Consistently set environment variables (facebook#2382)

packages/react-scripts/scripts/build.js

@@ -11,6 +11,7 @@
 'use strict';
 
 // Do this as the first thing so that any code reading it knows the right env.
+process.env.BABEL_ENV = 'production';
 process.env.NODE_ENV = 'production';
 
 // Makes the script crash on unhandled rejections instead of silently

packages/react-scripts/scripts/start.js

@@ -10,15 +10,17 @@
 // @remove-on-eject-end
 'use strict';
 
+// Do this as the first thing so that any code reading it knows the right env.
+process.env.BABEL_ENV = 'development';
+process.env.NODE_ENV = 'development';
+
 // Makes the script crash on unhandled rejections instead of silently
 // ignoring them. In the future, promise rejections that are not handled will
 // terminate the Node.js process with a non-zero exit code.
 process.on('unhandledRejection', err => {
   throw err;
 });
 
-process.env.NODE_ENV = 'development';
-
 // Ensure environment variables are read.
 require('../config/env');
 

packages/react-scripts/scripts/test.js

@@ -10,6 +10,8 @@
 // @remove-on-eject-end
 'use strict';
 
+// Do this as the first thing so that any code reading it knows the right env.
+process.env.BABEL_ENV = 'test';
 process.env.NODE_ENV = 'test';
 process.env.PUBLIC_URL = '';