Swap JS minifier from uglify to terser

alphagov · Jan 16, 2023 · 04bd6d1 · 04bd6d1
1 parent 04a6669
commit 04bd6d1
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Showing 4 changed files with 22 additions and 52 deletions.
diff --git a/docs/examples/webpack/webpack.config.js b/docs/examples/webpack/webpack.config.js
@@ -67,8 +67,10 @@ module.exports = ({ WEBPACK_SERVE }, { mode }) => ({
     minimizer: [new TerserPlugin({
       extractComments: true,
       terserOptions: {
-        ecma: 5,
         format: { comments: false },
+
+        // Compatibility workarounds
+        ecma: 5,
         ie8: true,
         safari10: true
       }

diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -71,7 +71,7 @@
     "rollup": "0.59.4",
     "sassdoc": "^2.7.4",
     "slash": "^5.0.0",
-    "uglify-js": "^3.17.4",
+    "terser": "^5.16.1",
     "yargs-parser": "^21.1.1"
   },
   "devDependencies": {

diff --git a/tasks/compile-javascripts.mjs b/tasks/compile-javascripts.mjs
@@ -3,7 +3,7 @@ import { dirname, join, parse } from 'path'
 
 import PluginError from 'plugin-error'
 import { rollup } from 'rollup'
-import { minify } from 'uglify-js'
+import { minify } from 'terser'
 
 import { paths, pkg } from '../config/index.js'
 import { getListing } from '../lib/file-helper.js'
@@ -73,7 +73,7 @@ export async function compileJavaScript ([modulePath, { srcPath, destPath, minif
 
   // Minify bundle
   if (minify) {
-    result = minifyJavaScript(modulePath, result)
+    result = await minifyJavaScript(modulePath, result)
 
     // Create directories
     await mkdir(dirname(filePath), { recursive: true })
@@ -93,28 +93,24 @@ export async function compileJavaScript ([modulePath, { srcPath, destPath, minif
  * @param {object} result - Generated bundle
  * @param {string} result.code - Source code
  * @param {import('magic-string').SourceMap} result.map - Source map
- * @returns {import('uglify-js').MinifyOutput} Minifier result
+ * @returns {Promise<import('terser').MinifyOutput>} Minifier result
  */
 export function minifyJavaScript (modulePath, result) {
   const minified = minify({ [modulePath]: result.code }, {
+    format: { comments: false },
+
+    // Include source maps
     sourceMap: {
       content: result.map,
       filename: result.map.file,
       url: `${result.map.file}.map`,
       includeSources: true
     },
 
-    // Prevent unsafe polyfill changes
-    // https://github.com/mishoo/UglifyJS#compress-options
-    compress: {
-      inline: 2
-    },
-
     // Compatibility workarounds
+    ecma: 5,
     ie8: true,
-    module: false,
-    v8: true,
-    webkit: true
+    safari10: true
   })
 
   if (minified.error) {