Reduce usage of SystemJS, in the development viewer, even further

With these changes SystemJS is now only used, during development, on the worker-thread and in the unit/font-tests, since Firefox is currently missing support for worker modules; please see https://bugzilla.mozilla.org/show_bug.cgi?id=1247687

Hence all the JavaScript files in the `web/` and `src/display/` folders are now loaded *natively* by the browser (during development) using standard `import` statements/calls, thanks to a nice `import-maps` polyfill.

*Please note:* As soon as https://bugzilla.mozilla.org/show_bug.cgi?id=1247687 is fixed in Firefox, we should be able to remove all traces of SystemJS and thus finally be able to use every possible modern JavaScript feature.

.eslintrc

@@ -1,6 +1,6 @@
 {
  "parserOptions": {
- "ecmaVersion": 8,
+ "ecmaVersion": 2020,
  "sourceType": "module",
  },
 
@@ -17,13 +17,12 @@
 
  "env": {
  "browser": true,
- "es6": true,
+ "es2020": true,
  "worker": true,
  "amd": true,
  },
 
  "globals": {
- "globalThis": false,
  "PDFJSDev": false,
  "exports": false,
  "SystemJS": false,

external/builder/preprocessor2.js

@@ -322,7 +322,7 @@ function preprocessPDFJSCode(ctx, code) {
  },
  };
  var parseOptions = {
- ecmaVersion: 8,
+ ecmaVersion: 2020,
  locations: true,
  sourceFile: ctx.sourceFile,
  sourceType: "module",

package.json

@@ -23,6 +23,7 @@
  "eslint-plugin-no-unsanitized": "^3.1.1",
  "eslint-plugin-prettier": "^3.1.3",
  "eslint-plugin-unicorn": "^20.0.0",
+ "es-module-shims": "^0.4.6",
  "fancy-log": "^1.3.3",
  "globals": "^11.12.0",
  "gulp": "^4.0.2",

src/core/.eslintrc

@@ -0,0 +1,13 @@
+{
+ "parserOptions": {
+ "ecmaVersion": 2017,
+ },
+
+ "extends": [
+ "../../.eslintrc"
+ ],
+
+ "env": {
+ "es2017": true,
+ },
+}

src/display/api.js

@@ -1650,7 +1650,9 @@ const PDFWorker = (function PDFWorkerClosure() {
  }
  if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
  if (typeof SystemJS !== "object") {
- throw new Error("SystemJS must be used to load fake worker.");
+ // Manually load SystemJS, since it's only necessary for fake workers.
+ await loadScript("../node_modules/systemjs/dist/system.js");
+ await loadScript("../systemjs.config.js");
  }
  const worker = await SystemJS.import("pdfjs/core/worker.js");
  return worker.WorkerMessageHandler;

src/pdf.js

@@ -77,8 +77,8 @@ const pdfjsDisplayAPICompatibility = require("./display/api_compatibility.js");
 >>>>>>> Re-factor `setPDFNetworkStreamFactory`, in src/display/api.js, to also accept an asynchronous function
 if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
  const streamsPromise = Promise.all([
- SystemJS.import("pdfjs/display/network.js"),
- SystemJS.import("pdfjs/display/fetch_stream.js"),
+ import("pdfjs/display/network.js"),
+ import("pdfjs/display/fetch_stream.js"),
  ]);
 <<<<<<< HEAD
  setPDFNetworkStreamFactory(params => {

web/app.js

@@ -1833,7 +1833,9 @@ async function loadFakeWorker() {
  }
  if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
  if (typeof SystemJS !== "object") {
- throw new Error("SystemJS must be used to load fake worker.");
+ // Manually load SystemJS, since it's only necessary for fake workers.
+ await loadScript("../node_modules/systemjs/dist/system.js");
+ await loadScript("../systemjs.config.js");
  }
  window.pdfjsWorker = await SystemJS.import("pdfjs/core/worker.js");
  return undefined;

web/viewer.html

@@ -45,16 +45,26 @@
 <!--#endif-->
 
 <!--#if !PRODUCTION-->
- <script src="../node_modules/systemjs/dist/system.js"></script>
- <script src="../systemjs.config.js"></script>
+ <script defer src="../node_modules/es-module-shims/dist/es-module-shims.js"></script>
+ <script type="importmap-shim">
+ {
+ "imports": {
+ "pdfjs/": "../src/",
+ "pdfjs-lib": "../src/pdf.js",
+ "pdfjs-web/": "./"
+ }
+ }
+ </script>
+
+ <script src="viewer.js" type="module-shim"></script>
 <!--#endif-->
 
 <!--#if (GENERIC && !MINIFIED) -->
 <!--#include viewer-snippet.html-->
 <!--#endif-->
 
 <!--#if !MINIFIED -->
- <script src="viewer.js"></script>
+<!--<script src="viewer.js"></script>-->
 <!--#else-->
 <!--#include viewer-snippet-minified.html-->
 <!--#endif-->

web/viewer.js

@@ -189,11 +189,11 @@ function webViewerLoad() {
  const config = getViewerConfiguration();
  if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
  Promise.all([
- SystemJS.import("pdfjs-web/app.js"),
- SystemJS.import("pdfjs-web/app_options.js"),
- SystemJS.import("pdfjs-web/genericcom.js"),
- SystemJS.import("pdfjs-web/pdf_print_service.js"),
- ]).then(function ([app, appOptions, ...otherModules]) {
+ import("pdfjs-web/app.js"),
+ import("pdfjs-web/app_options.js"),
+ import("pdfjs-web/genericcom.js"),
+ import("pdfjs-web/pdf_print_service.js"),
+ ]).then(function ([app, appOptions, genericCom, pdfPrintService]) {
  window.PDFViewerApplication = app.PDFViewerApplication;
  window.PDFViewerApplicationOptions = appOptions.AppOptions;
  app.PDFViewerApplication.run(config);