Format UglifyJs error (#2650)

* format UglifyJs error

* move formatBuildError to react-dev-utils

* fix readme

* use regex for plucking the path from stack

* make path human readable and fallback to show error if regex not matched

* rename to printBuildError and add link to the docs

* fix link indentation

* improve readibility + shorten link

Author: viankakrisna

packages/react-dev-utils/README.md

@@ -220,6 +220,20 @@ compiler.plugin('done', function(stats) {
 });
 ```
 
+#### `printBuildError(error: Object): void`
+
+Prettify some known build errors.
+Pass an Error object to log a prettified error message in the console.
+
+```
+  const printBuildError = require('react-dev-utils/printBuildError')
+  try {
+    build()
+  } catch(e) {
+    printBuildError(e) // logs prettified message
+  }
+```
+
 #### `getProcessForPort(port: number): string`
 
 Finds the currently running process on `port`.

packages/react-dev-utils/package.json

@@ -18,13 +18,14 @@
     "crossSpawn.js",
     "eslintFormatter.js",
     "FileSizeReporter.js",
+    "printBuildError.js",
     "formatWebpackMessages.js",
     "getProcessForPort.js",
     "inquirer.js",
     "InterpolateHtmlPlugin.js",
     "launchEditor.js",
-    "noopServiceWorkerMiddleware.js",
     "ModuleScopePlugin.js",
+    "noopServiceWorkerMiddleware.js",
     "openBrowser.js",
     "openChrome.applescript",
     "printHostingInstructions.js",

packages/react-dev-utils/printBuildError.js

@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+'use strict';
+
+const get = require('lodash/get');
+const chalk = require('chalk');
+
+module.exports = function printBuildError(err) {
+  const message = get(err, 'message');
+  const stack = get(err, 'stack');
+
+  // Add more helpful message for UglifyJs error
+  if (
+    stack &&
+    typeof message === 'string' &&
+    message.indexOf('from UglifyJs') !== -1
+  ) {
+    try {
+      const matched = /Unexpected token:(.+)\[(.+)\:(.+)\,(.+)\]\[.+\]/.exec(
+        stack
+      );
+      if (!matched) {
+        throw new Error(
+          "The regex pattern is not matched. Maybe UglifyJs changed it's message?"
+        );
+      }
+      const problemPath = matched[2];
+      const line = matched[3];
+      const column = matched[4];
+      console.log(
+        'Failed to minify the code from this file: \n\n',
+        chalk.yellow(`${problemPath} line ${line}:${column}`),
+        '\n'
+      );
+    } catch (ignored) {
+      console.log('Failed to minify the code.', err);
+    }
+    console.log('Read more here: http://bit.ly/2tRViJ9');
+  } else {
+    console.log((message || err) + '\n');
+  }
+  console.log();
+};

packages/react-scripts/scripts/build.js

@@ -34,6 +34,7 @@ const checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
 const formatWebpackMessages = require('react-dev-utils/formatWebpackMessages');
 const printHostingInstructions = require('react-dev-utils/printHostingInstructions');
 const FileSizeReporter = require('react-dev-utils/FileSizeReporter');
+const printBuildError = require('react-dev-utils/printBuildError');
 
 const measureFileSizesBeforeBuild =
   FileSizeReporter.measureFileSizesBeforeBuild;
@@ -104,7 +105,7 @@ measureFileSizesBeforeBuild(paths.appBuild)
     },
     err => {
       console.log(chalk.red('Failed to compile.\n'));
-      console.log((err.message || err) + '\n');
+      printBuildError(err);
       process.exit(1);
     }
   );

packages/react-scripts/template/README.md

@@ -92,6 +92,7 @@ You can find the most recent version of this guide [here](https://github.com/fac
   - [`npm test` hangs on macOS Sierra](#npm-test-hangs-on-macos-sierra)
   - [`npm run build` exits too early](#npm-run-build-exits-too-early)
   - [`npm run build` fails on Heroku](#npm-run-build-fails-on-heroku)
+  - [`npm run build` fails to minify](#npm-run-build-fails-to-minify)
   - [Moment.js locales are missing](#momentjs-locales-are-missing)
 - [Something Missing?](#something-missing)
 
@@ -2137,6 +2138,16 @@ moment.locale('fr');
 
 This will only work for locales that have been explicitly imported before.
 
+### `npm run build` fails to minify
+
+You may occasionally find a package you depend on needs compiled or ships code for a non-browser environment.<br>
+This is considered poor practice in the ecosystem and does not have an escape hatch in Create React App.<br>
+<br>
+To resolve this:
+1. Open an issue on the dependency's issue tracker and ask that the package be published pre-compiled (retaining ES6 Modules).
+2. Fork the package and publish a corrected version yourself.
+3. If the dependency is small enough, copy it to your `src/` folder and treat it as application code.
+
 ## Something Missing?
 
 If you have ideas for more “How To” recipes that should be on this page, [let us know](https://github.com/facebookincubator/create-react-app/issues) or [contribute some!](https://github.com/facebookincubator/create-react-app/edit/master/packages/react-scripts/template/README.md)