Refactor a number of methods in PDFViewerApplication to be async rather than manually returning Promises

*Ignoring whitespace changes is probably necessary, in order for the diff to be readable.*

web/app.js

@@ -133,23 +133,22 @@ let PDFViewerApplication = {
   contentDispositionFilename: null,
 
   // Called once when the document is loaded.
-  initialize(appConfig) {
+  async initialize(appConfig) {
     this.preferences = this.externalServices.createPreferences();
     this.appConfig = appConfig;
 
-    return this._readPreferences().then(() => {
+    await this._readPreferences();
-      return this._parseHashParameters();
+    await this._parseHashParameters();
-    }).then(() => {
+    await this._initializeL10n();
-      return this._initializeL10n();
+
-    }).then(() => {
     if (this.isViewerEmbedded &&
         AppOptions.get('externalLinkTarget') === LinkTarget.NONE) {
       // Prevent external links from "replacing" the viewer,
       // when it's embedded in e.g. an <iframe> or an <object>.
       AppOptions.set('externalLinkTarget', LinkTarget.TOP);
     }
-      return this._initializeViewerComponents();
+    await this._initializeViewerComponents();
-    }).then(() => {
+
     // Bind the various event handlers *after* the viewer has been
     // initialized, to prevent errors if an event arrives too soon.
     this.bindEvents();
@@ -164,13 +163,12 @@ let PDFViewerApplication = {
     });
 
     this.initialized = true;
-    });
   },
 
   /**
    * @private
    */
-  _readPreferences() {
+  async _readPreferences() {
     // A subset of the Preferences that `AppOptions`, for compatibility reasons,
     // is allowed to override if the `AppOptions` values matches the ones below.
     const OVERRIDES = {
@@ -180,24 +178,27 @@ let PDFViewerApplication = {
       textLayerMode: TextLayerMode.DISABLE,
     };
 
-    return this.preferences.getAll().then(function(prefs) {
+    try {
+      const prefs = await this.preferences.getAll();
       for (let name in prefs) {
         if ((name in OVERRIDES) && AppOptions.get(name) === OVERRIDES[name]) {
           continue;
         }
         AppOptions.set(name, prefs[name]);
       }
-    }, function(reason) { });
+    } catch (reason) { }
   },
 
   /**
    * @private
    */
-  _parseHashParameters() {
+  async _parseHashParameters() {
+    if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('PRODUCTION') &&
+        !AppOptions.get('pdfBugEnabled')) {
+      return;
+    }
     const waitOn = [];
 
-    if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION') ||
-        AppOptions.get('pdfBugEnabled')) {
     // Special debugging flags in the hash section of the URL.
     let hash = document.location.hash.substring(1);
     let hashParams = parseQueryString(hash);
@@ -221,15 +222,13 @@ let PDFViewerApplication = {
                      hashParams['disablefontface'] === 'true');
     }
     if ('disablehistory' in hashParams) {
-        AppOptions.set('disableHistory',
+      AppOptions.set('disableHistory', hashParams['disablehistory'] === 'true');
-                       hashParams['disablehistory'] === 'true');
     }
     if ('webgl' in hashParams) {
       AppOptions.set('enableWebGL', hashParams['webgl'] === 'true');
     }
     if ('useonlycsszoom' in hashParams) {
-        AppOptions.set('useOnlyCssZoom',
+      AppOptions.set('useOnlyCssZoom', hashParams['useonlycsszoom'] === 'true');
-                       hashParams['useonlycsszoom'] === 'true');
     }
     if ('verbosity' in hashParams) {
       AppOptions.set('verbosity', hashParams['verbosity'] | 0);
@@ -262,7 +261,6 @@ let PDFViewerApplication = {
          PDFJSDev.test('!PRODUCTION || GENERIC')) && 'locale' in hashParams) {
       AppOptions.set('locale', hashParams['locale']);
     }
-    }
 
     return Promise.all(waitOn);
   },
@@ -270,22 +268,20 @@ let PDFViewerApplication = {
   /**
    * @private
    */
-  _initializeL10n() {
+  async _initializeL10n() {
     this.l10n = this.externalServices.createL10n({
       locale: AppOptions.get('locale'),
     });
-    return this.l10n.getDirection().then((dir) => {
+    const dir = await this.l10n.getDirection();
     document.getElementsByTagName('html')[0].dir = dir;
-    });
   },
 
   /**
    * @private
    */
-  _initializeViewerComponents() {
+  async _initializeViewerComponents() {
-    let { appConfig, } = this;
+    const appConfig = this.appConfig;
 
-    return new Promise((resolve, reject) => {
     this.overlayManager = new OverlayManager();
 
     const dispatchToDOM = AppOptions.get('eventBusDispatchToDOM');
@@ -426,8 +422,6 @@ let PDFViewerApplication = {
 
     this.pdfSidebarResizer = new PDFSidebarResizer(appConfig.sidebarResizer,
                                                    eventBus, this.l10n);
-      resolve(undefined);
-    });
   },
 
   run(config) {
@@ -582,12 +576,12 @@ let PDFViewerApplication = {
    * @returns {Promise} - Returns the promise, which is resolved when all
    *                      destruction is completed.
    */
-  close() {
+  async close() {
     let errorWrapper = this.appConfig.errorWrapper.container;
     errorWrapper.setAttribute('hidden', 'true');
 
     if (!this.pdfLoadingTask) {
-      return Promise.resolve();
+      return;
     }
 
     let promise = this.pdfLoadingTask.destroy();
@@ -632,13 +626,10 @@ let PDFViewerApplication = {
    * @returns {Promise} - Returns the promise, which is resolved when document
    *                      is opened.
    */
-  open(file, args) {
+  async open(file, args) {
     if (this.pdfLoadingTask) {
       // We need to destroy already opened document.
-      return this.close().then(() => {
+      await this.close();
-        // ... and repeat the open() call.
-        return this.open(file, args);
-      });
     }
     // Set the necessary global worker parameters, using the available options.
     const workerParameters = AppOptions.getAll('worker');
@@ -1629,14 +1620,14 @@ function webViewerInitialized() {
     PDFViewerApplication.pdfSidebar.toggle();
   });
 
-  Promise.resolve().then(function() {
+  try {
     webViewerOpenFileViaURL(file);
-  }).catch(function(reason) {
+  } catch (reason) {
     PDFViewerApplication.l10n.get('loading_error', null,
         'An error occurred while loading the PDF.').then((msg) => {
       PDFViewerApplication.error(msg, reason);
     });
-  });
+  }
 }
 
 let webViewerOpenFileViaURL;