From b4ae958ca402d2b200250d3179ddcddad64adbd4 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 12 Jun 2020 15:08:51 +0200
Subject: [PATCH] Add basic support for the nullish coalescing operator `??`

For now we need to use a Babel-plugin, since Webpack 4.x doesn't seem to support it yet. (Most likely we'll have to update to Webpack 5, once that becomes available, in order for this to be directly supported. This is thus also blocked on removing the `webpack-stream` package.)

While the `??` operator will thus always be transpiled by Babel, even in modern builds, simply supporting it for development purposes seems like a step in the right direction.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator
---
 gulpfile.js               | 6 ++++++
 package.json              | 1 +
 web/pdf_thumbnail_view.js | 4 ++--
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gulpfile.js b/gulpfile.js
index 120d4fdba..a850f717d 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -215,6 +215,12 @@ function createWebpackConfig(defines, output) {
           options: {
             presets: skipBabel ? undefined : ["@babel/preset-env"],
             plugins: [
+              [
+                "@babel/plugin-proposal-nullish-coalescing-operator",
+                {
+                  loose: true,
+                },
+              ],
               "@babel/plugin-transform-modules-commonjs",
               [
                 "@babel/plugin-transform-runtime",
diff --git a/package.json b/package.json
index c4cc931b1..6de76c459 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "2.0.0",
   "devDependencies": {
     "@babel/core": "^7.10.1",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.10.1",
     "@babel/plugin-transform-modules-commonjs": "^7.10.1",
     "@babel/plugin-transform-runtime": "^7.10.1",
     "@babel/preset-env": "^7.10.1",
diff --git a/web/pdf_thumbnail_view.js b/web/pdf_thumbnail_view.js
index 81b7c36d4..d18e9ca3f 100644
--- a/web/pdf_thumbnail_view.js
+++ b/web/pdf_thumbnail_view.js
@@ -448,7 +448,7 @@ class PDFThumbnailView {
   get _thumbPageTitle() {
     return this.l10n.get(
       "thumb_page_title",
-      { page: this.pageLabel !== null ? this.pageLabel : this.id },
+      { page: this.pageLabel ?? this.id },
       "Page {{page}}"
     );
   }
@@ -456,7 +456,7 @@ class PDFThumbnailView {
   get _thumbPageCanvas() {
     return this.l10n.get(
       "thumb_page_canvas",
-      { page: this.pageLabel !== null ? this.pageLabel : this.id },
+      { page: this.pageLabel ?? this.id },
       "Thumbnail of Page {{page}}"
     );
   }