linting, use emptyObject for serializers

packages/base/src/widget.ts

@@ -9,7 +9,7 @@ import $ from 'jquery';
 
 import { NativeView } from './nativeview';
 
-import { JSONObject, JSONValue } from '@lumino/coreutils';
+import { JSONObject, JSONValue, JSONExt } from '@lumino/coreutils';
 
 import { Message, MessageLoop } from '@lumino/messaging';
 
@@ -37,7 +37,8 @@ const IPY_MODEL_ = 'IPY_MODEL_';
 /**
  * A best-effort method for performing deep copies.
  */
-const deepcopy = globalThis.structuredClone || ((x: any) => JSON.parse(JSON.stringify(x)));
+const deepcopy =
+  globalThis.structuredClone || ((x: any) => JSON.parse(JSON.stringify(x)));
 
 /**
  * Replace model ids with models recursively.
@@ -48,13 +49,13 @@ export function unpack_models(
 ): Promise<WidgetModel | Dict<WidgetModel> | WidgetModel[] | any> {
   if (Array.isArray(value)) {
     const unpacked: any[] = [];
-    for(const sub_value of value) {
+    for (const sub_value of value) {
       unpacked.push(unpack_models(sub_value, manager));
     }
     return Promise.all(unpacked);
   } else if (value instanceof Object && typeof value !== 'string') {
     const unpacked: { [key: string]: any } = {};
-    for(const [key, sub_value] of Object.entries(value)) {
+    for (const [key, sub_value] of Object.entries(value)) {
       unpacked[key] = unpack_models(sub_value, manager);
     }
     return utils.resolvePromisesDict(unpacked);
@@ -70,22 +71,22 @@ export function unpack_models(
  *
  * If the commonly-used `unpack_models` is given as the `seralize` method,
  * and no `deserialize` is given, this will be used as a default.
-*/
+ */
 export function pack_models(
   value: WidgetModel | Dict<WidgetModel> | WidgetModel[] | any,
   widget?: WidgetModel
 ): any | Dict<unknown> | string | (Dict<unknown> | string)[] {
   if (Array.isArray(value)) {
     const model_ids: string[] = [];
-    for(const model of value) {
+    for (const model of value) {
       model_ids.push(pack_models(model, widget));
     }
     return model_ids;
   } else if (value instanceof WidgetModel) {
     return `${IPY_MODEL_}${value.model_id}`;
-  } else if (value instanceof Object && typeof value !== 'string' ) {
+  } else if (value instanceof Object && typeof value !== 'string') {
     const packed: { [key: string]: string } = {};
-    for(const [key, sub_value] of Object.entries(value)) {
+    for (const [key, sub_value] of Object.entries(value)) {
       packed[key] = pack_models(sub_value, widget);
     }
   } else {
@@ -565,7 +566,7 @@ export class WidgetModel extends Backbone.Model {
       (this.constructor as typeof WidgetModel).serializers || {};
     for (const k of Object.keys(state)) {
       try {
-        let { serialize, deserialize } = serializers[k];
+        let { serialize, deserialize } = serializers[k] || JSONExt.emptyObject;
 
         if (serialize == null && deserialize === unpack_models) {
           // handle https://github.com/jupyter-widgets/ipywidgets/issues/3735