[FIX] sale_mrp: MO link missing with 3steps manufacture

- Storable product with MTO and manufacture route;
- On your warehouse set 3 steps manufacture
- Create a SO for this product > Confirm

The smart button linking the Manufacturing order does not appear on
the MO.

opw-2634309

closes odoo/odoo#76485

Signed-off-by: Rémy Voet <ryv-odoo@users.noreply.github.com>
Co-authored-by: Arnold Moyaux <arm@odoo.com>

addons/mrp/models/stock_rule.py

@@ -89,7 +89,11 @@ class StockRule(models.Model):
                 # Create now the procurement group that will be assigned to the new MO
                 # This ensure that the outgoing move PostProduction -> Stock is linked to its MO
                 # rather than the original record (MO or SO)
-                procurement.values['group_id'] = self.env["procurement.group"].create({'name': name})
+                group = procurement.values.get('group_id')
+                if group:
+                    procurement.values['group_id'] = group.copy({'name': name})
+                else:
+                    procurement.values['group_id'] = self.env["procurement.group"].create({'name': name})
         return super()._run_pull(procurements)
 
     def _get_custom_move_fields(self):

addons/sale_mrp/models/sale.py

@@ -14,12 +14,16 @@ class SaleOrder(models.Model):
 
     @api.depends('procurement_group_id.stock_move_ids.created_production_id.procurement_group_id.mrp_production_ids')
     def _compute_mrp_production_count(self):
+        data = self.env['procurement.group'].read_group([('sale_id', 'in', self.ids), ('mrp_production_ids', '!=', False)], ['id'], ['sale_id'])
+        mrp_count = dict()
+        for item in data:
+            mrp_count[item['sale_id'][0]] = item['sale_id_count']
         for sale in self:
-            sale.mrp_production_count = len(sale.procurement_group_id.stock_move_ids.created_production_id.procurement_group_id.mrp_production_ids)
+            sale.mrp_production_count = mrp_count.get(sale.id)
 
     def action_view_mrp_production(self):
         self.ensure_one()
-        mrp_production_ids = self.procurement_group_id.stock_move_ids.created_production_id.procurement_group_id.mrp_production_ids.ids
+        mrp_production_ids = self.env['mrp.production'].search([('procurement_group_id.sale_id', '=', self.id)]).ids
         action = {
             'res_model': 'mrp.production',
             'type': 'ir.actions.act_window',