fix(UX): Optimize rate updation of changing price list

(cherry picked from commit 6087d5a6038d6e636ce1ba006ebd59e820b3cd8e)

erpnext/public/js/controllers/transaction.js

@@ -1586,17 +1586,19 @@ erpnext.TransactionController = class TransactionController extends erpnext.taxe
 		var items_rule_dict = {};
 
 		for(var i=0, l=children.length; i<l; i++) {
-			var d = children[i];
+			var d = children[i] ;
+			let item_row = frappe.get_doc(d.doctype, d.name)
 			var existing_pricing_rule = frappe.model.get_value(d.doctype, d.name, "pricing_rules");
 			for(var k in d) {
 				var v = d[k];
 				if (["doctype", "name"].indexOf(k)===-1) {
 					if(k=="price_list_rate") {
 						if(flt(v) != flt(d.price_list_rate)) price_list_rate_changed = true;
+						item_row['rate'] = v;
 					}
 
 					if (k !== 'free_item_data') {
-						frappe.model.set_value(d.doctype, d.name, k, v);
+						item_row[k] = v;
 					}
 				}
 			}
@@ -1617,6 +1619,7 @@ erpnext.TransactionController = class TransactionController extends erpnext.taxe
 			}
 		}
 
+		me.frm.refresh_field('items');
 		me.apply_rule_on_other_items(items_rule_dict);
 
 		if(!price_list_rate_changed) me.calculate_taxes_and_totals();

erpnext/stock/get_item_details.py

@@ -1097,7 +1097,7 @@ def apply_price_list(args, as_doc=False):
 		}
 
 def apply_price_list_on_item(args):
-	item_doc = frappe.get_doc("Item", args.item_code)
+	item_doc = frappe.db.get_value("Item", args.item_code, ['name', 'variant_of'], as_dict=1)
 	item_details = get_price_list_rate(args, item_doc)
 
 	item_details.update(get_pricing_rule_for_item(args, item_details.price_list_rate))