Tell user what browser support their application was built with (face…

…book#3782)

* Warn about browsers during build

* Better message

config/paths.js

@@ -49,6 +49,7 @@ function getServedPath(appPackageJson) {
 // config after eject: we're in ./config/
 module.exports = {
   dotenv: resolveApp('.env'),
+  appPath: resolveApp('.'),
   appBuild: resolveApp('build'),
   appPublic: resolveApp('public'),
   appHtml: resolveApp('public/index.html'),

package.json

@@ -68,5 +68,9 @@
   },
   "optionalDependencies": {
     "fsevents": "1.1.2"
+  },
+  "browserslist": {
+    "development": "last 2 chrome versions",
+    "production": [">1%", "last 4 versions", "Firefox ESR", "not ie < 11"]
   }
 }

scripts/build.js

@@ -40,6 +40,14 @@ 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 { printBrowsers } = require('react-dev-utils/browsersHelper');
+// @remove-on-eject-begin
+// Require browsers to be specified before you eject
+const { checkBrowsers } = require('react-dev-utils/browsersHelper');
+if (!checkBrowsers(paths.appPath)) {
+  process.exit(1);
+}
+// @remove-on-eject-end
 
 const measureFileSizesBeforeBuild =
   FileSizeReporter.measureFileSizesBeforeBuild;
@@ -107,6 +115,7 @@ measureFileSizesBeforeBuild(paths.appBuild)
         buildFolder,
         useYarn
       );
+      printBrowsers(paths.appPath);
     },
     err => {
       console.log(chalk.red('Failed to compile.\n'));

scripts/start.js

@@ -48,6 +48,13 @@ const createDevServerConfig = require('../config/webpackDevServer.config');
 
 const useYarn = fs.existsSync(paths.yarnLockFile);
 const isInteractive = process.stdout.isTTY;
+// @remove-on-eject-begin
+// Require browsers to be specified before you eject
+const { checkBrowsers } = require('react-dev-utils/browsersHelper');
+if (!checkBrowsers(paths.appPath)) {
+  process.exit(1);
+}
+// @remove-on-eject-end
 
 // Warn and crash if required files are missing
 if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {