feat(disable-chunks): assert minimum required version

Author: Nargonath

scripts/index.js

@@ -6,6 +6,7 @@ const importCwd = require('import-cwd');
 const fs = require('fs-extra');
 const path = require('path');
 const ora = require('ora');
+const assert = require('assert');
 
 const {
   flags: { buildPath, publicPath, reactScriptsVersion, verbose, disableChunks },
@@ -23,8 +24,8 @@ const config =
         ? importCwd('./config/webpack.config')
         : importCwd('react-scripts/config/webpack.config'))('development')
     : isEjected
-      ? importCwd('./config/webpack.config.dev')
-      : importCwd('react-scripts/config/webpack.config.dev');
+    ? importCwd('./config/webpack.config.dev')
+    : importCwd('react-scripts/config/webpack.config.dev');
 
 const HtmlWebpackPlugin = importCwd('html-webpack-plugin');
 const InterpolateHtmlPlugin = importCwd('react-dev-utils/InterpolateHtmlPlugin');
@@ -60,6 +61,7 @@ config.output.filename = `js/bundle.js`;
 config.output.chunkFilename = `js/[name].chunk.js`;
 
 if (disableChunks) {
+  assert(major >= 2, 'Split chunks optimization is only available in react-scripts >= 2.0.0');
   // disable code-splitting/chunks
   config.optimization.runtimeChunk = false;
 
@@ -106,8 +108,7 @@ spinner.start('Clear destination folder');
 
 let inProgress = false;
 
-fs
-  .emptyDir(paths.appBuild)
+fs.emptyDir(paths.appBuild)
   .then(() => {
     spinner.succeed();