wait for trigger promises to finish before save (#4488)

frappe/public/js/legacy/form.js

@@ -205,7 +205,11 @@ _f.Frm.prototype.watch_model_updates = function() {
 				&& me.fields_dict[fieldname].refresh(fieldname);
 
 			me.layout.refresh_dependency();
-			return me.script_manager.trigger(fieldname, doc.doctype, doc.name);
+			let object = me.script_manager.trigger(fieldname, doc.doctype, doc.name);
+			if(object instanceof Promise) {
+				me.promises.push(object);
+			}
+			return object;
 		}
 	});
 
@@ -586,6 +590,8 @@ _f.Frm.prototype.setnewdoc = function() {
 	// this.check_doctype_conflict(docname);
 	var me = this;
 
+	this.promises = [];
+
 	// hide any open grid
 	this.script_manager.trigger("before_load", this.doctype, this.docname)
 		.then(() => {
@@ -696,7 +702,9 @@ _f.Frm.prototype.save = function(save_action, callback, btn, on_error) {
 
 		// let any pending js process finish
 		setTimeout(function() {
-			me._save(save_action, callback, btn, on_error, resolve);
+			Promise.all(me.promises).then(() => {
+				me._save(save_action, callback, btn, on_error, resolve);
+			});
 		}, 100);
 	});
 };