build: improve tree-shaking (#7325)

* build: improve tree-shaking

* dedup terser

craco.config.cjs

@@ -5,7 +5,6 @@ const { execSync } = require('child_process')
 const MiniCssExtractPlugin = require('mini-css-extract-plugin')
 const path = require('path')
 const ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin')
-const TerserPlugin = require('terser-webpack-plugin')
 const { IgnorePlugin, ProvidePlugin } = require('webpack')
 const { RetryChunkLoadPlugin } = require('webpack-retry-chunk-load-plugin')
 
@@ -146,18 +145,20 @@ module.exports = {
         return rule
       })
 
+      // Run terser compression on node_modules before tree-shaking, so that tree-shaking is more effective.
+      // This works by eliminating dead code, so that webpack can identify unused imports and tree-shake them;
+      // it is only necessary for node_modules - it is done through linting for our own source code -
+      // see https://medium.com/engineering-housing/dead-code-elimination-and-tree-shaking-at-housing-part-1-307a94b30f23#7e03:
+      webpackConfig.module.rules.push({
+        enforce: 'post',
+        test: /node_modules.*\.(js)$/,
+        loader: path.join(__dirname, 'scripts/terser-loader.js'),
+        options: { compress: true, mangle: false },
+      })
+
       // Configure webpack optimization:
       webpackConfig.optimization = Object.assign(
         webpackConfig.optimization,
-        {
-          minimize: isProduction,
-          minimizer: [
-            new TerserPlugin({
-              minify: TerserPlugin.swcMinify,
-              parallel: require('os').cpus().length,
-            }),
-          ],
-        },
         isProduction
           ? {
               splitChunks: {

package.json

@@ -152,6 +152,7 @@
     "source-map-explorer": "^2.5.3",
     "start-server-and-test": "^2.0.0",
     "swc-loader": "^0.2.3",
+    "terser": "^5.19.4",
     "terser-webpack-plugin": "^5.3.9",
     "ts-jest": "^29.1.1",
     "ts-transform-graphql-tag": "^0.2.1",

scripts/terser-loader.js

@@ -0,0 +1,15 @@
+/* eslint-env node */
+
+const { minify } = require('terser')
+
+module.exports = async function terserLoader(source, map, meta) {
+  const callback = this.async()
+  const options = this.getOptions()
+  try {
+    const data = await minify(source, options)
+    const { code } = data || {}
+    callback(null, code, map, meta)
+  } catch (e) {
+    callback(e)
+  }
+}

yarn.lock

@@ -19494,10 +19494,10 @@ terser-webpack-plugin@^5.2.5, terser-webpack-plugin@^5.3.7, terser-webpack-plugi
     serialize-javascript "^6.0.1"
     terser "^5.16.8"
 
-terser@^5.0.0, terser@^5.10.0, terser@^5.16.8:
+terser@^5.0.0, terser@^5.10.0, terser@^5.16.8, terser@^5.19.4:
-  version "5.19.2"
+  version "5.19.4"
-  resolved "https://registry.yarnpkg.com/terser/-/terser-5.19.2.tgz#bdb8017a9a4a8de4663a7983f45c506534f9234e"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-5.19.4.tgz#941426fa482bf9b40a0308ab2b3cd0cf7c775ebd"
-  integrity sha512-qC5+dmecKJA4cpYxRa5aVkKehYsQKc+AHeKl0Oe62aYjBL8ZA33tTljktDHJSaxxMnbI5ZYw+o/S2DxxLu8OfA==
+  integrity sha512-6p1DjHeuluwxDXcuT9VR8p64klWJKo1ILiy19s6C9+0Bh2+NWTX6nD9EPppiER4ICkHDVB1RkVpin/YW2nQn/g==
   dependencies:
     "@jridgewell/source-map" "^0.3.3"
     acorn "^8.8.2"