id,)
+
     def _search_picking_for_assignation_domain(self):
         res = super(StockMove, self)._search_picking_for_assignation_domain()
-        if self.created_production_id:
-            res.append(('move_lines.created_production_id', '=', self.created_production_id.id))
+        res.append(('move_lines.created_production_id', '=', self.created_production_id.id))
         return res
 
     def _compute_kit_quantities(self, product_id, kit_qty, kit_bom, filters):

addons/mrp/tests/test_warehouse_multistep_manufacturing.py

@@ -165,6 +165,7 @@ class TestMultistepManufacturingWarehouse(TestMrpCommon):
         production_form.product_id = self.complex_product
         production_form.picking_type_id = self.warehouse.manu_type_id
         production = production_form.save()
+        production.action_confirm()
 
         move_raw_ids = production.move_raw_ids
         self.assertEqual(len(move_raw_ids), 2)
@@ -197,23 +198,31 @@ class TestMultistepManufacturingWarehouse(TestMrpCommon):
 
         # Picking: SFP PostProcessing -> Stock
         ## Stick from Subprocess
-        picking = pickings[1]
+        picking = self.env['stock.picking'].search([
+            ('move_lines.product_id', '=', self.finished_product.id),
+            ('location_dest_id', '=', self.warehouse.lot_stock_id.id),
+            ('group_id', '=', production.procurement_group_id.id)
+        ])
         self.assertEqual(len(picking.move_lines), 1)
-        picking.product_id = self.finished_product
 
         # Picking: PC Stock -> Preprocessing
         ## Stick
         ## Raw Iron
-        picking = pickings[0]
+        picking = self.env['stock.picking'].search([
+            ('move_lines.product_id', 'in', [self.finished_product.id, self.raw_product_2.id]),
+            ('location_id', '=', self.warehouse.lot_stock_id.id),
+            ('group_id', '=', production.procurement_group_id.id)
+        ])
         self.assertEqual(len(picking.move_lines), 2)
-        picking.move_lines[0].product_id = self.finished_product
-        picking.move_lines[1].product_id = self.raw_product_2
 
         # Picking: SFP PostProcessing -> Stock
         ## Arrow from this process
-        picking = pickings[2]
+        picking = picking = self.env['stock.picking'].search([
+            ('move_lines.product_id', '=', self.complex_product.id),
+            ('location_dest_id', '=', self.warehouse.lot_stock_id.id),
+            ('group_id', '=', production.procurement_group_id.id)
+        ])
         self.assertEqual(len(picking.move_lines), 1)
-        picking.product_id = self.complex_product
 
 
     def test_manufacturing_flow(self):