Webpack: add DeadCodePlugin to detect unused files

package.json

@@ -191,6 +191,7 @@
     "webpack-assets-manifest": "^5.0.6",
     "webpack-bundle-analyzer": "^4.4.2",
     "webpack-cli": "^4.8.0",
+    "webpack-deadcode-plugin": "^0.1.16",
     "webpack-merge": "^5.8.0",
     "wicg-inert": "^3.1.1"
   },

webpack/shared.js

@@ -9,6 +9,7 @@ const HtmlWebpackPlugin = require('html-webpack-plugin');
 const MiniCssExtractPlugin = require('mini-css-extract-plugin');
 const webpack = require('webpack');
 const AssetsManifestPlugin = require('webpack-assets-manifest');
+const DeadCodePlugin = require('webpack-deadcode-plugin');
 
 const { env, settings, output } = require('./configuration');
 const rules = require('./rules');
@@ -86,6 +87,19 @@ module.exports = {
       writeToDisk: true,
       publicPath: true,
     }),
+    // https://github.com/MQuy/webpack-deadcode-plugin
+    new DeadCodePlugin({
+      patterns: [
+        'app/**/*',
+      ],
+      exclude: [
+        '**/*.test.*',
+        '**/__*__/*',
+        '**/(LICENSE|README|COPYING)(.md|.txt)?',
+        // This file is imported with @preval
+        'app/soapbox/features/emoji/emoji_map.json',
+      ],
+    }),
     // https://github.com/jantimon/html-webpack-plugin#options
     new HtmlWebpackPlugin(makeHtmlConfig()),
     new HtmlWebpackPlugin(makeHtmlConfig({ filename: '404.html' })),

yarn.lock

@@ -10786,6 +10786,14 @@ webpack-cli@^4.8.0:
     v8-compile-cache "^2.2.0"
     webpack-merge "^5.7.3"
 
+webpack-deadcode-plugin@^0.1.16:
+  version "0.1.16"
+  resolved "https://registry.yarnpkg.com/webpack-deadcode-plugin/-/webpack-deadcode-plugin-0.1.16.tgz#f58ec7bd908325247396438a50afc209bfd01bdd"
+  integrity sha512-T3oRlzftN4jU8Wm8rjx9mzYC8zr4CND5kNgh6EBJyhWy68F5kZ334EjdBjOKDEpUHuybBuxi/SviVUFsP0gx4g==
+  dependencies:
+    chalk "^3.0.0"
+    fast-glob "^3.1.1"
+
 webpack-dev-middleware@^5.1.0:
   version "5.1.0"
   resolved "https://registry.yarnpkg.com/webpack-dev-middleware/-/webpack-dev-middleware-5.1.0.tgz#90a645b077e85f661c5bb967dc32adc3eceb5cfd"