add webpack-env-define-plugin package

packages/react-dev-utils/README.md

@@ -201,3 +201,33 @@ module.exports = {
   // ...
 }
 ```
+
+#### `envDefinePlugin({regex: string, customVariables: Object.<string, string>})`
+
+This function grabs environment variables that follows a specified regex and injects them into the application 
+using the webpack DefinePlugin.
+In addition, the function allows defining custom environment variables to be injected.
+
+To use first reference it in your webpack config:
+
+  ```js
+  var webpack = require('webpack');
+  var envDefinePlugin = require('react-dev-utils/webpackEnvDefinePlugin');
+  ```
+
+and define it as a plugin in the webpack config plugin section:
+
+ ```js
+  plugins: [
+     ...
+     new webpack.DefinePlugin(envDefinePlugin({
+       // Grab MY_PREFIX_* environment variables
+       regex: /^MY_PREFIX_/i,
+       customVariables: {
+         // Useful for injecting static values as environment variables to the application
+         'APP_NAME': 'My App'
+       }
+     })),
+     ...
+  ]
+ ```

packages/react-dev-utils/package.json

@@ -19,7 +19,8 @@
     "openBrowser.js",
     "prompt.js",
     "WatchMissingNodeModulesPlugin.js",
-    "webpackHotDevClient.js"
+    "webpackHotDevClient.js",
+    "webpackEnvDefinePlugin.js"
   ],
   "dependencies": {
     "ansi-html": "0.0.5",

packages/react-dev-utils/webpackEnvDefinePlugin.js

@@ -0,0 +1,47 @@
+/**
+ * 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';
+
+/**
+ * Generates a webpack define plugin config injecting environment variables that pass a regex test.
+ * The function also support custom variables by passing them in the options argument
+ *
+ * @param {Object} options - The plugin configuration
+ * @param {string} options.regex - The regex to select the environment variables by
+ * @param {Object.<string, string>} options.customVariables - A map that its keys are the
+ * custom injected environment
+ * variable names and its values are the variable values
+ * @returns - Returns a webpack define plugin configuration
+ */
+function envDefinePlugin(options) {
+  const regex = options.regex || /.*/;
+  const customVariables = options.customVariables || {};
+
+  return getClientEnvironment(regex, customVariables);
+}
+
+/**
+ * Grabs environment variables that meets the regex test and prepare them to be injected into the
+ * application via DefinePlugin in Webpack configuration.
+ * @param {string} regex - The regex to select the environment variables by
+ * @param {Object.<string, string>} customVariables - A map where its keys are the custom injected environment
+ * @returns {{[process.env]: *}} - A DefinePlugin configuration
+ */
+function getClientEnvironment(regex, customVariables) {
+  const processEnv = Object
+    .keys(process.env)
+    .filter(key => regex.test(key))
+    .reduce((env, key) => {
+      env[key] = JSON.stringify(process.env[key]);
+      return env;
+    }, customVariables);
+  return { 'process.env': processEnv };
+}
+
+module.exports = envDefinePlugin;

packages/react-scripts/config/webpack.config.dev.js

@@ -16,7 +16,7 @@ var HtmlWebpackPlugin = require('html-webpack-plugin');
 var CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
 var InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
 var WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
-var getClientEnvironment = require('./env');
+var envDefinePlugin = require('react-dev-utils/webpackEnvDefinePlugin');
 var paths = require('./paths');
 
 // Webpack uses `publicPath` to determine where the app is being served from.
@@ -26,8 +26,6 @@ var publicPath = '/';
 // as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
 // Omit trailing slash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
 var publicUrl = '';
-// Get environment variables to inject into our app.
-var env = getClientEnvironment(publicUrl);
 
 // This is the development configuration.
 // It is focused on developer experience and fast rebuilds.
@@ -195,9 +193,20 @@ module.exports = {
       inject: true,
       template: paths.appHtml,
     }),
-    // Makes some environment variables available to the JS code, for example:
-    // if (process.env.NODE_ENV === 'development') { ... }. See `./env.js`.
-    new webpack.DefinePlugin(env),
+    // Makes some environment variables available to the JS code
+    new webpack.DefinePlugin(envDefinePlugin({
+      // Grab REACT_APP_* environment variables
+      regex: /^REACT_APP_/i,
+      customVariables: {
+        // Set NODE_ENV to development
+        'NODE_ENV': JSON.stringify('development'),
+        // Useful for resolving the correct path to static assets in `public`.
+        // For example, <img src={process.env.PUBLIC_URL + '/img/logo.png'} />.
+        // This should only be used as an escape hatch. Normally you would put
+        // images into the `src` and `import` them in code to get their paths.
+        'PUBLIC_URL': JSON.stringify(publicUrl)
+      }
+    })),
     // This is necessary to emit hot updates (currently CSS only):
     new webpack.HotModuleReplacementPlugin(),
     // Watcher doesn't work well if you mistype casing in a path so we use

packages/react-scripts/config/webpack.config.prod.js

@@ -18,7 +18,7 @@ var ManifestPlugin = require('webpack-manifest-plugin');
 var InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
 var url = require('url');
 var paths = require('./paths');
-var getClientEnvironment = require('./env');
+var envDefinePlugin = require('react-dev-utils/webpackEnvDefinePlugin');
 
 function ensureSlash(path, needsSlash) {
   var hasSlash = path.endsWith('/');
@@ -45,14 +45,6 @@ var publicPath = ensureSlash(homepagePathname, true);
 // as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
 // Omit trailing slash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
 var publicUrl = ensureSlash(homepagePathname, false);
-// Get environment variables to inject into our app.
-var env = getClientEnvironment(publicUrl);
-
-// Assert this just to be safe.
-// Development builds of React are slow and not intended for production.
-if (env['process.env'].NODE_ENV !== '"production"') {
-  throw new Error('Production builds must have NODE_ENV=production.');
-}
 
 // This is the production configuration.
 // It compiles slowly and is focused on producing a fast and minimal bundle.
@@ -227,11 +219,21 @@ module.exports = {
         minifyURLs: true
       }
     }),
-    // Makes some environment variables available to the JS code, for example:
-    // if (process.env.NODE_ENV === 'production') { ... }. See `./env.js`.
-    // It is absolutely essential that NODE_ENV was set to production here.
-    // Otherwise React will be compiled in the very slow development mode.
-    new webpack.DefinePlugin(env),
+    // Makes some environment variables available to the JS code
+    new webpack.DefinePlugin(envDefinePlugin({
+      // Grab REACT_APP_* environment variables
+      regex: /^REACT_APP_/i,
+      customVariables: {
+        // It is absolutely essential that NODE_ENV is set to production here.
+        // Otherwise React will be compiled in the very slow development mode.
+        'NODE_ENV': JSON.stringify('production'),
+        // Useful for resolving the correct path to static assets in `public`.
+        // For example, <img src={process.env.PUBLIC_URL + '/img/logo.png'} />.
+        // This should only be used as an escape hatch. Normally you would put
+        // images into the `src` and `import` them in code to get their paths.
+        'PUBLIC_URL': JSON.stringify(publicUrl)
+      }
+    })),
     // This helps ensure the builds are consistent if source hasn't changed:
     new webpack.optimize.OccurrenceOrderPlugin(),
     // Try to dedupe duplicated modules, if any: