Ensure that GenericL10n works if the locale files cannot be loaded

 - Ensure that localization works in the GENERIC viewer, even if the necessary locale files cannot be loaded.
   This was the behaviour prior to the introduction of Fluent, and it seems worthwhile to keep that (especially since we already bundle the en-US strings anyway).

 - Let the `GenericL10n`-implementation use the *bundled* en-US strings directly when no language is provided.

 - Remove the `NullL10n`-implementation, and simply fallback to `GenericL10n`, to reduce the maintenance burden of viewer-components localization.

 - Indirectly, given the previous point, stop exporting `NullL10n` in the viewer-components since it's now removed.
   Note that it was never really intended to be used directly and only existed as a fallback.

*Please note:* This doesn't affect the Firefox PDF Viewer, thanks to the use of import maps.

examples/mobile-viewer/viewer.mjs

@@ -272,7 +272,7 @@ const PDFViewerApplication = {
     });
     this.pdfLinkService = linkService;
 
-    this.l10n = pdfjsViewer.NullL10n;
+    this.l10n = new pdfjsViewer.GenericL10n();
 
     const container = document.getElementById("viewerContainer");
     const pdfViewer = new pdfjsViewer.PDFViewer({

gulpfile.mjs

@@ -272,7 +272,7 @@ function createWebpackConfig(
     "web-com": "",
     "web-download_manager": "",
     "web-external_services": "",
-    "web-l10n_utils": "web/stubs.js",
+    "web-null_l10n": "",
     "web-pdf_attachment_viewer": "web/pdf_attachment_viewer.js",
     "web-pdf_cursor_tools": "web/pdf_cursor_tools.js",
     "web-pdf_document_properties": "web/pdf_document_properties.js",
@@ -294,6 +294,7 @@ function createWebpackConfig(
     viewerAlias["web-com"] = "web/chromecom.js";
     viewerAlias["web-download_manager"] = "web/download_manager.js";
     viewerAlias["web-external_services"] = "web/chromecom.js";
+    viewerAlias["web-null_l10n"] = "web/l10n.js";
     viewerAlias["web-preferences"] = "web/chromecom.js";
     viewerAlias["web-print_service"] = "web/pdf_print_service.js";
   } else if (bundleDefines.GENERIC) {
@@ -308,13 +309,12 @@ function createWebpackConfig(
     viewerAlias["web-com"] = "web/genericcom.js";
     viewerAlias["web-download_manager"] = "web/download_manager.js";
     viewerAlias["web-external_services"] = "web/genericcom.js";
-    viewerAlias["web-l10n_utils"] = "web/l10n_utils.js";
+    viewerAlias["web-null_l10n"] = "web/genericl10n.js";
     viewerAlias["web-preferences"] = "web/genericcom.js";
     viewerAlias["web-print_service"] = "web/pdf_print_service.js";
   } else if (bundleDefines.MOZCENTRAL) {
     if (bundleDefines.GECKOVIEW) {
       const gvAlias = {
-        "web-l10n_utils": "web/stubs.js",
         "web-toolbar": "web/toolbar-geckoview.js",
       };
       for (const key in viewerAlias) {
@@ -324,6 +324,7 @@ function createWebpackConfig(
     viewerAlias["web-com"] = "web/firefoxcom.js";
     viewerAlias["web-download_manager"] = "web/firefoxcom.js";
     viewerAlias["web-external_services"] = "web/firefoxcom.js";
+    viewerAlias["web-null_l10n"] = "web/l10n.js";
     viewerAlias["web-preferences"] = "web/firefoxcom.js";
     viewerAlias["web-print_service"] = "web/firefox_print_service.js";
   }
@@ -1616,7 +1617,7 @@ function buildLibHelper(bundleDefines, inputStream, outputDir) {
       "display-node_utils": "./node_utils.js",
       "fluent-bundle": "../../../node_modules/@fluent/bundle/esm/index.js",
       "fluent-dom": "../../../node_modules/@fluent/dom/esm/index.js",
-      "web-l10n_utils": "../web/l10n_utils.js",
+      "web-null_l10n": "../web/genericl10n.js",
     },
   };
   const licenseHeaderLibre = fs

test/unit/pdf_viewer.component_spec.js

@@ -30,8 +30,6 @@ import { AnnotationLayerBuilder } from "../../web/annotation_layer_builder.js";
 import { DownloadManager } from "../../web/download_manager.js";
 import { EventBus } from "../../web/event_utils.js";
 import { GenericL10n } from "../../web/genericl10n.js";
-import { L10n } from "../../web/l10n.js";
-import { NullL10n } from "../../web/l10n_utils.js";
 import { PDFHistory } from "../../web/pdf_history.js";
 import { PDFPageView } from "../../web/pdf_page_view.js";
 import { PDFScriptingManager } from "../../web/pdf_scripting_manager.component.js";
@@ -54,7 +52,6 @@ describe("pdfviewer_api", function () {
       FindState,
       GenericL10n,
       LinkTarget,
-      NullL10n,
       parseQueryString,
       PDFFindController,
       PDFHistory,
@@ -73,14 +70,4 @@ describe("pdfviewer_api", function () {
       XfaLayerBuilder,
     });
   });
-
-  it("checks that `NullL10n` implements all methods", function () {
-    const methods = Object.getOwnPropertyNames(NullL10n).sort();
-
-    const baseMethods = Object.getOwnPropertyNames(L10n.prototype)
-      .filter(m => m !== "constructor" && !m.startsWith("_"))
-      .sort();
-
-    expect(methods).toEqual(baseMethods);
-  });
 });

test/unit/unit_test.html

@@ -30,7 +30,7 @@
         "web-com": "../../web/genericcom.js",
         "web-download_manager": "../../web/download_manager.js",
         "web-external_services": "../../web/genericcom.js",
-        "web-l10n_utils": "../../web/l10n_utils.js",
+        "web-null_l10n": "../../web/genericl10n.js",
         "web-pdf_attachment_viewer": "../../web/pdf_attachment_viewer.js",
         "web-pdf_cursor_tools": "../../web/pdf_cursor_tools.js",
         "web-pdf_document_properties": "../../web/pdf_document_properties.js",

tsconfig.json

@@ -16,7 +16,7 @@
       "display-node_utils": ["./src/display/node_utils"],
       "fluent-bundle": ["./node_modules/@fluent/bundle/esm/index.js"],
       "fluent-dom": ["./node_modules/@fluent/dom/esm/index.js"],
-      "web-l10n_utils": ["./web/l10n_utils"]
+      "web-null_l10n": ["../web/genericl10n.js"]
     }
   },
   "files": ["src/pdf.js", "web/pdf_viewer.component.js"]

web/annotation_editor_layer_builder.js

@@ -25,7 +25,7 @@
 /** @typedef {import("../src/display/annotation_layer.js").AnnotationLayer} AnnotationLayer */
 
 import { AnnotationEditorLayer } from "pdfjs-lib";
-import { NullL10n } from "web-l10n_utils";
+import { GenericL10n } from "web-null_l10n";
 
 /**
  * @typedef {Object} AnnotationEditorLayerBuilderOptions
@@ -55,7 +55,10 @@ class AnnotationEditorLayerBuilder {
     this.pageDiv = options.pageDiv;
     this.pdfPage = options.pdfPage;
     this.accessibilityManager = options.accessibilityManager;
-    this.l10n = options.l10n || NullL10n;
+    this.l10n = options.l10n;
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
+      this.l10n ||= new GenericL10n();
+    }
     this.annotationEditorLayer = null;
     this.div = null;
     this._cancelled = false;

web/genericl10n.js

@@ -20,22 +20,34 @@ import { DOMLocalization } from "fluent-dom";
 import { fetchData } from "pdfjs-lib";
 import { L10n } from "./l10n.js";
 
+function createBundle(lang, text) {
+  const resource = new FluentResource(text);
+  const bundle = new FluentBundle(lang);
+  const errors = bundle.addResource(resource);
+  if (errors.length) {
+    console.error("L10n errors", errors);
+  }
+  return bundle;
+}
+
 /**
  * @implements {IL10n}
  */
 class GenericL10n extends L10n {
   constructor(lang) {
     super({ lang });
-    this._setL10n(
-      new DOMLocalization(
-        [],
-        GenericL10n.#generateBundles.bind(
+
+    const generateBundles = !lang
+      ? GenericL10n.#generateBundlesFallback.bind(
           GenericL10n,
-          "en-us",
           this.getLanguage()
         )
-      )
-    );
+      : GenericL10n.#generateBundles.bind(
+          GenericL10n,
+          "en-us",
+          this.getLanguage()
+        );
+    this._setL10n(new DOMLocalization([], generateBundles));
   }
 
   /**
@@ -63,6 +75,9 @@ class GenericL10n extends L10n {
       if (bundle) {
         yield bundle;
       }
+      if (lang === "en-us") {
+        yield this.#createBundleFallback(lang);
+      }
     }
   }
 
@@ -74,20 +89,36 @@ class GenericL10n extends L10n {
     const url = new URL(path, baseURL);
     const text = await fetchData(url, /* type = */ "text");
 
-    const resource = new FluentResource(text);
-    const bundle = new FluentBundle(lang);
-    const errors = bundle.addResource(resource);
-    if (errors.length) {
-      console.error("L10n errors", errors);
-    }
-    return bundle;
+    return createBundle(lang, text);
   }
 
   static async #getPaths() {
-    const { href } = document.querySelector(`link[type="application/l10n"]`);
-    const paths = await fetchData(href, /* type = */ "json");
+    try {
+      const { href } = document.querySelector(`link[type="application/l10n"]`);
+      const paths = await fetchData(href, /* type = */ "json");
+
+      return { baseURL: href.replace(/[^/]*$/, "") || "./", paths };
+    } catch {}
+    return { baseURL: "./", paths: Object.create(null) };
+  }
+
+  static async *#generateBundlesFallback(lang) {
+    yield this.#createBundleFallback(lang);
+  }
+
+  static async #createBundleFallback(lang) {
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("TESTING")) {
+      throw new Error("Not implemented: #createBundleFallback");
+    }
+    const text =
+      typeof PDFJSDev === "undefined"
+        ? await fetchData(
+            new URL(`./locale/${lang}/viewer.ftl`, window.location.href),
+            /* type = */ "text"
+          )
+        : PDFJSDev.eval("DEFAULT_FTL");
 
-    return { baseURL: href.replace(/[^/]*$/, "") || "./", paths };
+    return createBundle(lang, text);
   }
 }
 

web/l10n.js

@@ -117,4 +117,6 @@ class L10n {
   }
 }
 
-export { L10n };
+const GenericL10n = null;
+
+export { GenericL10n, L10n };

web/pdf_page_view.js

@@ -43,7 +43,7 @@ import { AnnotationEditorLayerBuilder } from "./annotation_editor_layer_builder.
 import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
 import { compatibilityParams } from "./app_options.js";
 import { DrawLayerBuilder } from "./draw_layer_builder.js";
-import { NullL10n } from "web-l10n_utils";
+import { GenericL10n } from "web-null_l10n";
 import { SimpleLinkService } from "./pdf_link_service.js";
 import { StructTreeLayerBuilder } from "./struct_tree_layer_builder.js";
 import { TextAccessibilityManager } from "./text_accessibility.js";
@@ -157,7 +157,10 @@ class PDFPageView {
 
     this.eventBus = options.eventBus;
     this.renderingQueue = options.renderingQueue;
-    this.l10n = options.l10n || NullL10n;
+    this.l10n = options.l10n;
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
+      this.l10n ||= new GenericL10n();
+    }
 
     this.renderTask = null;
     this.resume = null;
@@ -214,7 +217,7 @@ class PDFPageView {
       }
 
       // Ensure that Fluent is connected in e.g. the COMPONENTS build.
-      if (this.l10n === NullL10n) {
+      if (!options.l10n) {
         this.l10n.translate(this.div);
       }
     }

web/pdf_viewer.component.js

@@ -30,7 +30,6 @@ import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
 import { DownloadManager } from "./download_manager.js";
 import { EventBus } from "./event_utils.js";
 import { GenericL10n } from "./genericl10n.js";
-import { NullL10n } from "./l10n_utils.js";
 import { PDFHistory } from "./pdf_history.js";
 import { PDFPageView } from "./pdf_page_view.js";
 import { PDFScriptingManager } from "./pdf_scripting_manager.component.js";
@@ -54,7 +53,6 @@ export {
   FindState,
   GenericL10n,
   LinkTarget,
-  NullL10n,
   parseQueryString,
   PDFFindController,
   PDFHistory,

web/pdf_viewer.js

@@ -63,7 +63,7 @@ import {
   VERTICAL_PADDING,
   watchScroll,
 } from "./ui_utils.js";
-import { NullL10n } from "web-l10n_utils";
+import { GenericL10n } from "web-null_l10n";
 import { PDFPageView } from "./pdf_page_view.js";
 import { PDFRenderingQueue } from "./pdf_rendering_queue.js";
 import { SimpleLinkService } from "./pdf_link_service.js";
@@ -286,7 +286,10 @@ class PDFViewer {
       this.removePageBorders = options.removePageBorders || false;
     }
     this.maxCanvasPixels = options.maxCanvasPixels;
-    this.l10n = options.l10n || NullL10n;
+    this.l10n = options.l10n;
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
+      this.l10n ||= new GenericL10n();
+    }
     this.#enablePermissions = options.enablePermissions || false;
     this.pageColors = options.pageColors || null;
 
@@ -327,7 +330,7 @@ class PDFViewer {
 
     if (
       (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) &&
-      this.l10n === NullL10n
+      !options.l10n
     ) {
       // Ensure that Fluent is connected in e.g. the COMPONENTS build.
       this.l10n.translate(this.container);