[api-major] Output JavaScript modules in the builds (issue 10317)

At this point in time all browsers, and also Node.js, support standard `import`/`export` statements and we can now finally consider outputting modern JavaScript modules in the builds.[1]

In order for this to work we can *only* use proper `import`/`export` statements throughout the main code-base, and (as expected) our Node.js support made this much more complicated since both the official builds and the GitHub Actions-based tests must keep working.[2]
One remaining issue is that the `pdf.scripting.js` file cannot be built as a JavaScript module, since doing so breaks PDF scripting.

Note that my initial goal was to try and split these changes into a couple of commits, however that unfortunately didn't really work since it turned out to be difficult for smaller patches to work correctly and pass (all) tests that way.[3]
This is a classic case of every change requiring a couple of other changes, with each of those changes requiring further changes in turn and the size/scope quickly increasing as a result.

One possible "issue" with these changes is that we'll now only output JavaScript modules in the builds, which could perhaps be a problem with older tools. However it unfortunately seems far too complicated/time-consuming for us to attempt to support both the old and modern module formats, hence the alternative would be to do "nothing" here and just keep our "old" builds.[4]

---
[1] The final blocker was module support in workers in Firefox, which was implemented in Firefox 114; please see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#browser_compatibility

[2] It's probably possible to further improve/simplify especially the Node.js-specific code, but it does appear to work as-is.

[3] Having partially "broken" patches, that fail tests, as part of the commit history is *really not* a good idea in general.

[4] Outputting JavaScript modules was first requested almost five years ago, see issue 10317, and nowadays there *should* be much better support for JavaScript modules in various tools.

web/app.js

@@ -44,7 +44,6 @@ import {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  loadScript,
   MissingPDFException,
   PDFWorker,
   PromiseCapability,
@@ -2264,10 +2263,10 @@ async function loadFakeWorker() {
   GlobalWorkerOptions.workerSrc ||= AppOptions.get("workerSrc");
 
   if (typeof PDFJSDev === "undefined") {
-    window.pdfjsWorker = await import("pdfjs/pdf.worker.js");
+    globalThis.pdfjsWorker = await import("pdfjs/pdf.worker.js");
     return;
   }
-  await loadScript(PDFWorker.workerSrc);
+  await __non_webpack_import__(PDFWorker.workerSrc); // eslint-disable-line no-undef
 }
 
 async function loadPDFBug(self) {

web/app_options.js

@@ -300,8 +300,8 @@ const defaultOptions = {
       typeof PDFJSDev === "undefined"
         ? "../src/pdf.worker.js"
         : PDFJSDev.test("MOZCENTRAL")
-        ? "resource://pdf.js/build/pdf.worker.js"
-        : "../build/pdf.worker.js",
+        ? "resource://pdf.js/build/pdf.worker.mjs"
+        : "../build/pdf.worker.mjs",
     kind: OptionKind.WORKER,
   },
 };
@@ -325,8 +325,8 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
     /** @type {string} */
     value:
       typeof PDFJSDev === "undefined"
-        ? "../build/dev-sandbox/pdf.sandbox.js"
-        : "../build/pdf.sandbox.js",
+        ? "../build/dev-sandbox/pdf.sandbox.mjs"
+        : "../build/pdf.sandbox.mjs",
     kind: OptionKind.VIEWER,
   };
 } else if (PDFJSDev.test("CHROME")) {

web/generic_scripting.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { getPdfFilenameFromUrl, loadScript } from "pdfjs-lib";
+import { getPdfFilenameFromUrl } from "pdfjs-lib";
 
 async function docProperties(pdfDocument) {
   const url = "",
@@ -41,11 +41,16 @@ async function docProperties(pdfDocument) {
 
 class GenericScripting {
   constructor(sandboxBundleSrc) {
-    this._ready = loadScript(
-      sandboxBundleSrc,
-      /* removeScriptElement = */ true
-    ).then(() => {
-      return window.pdfjsSandbox.QuickJSSandbox();
+    this._ready = new Promise((resolve, reject) => {
+      const sandbox =
+        typeof PDFJSDev === "undefined"
+          ? import(sandboxBundleSrc) // eslint-disable-line no-unsanitized/method
+          : __non_webpack_import__(sandboxBundleSrc); // eslint-disable-line no-undef
+      sandbox
+        .then(pdfjsSandbox => {
+          resolve(pdfjsSandbox.QuickJSSandbox());
+        })
+        .catch(reject);
     });
   }
 

web/pdfjs.js

@@ -35,7 +35,6 @@ const {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  loadScript,
   MissingPDFException,
   noContextMenu,
   normalizeUnicode,
@@ -81,7 +80,6 @@ export {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  loadScript,
   MissingPDFException,
   noContextMenu,
   normalizeUnicode,

web/viewer-geckoview.html

@@ -76,7 +76,7 @@ See https://github.com/adobe-type-tools/cmap-resources
 
     <script src="viewer-geckoview.js" type="module-shim"></script>
 <!--#else-->
-<!--<script src="resource://pdf.js/web/viewer.js"></script>-->
+<!--<script src="resource://pdf.js/web/viewer.mjs" type="module"></script>-->
 <!--#endif-->
 
   </head>

web/viewer-snippet-chrome-extension.html

@@ -1,4 +1,4 @@
 <!-- This snippet is used in the Chromium extension (included from viewer.html) -->
 <base href="/content/web/">
 <link rel="resource" type="application/l10n" href="locale/locale.properties">
-<script src="../build/pdf.js"></script>
+<script src="../build/pdf.mjs" type="module"></script>

web/viewer-snippet-firefox-extension.html

@@ -1,2 +1,2 @@
 <!-- This snippet is used in the Firefox extension (included from viewer.html) -->
-<script src="resource://pdf.js/build/pdf.js"></script>
+<script src="resource://pdf.js/build/pdf.mjs" type="module"></script>

web/viewer-snippet.html

@@ -1,3 +1,3 @@
 <!-- This snippet is used in production (included from viewer.html) -->
 <link rel="resource" type="application/l10n" href="locale/locale.properties">
-<script src="../build/pdf.js"></script>
+<script src="../build/pdf.mjs" type="module"></script>

web/viewer.html

@@ -44,9 +44,9 @@ See https://github.com/adobe-type-tools/cmap-resources
 <!--#endif-->
 
 <!--#if MOZCENTRAL-->
-<!--<script src="resource://pdf.js/web/viewer.js"></script>-->
+<!--<script src="resource://pdf.js/web/viewer.mjs" type="module"></script>-->
 <!--#elif !MOZCENTRAL-->
-<!--<script src="viewer.js"></script>-->
+<!--<script src="viewer.mjs" type="module"></script>-->
 <!--#elif /* Development mode. */-->
     <link rel="resource" type="application/l10n" href="locale/locale.properties">