package/env.js in webpacker-6.0.0.pre.2 vs package/env.js in webpacker-6.0.0.rc.1

@@ -14,11 +14,17 @@
 
 const config = safeLoad(readFileSync(configPath), 'utf8')
 const availableEnvironments = Object.keys(config).join('|')
 const regex = new RegExp(`^(${availableEnvironments})$`, 'g')
 
+// v4 of webpack-dev-server will switch to WEBPACK_DEV_SERVE
+// https://github.com/rails/webpacker/issues/3057
+const runningWebpackDevServer = process.env.WEBPACK_DEV_SERVER === 'true' ||
+  process.env.WEBPACK_DEV_SERVE === 'true'
+
 module.exports = {
   railsEnv: railsEnv && railsEnv.match(regex) ? railsEnv : DEFAULT,
   nodeEnv,
   isProduction,
-  isDevelopment
+  isDevelopment,
+  runningWebpackDevServer
 }