Swap `config` and `guest` arguments to Sidebar constructor

The `guest` argument is required but the `config` argument is now
optional. Swap them so that required arguments come before optional
ones and set a default value for `config`.

src/annotator/index.js

@@ -48,7 +48,7 @@ const config = configFrom(window);
 function init() {
   const isPDF = typeof window_.PDFViewerApplication !== 'undefined';
 
-  /** @type {(new (e: HTMLElement, config: any, guest: Guest) => Sidebar)|null} */
+  /** @type {(new (e: HTMLElement, guest: Guest, config: Record<string,any>) => Sidebar)|null} */
   let SidebarClass = isPDF ? PdfSidebar : Sidebar;
 
   if (config.subFrameIdentifier) {
@@ -68,7 +68,7 @@ function init() {
 
   const guest = new Guest(document.body, config);
   const sidebar = SidebarClass
-    ? new SidebarClass(document.body, config, guest)
+    ? new SidebarClass(document.body, guest, config)
     : null;
   const notebook = new Notebook(document.body, config);
 

src/annotator/pdf-sidebar.js

@@ -21,11 +21,11 @@ const MIN_PDF_WIDTH = 680;
 export default class PdfSidebar extends Sidebar {
   /**
    * @param {HTMLElement} element
-   * @param {Record<string, any>} config
    * @param {Guest} guest
+   * @param {Record<string, any>} [config]
    */
-  constructor(element, config, guest) {
-    super(element, { ...defaultConfig, ...config }, guest);
+  constructor(element, guest, config = {}) {
+    super(element, guest, { ...defaultConfig, ...config });
 
     this._lastSidebarLayoutState = {
       expanded: false,

src/annotator/sidebar.js

@@ -62,13 +62,13 @@ export default class Sidebar extends Delegator {
    * Create the sidebar iframe, its container and adjacent controls.
    *
    * @param {HTMLElement} element
-   * @param {Record<string, any>} config
    * @param {Guest} guest -
    *   The `Guest` instance for the current frame. It is currently assumed that
    *   it is always possible to annotate in the frame where the sidebar is
    *   displayed.
+   * @param {Record<string, any>} [config]
    */
-  constructor(element, config, guest) {
+  constructor(element, guest, config = {}) {
     super(element, config);
 
     this.iframe = createSidebarIframe(config);

src/annotator/test/pdf-sidebar-test.js

@@ -24,7 +24,7 @@ describe('PdfSidebar', () => {
   const createPdfSidebar = config => {
     const fakeGuest = {};
     const element = document.createElement('div');
-    return new PdfSidebar(element, config, fakeGuest);
+    return new PdfSidebar(element, fakeGuest, config);
   };
 
   let unmockSidebar;

src/annotator/test/sidebar-test.js

@@ -41,7 +41,7 @@ describe('Sidebar', () => {
     document.body.appendChild(container);
     containers.push(container);
 
-    const sidebar = new Sidebar(container, config, fakeGuest);
+    const sidebar = new Sidebar(container, fakeGuest, config);
     sidebars.push(sidebar);
 
     return sidebar;