Move, and modernize, Util.loadScript from src/shared/util.js to src/display/dom_utils.js

Not only is the `Util.loadScript` helper function unused on the Worker side, even trying to use it there would throw an Error (since `document` isn't defined/available in Workers).
Hence this helper function is moved, and its code modernized slightly by having it return a Promise rather than needing a callback function.

Finally, to reduced code duplication, the "new" loadScript function is exported and used in the viewer.

src/display/api.js

@@ -21,8 +21,8 @@ import {
   UnexpectedResponseException, UnknownErrorException, unreachable, Util, warn
 } from '../shared/util';
 import {
-  DOMCanvasFactory, DOMCMapReaderFactory, DummyStatTimer, PageViewport,
-  RenderingCancelledException, StatTimer
+  DOMCanvasFactory, DOMCMapReaderFactory, DummyStatTimer, loadScript,
+  PageViewport, RenderingCancelledException, StatTimer
 } from './dom_utils';
 import { FontFaceObject, FontLoader } from './font_loader';
 import { apiCompatibilityParams } from './api_compatibility';
@@ -1356,7 +1356,7 @@ var PDFWorker = (function PDFWorkerClosure() {
       }
     } else {
       let loader = fakeWorkerFilesLoader || function(callback) {
-        Util.loadScript(getWorkerSrc(), function() {
+        loadScript(getWorkerSrc()).then(function() {
           callback(window.pdfjsWorker.WorkerMessageHandler);
         });
       };

src/display/dom_utils.js

@@ -428,6 +428,19 @@ class DummyStatTimer {
   }
 }
 
+function loadScript(src) {
+  return new Promise((resolve, reject) => {
+    let script = document.createElement('script');
+    script.src = src;
+
+    script.onload = resolve;
+    script.onerror = function() {
+      reject(new Error(`Cannot load script at: ${script.src}`));
+    };
+    (document.head || document.documentElement).appendChild(script);
+  });
+}
+
 export {
   PageViewport,
   RenderingCancelledException,
@@ -440,4 +453,5 @@ export {
   DOMSVGFactory,
   StatTimer,
   DummyStatTimer,
+  loadScript,
 };

src/pdf.js

@@ -108,6 +108,7 @@ exports.RenderingCancelledException =
 exports.getFilenameFromUrl = pdfjsDisplayDOMUtils.getFilenameFromUrl;
 exports.LinkTarget = pdfjsDisplayDOMUtils.LinkTarget;
 exports.addLinkAttributes = pdfjsDisplayDOMUtils.addLinkAttributes;
+exports.loadScript = pdfjsDisplayDOMUtils.loadScript;
 exports.GlobalWorkerOptions = pdfjsDisplayWorkerOptions.GlobalWorkerOptions;
 exports.apiCompatibilityParams =
   pdfjsDisplayAPICompatibility.apiCompatibilityParams;

src/shared/util.js

@@ -908,21 +908,6 @@ var Util = (function UtilClosure() {
     }
   };
 
-  Util.loadScript = function Util_loadScript(src, callback) {
-    var script = document.createElement('script');
-    var loaded = false;
-    script.setAttribute('src', src);
-    if (callback) {
-      script.onload = function() {
-        if (!loaded) {
-          callback();
-        }
-        loaded = true;
-      };
-    }
-    document.getElementsByTagName('head')[0].appendChild(script);
-  };
-
   return Util;
 })();
 

web/app.js

@@ -22,8 +22,8 @@ import {
 } from './ui_utils';
 import {
   build, createBlob, getDocument, getFilenameFromUrl, GlobalWorkerOptions,
-  InvalidPDFException, LinkTarget, MissingPDFException, OPS, PDFWorker, shadow,
-  UnexpectedResponseException, UNSUPPORTED_FEATURES, version
+  InvalidPDFException, LinkTarget, loadScript, MissingPDFException, OPS,
+  PDFWorker, shadow, UnexpectedResponseException, UNSUPPORTED_FEATURES, version
 } from 'pdfjs-lib';
 import { CursorTool, PDFCursorTools } from './pdf_cursor_tools';
 import { PDFRenderingQueue, RenderingStates } from './pdf_rendering_queue';
@@ -1551,11 +1551,11 @@ if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
 }
 
 function loadFakeWorker() {
-  return new Promise(function(resolve, reject) {
-    if (!GlobalWorkerOptions.workerSrc) {
-      GlobalWorkerOptions.workerSrc = AppOptions.get('workerSrc');
-    }
-    if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION')) {
+  if (!GlobalWorkerOptions.workerSrc) {
+    GlobalWorkerOptions.workerSrc = AppOptions.get('workerSrc');
+  }
+  if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION')) {
+    return new Promise(function(resolve, reject) {
       if (typeof SystemJS === 'object') {
         SystemJS.import('pdfjs/core/worker').then((worker) => {
           window.pdfjsWorker = worker;
@@ -1568,37 +1568,18 @@ function loadFakeWorker() {
         reject(new Error(
           'SystemJS or CommonJS must be used to load fake worker.'));
       }
-    } else {
-      let script = document.createElement('script');
-      script.src = PDFWorker.getWorkerSrc();
-      script.onload = function() {
-        resolve();
-      };
-      script.onerror = function() {
-        reject(new Error(`Cannot load fake worker at: ${script.src}`));
-      };
-      (document.head || document.documentElement).appendChild(script);
-    }
-  });
+    });
+  }
+  return loadScript(PDFWorker.getWorkerSrc());
 }
 
 function loadAndEnablePDFBug(enabledTabs) {
-  return new Promise(function (resolve, reject) {
-    let appConfig = PDFViewerApplication.appConfig;
-    let script = document.createElement('script');
-    script.src = appConfig.debuggerScriptPath;
-    script.onload = function () {
-      PDFBug.enable(enabledTabs);
-      PDFBug.init({
-        OPS,
-      }, appConfig.mainContainer);
-      resolve();
-    };
-    script.onerror = function () {
-      reject(new Error('Cannot load debugger at ' + script.src));
-    };
-    (document.getElementsByTagName('head')[0] || document.body).
-      appendChild(script);
+  let appConfig = PDFViewerApplication.appConfig;
+  return loadScript(appConfig.debuggerScriptPath).then(function() {
+    PDFBug.enable(enabledTabs);
+    PDFBug.init({
+      OPS,
+    }, appConfig.mainContainer);
   });
 }