Make scripts crash on unhandled rejections (facebook#1819)

* Makes end-to-end testing crash on unhandled rejections

* Comment fix

scripts/build.js

@@ -13,6 +13,13 @@
 // Do this as the first thing so that any code reading it knows the right env.
 process.env.NODE_ENV = 'production';
 
+// 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;
+});
+
 // Load environment variables from .env file. Suppress warnings using silent
 // if this file is missing. dotenv will never modify any environment variables
 // that have already been set.

scripts/eject.js

@@ -9,6 +9,13 @@
  */
 'use strict';
 
+// 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;
+});
+
 const fs = require('fs-extra');
 const path = require('path');
 const spawnSync = require('cross-spawn').sync;

scripts/init.js

@@ -9,6 +9,13 @@
  */
 'use strict';
 
+// 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;
+});
+
 const fs = require('fs-extra');
 const path = require('path');
 const spawn = require('cross-spawn');

scripts/start.js

@@ -10,6 +10,13 @@
 // @remove-on-eject-end
 'use strict';
 
+// 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';
 
 // Load environment variables from .env file. Suppress warnings using silent

scripts/test.js

@@ -13,6 +13,13 @@
 process.env.NODE_ENV = 'test';
 process.env.PUBLIC_URL = '';
 
+// 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;
+});
+
 // Load environment variables from .env file. Suppress warnings using silent
 // if this file is missing. dotenv will never modify any environment variables
 // that have already been set.