Don't mangle i18n

.github/workflows/nodejs.yml

@@ -33,3 +33,33 @@ jobs:
         run: yarn install
       - name: typecheck
         run: yarn flow
+  test:
+    runs-on: ubuntu-latest
+    env:
+      CI: true
+    steps:
+      - uses: actions/checkout@v1
+      - name: Use Node.js 12.x
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12.x
+      - name: Get yarn cache
+        id: yarn-cache
+        run: echo "::set-output name=dir::$(yarn cache dir)"
+      - uses: actions/cache@v1
+        with:
+          path: ${{ steps.yarn-cache.outputs.dir }}
+          key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-yarn-
+      - name: Cache node modules
+        uses: actions/cache@v1
+        with:
+          path: node_modules
+          key: ${{ runner.OS }}-build-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.OS }}-node_modules-
+      - name: yarn install
+        run: yarn install
+      - name: jest tests
+        run: yarn test

package.json

@@ -76,6 +76,7 @@
     "react-dom": "16.5",
     "react-router-dom": "^4.2.2",
     "react-transition-group": "^4.4.1",
+    "terser-webpack-plugin": "^4.2.3",
     "webpack": "^4.32.2",
     "webpack-cli": "^3.3.2",
     "webpack-dev-server": "^3.4.1"

terser.js

@@ -0,0 +1,49 @@
+/**
+ * Configuration for Terser optimisation that's shared.
+ *
+ * To use, import as `terserOptions` and spread into the `optimize` section
+ * in the webpack config.
+ */
+const TerserPlugin = require("terser-webpack-plugin");
+
+const PRESERVED_IDENTIFIERS = [
+    "i18n",
+];
+
+module.exports = {
+    minimize: true,
+    minimizer: [
+        new TerserPlugin({
+            // Enable caching to reduce time of subseqeuent builds
+            cache: true,
+            // Don't touch .css or .less files or any of the files
+            // that we explicitly want to avoid compressing.
+            // NOTE(jeresig): Changing this list may result in bundles
+            // not being updated properly until their underlying
+            // contents change (disabling minimization doesn't change
+            // the hash). See: WEB-629.
+            exclude: [/\.(css|less)$/],
+            // Use ALL the cores (seriously)
+            parallel: true,
+            // Make it possible to generate source maps
+            sourceMap: true,
+            // Don't extract the comments/licenses
+            extractComments: false,
+            // Additional options passed to terser itself
+            terserOptions: {
+                // Make it use a modern ECMAScript release
+                // NOTE(jeresig): If/when we change this there should be a
+                // full QE pass to confirm that our supported browsers still
+                // work as expected.
+                ecma: 2018,
+                // We want to compress as it reduces the gzipped filesize by
+                // about 5%, which is not trivial!
+                compress: true,
+                mangle: {
+                    // Retain some identifiers (see above)
+                    reserved: PRESERVED_IDENTIFIERS,
+                },
+            },
+        }),
+    ],
+};

webpack.config.externals.js

@@ -2,6 +2,8 @@ const path = require("path");
 const webpack = require("webpack");
 const MiniCssExtractPlugin = require("mini-css-extract-plugin");
 
+const terserOptions = require("./terser.js");
+
 module.exports = {
     entry: "./src/index.js",
     mode: "production",
@@ -12,7 +14,7 @@ module.exports = {
         libraryTarget: "umd",
     },
     optimization: {
-        minimize: true,
+        ...terserOptions,
     },
     module: {
         rules: [