add --offline flag when we are using yarn and we are offline

packages/create-react-app/index.js

@@ -58,6 +58,7 @@ var path = require('path');
 var execSync = require('child_process').execSync;
 var spawn = require('cross-spawn');
 var semver = require('semver');
+var dns = require('dns');
 
 var projectName;
 
@@ -145,25 +146,37 @@ function shouldUseYarn() {
   }
 }
 
-function install(dependencies, verbose, callback) {
-  var command;
-  var args;
-  if (shouldUseYarn()) {
-    command = 'yarnpkg';
-    args = [ 'add', '--exact'].concat(dependencies);
-  } else {
-    checkNpmVersion();
-    command = 'npm';
-    args = ['install', '--save', '--save-exact'].concat(dependencies);
-  }
+function install(dependencies, verbose, isOnline) {
+  return new Promise(function(resolve, reject) {
+    var command;
+    var args;
+    if (shouldUseYarn()) {
+      command = 'yarnpkg';
+      args = [
+        'add',
+        '--exact',
+        isOnline === false && '--offline'
+      ].concat(dependencies);
+    } else {
+      checkNpmVersion();
+      command = 'npm';
+      args = ['install', '--save', '--save-exact'].concat(dependencies);
+    }
 
-  if (verbose) {
-    args.push('--verbose');
-  }
+    if (verbose) {
+      args.push('--verbose');
+    }
+
+    var child = spawn(command, args, {stdio: 'inherit'});
+    child.on('close', function(code) {
+      if (code !== 0) {
+        console.log();
+        console.error('Aborting installation.', chalk.cyan(command + ' ' + args.join(' ')), 'has failed.');
+        reject();
+      }
 
-  var child = spawn(command, args, {stdio: 'inherit'});
-  child.on('close', function(code) {
-    callback(code, command, args);
+      resolve(isOnline);
+    });
   });
 }
 
@@ -180,35 +193,11 @@ function run(root, appName, version, verbose, originalDirectory, template) {
   );
   console.log();
 
-  install(allDependencies, verbose, function(code, command, args) {
-    if (code !== 0) {
-      console.log();
-      console.error('Aborting installation.', chalk.cyan(command + ' ' + args.join(' ')), 'has failed.');
-      // On 'exit' we will delete these files from target directory.
-      var knownGeneratedFiles = [
-        'package.json', 'npm-debug.log', 'yarn-error.log', 'yarn-debug.log', 'node_modules'
-      ];
-      var currentFiles = fs.readdirSync(path.join(root));
-      currentFiles.forEach(function (file) {
-        knownGeneratedFiles.forEach(function (fileToMatch) {
-          // This will catch `(npm-debug|yarn-error|yarn-debug).log*` files
-          // and the rest of knownGeneratedFiles.
-          if ((fileToMatch.match(/.log/g) && file.indexOf(fileToMatch) === 0) || file === fileToMatch) {
-            console.log('Deleting generated file...', chalk.cyan(file));
-            fs.removeSync(path.join(root, file));
-          }
-        });
-      });
-      var remainingFiles = fs.readdirSync(path.join(root));
-      if (!remainingFiles.length) {
-        // Delete target folder if empty
-        console.log('Deleting', chalk.cyan(appName + '/'), 'from', chalk.cyan(path.resolve(root, '..')));
-        fs.removeSync(path.join(root));
-      }
-      console.log('Done.');
-      process.exit(1);
-    }
-
+  checkIfOnline()
+  .then(function(isOnline) {
+    return install(allDependencies, verbose, isOnline);
+  })
+  .then(function(isOnline) {
     checkNodeVersion(packageName);
 
     // Since react-scripts has been installed with --save
@@ -223,7 +212,32 @@ function run(root, appName, version, verbose, originalDirectory, template) {
       'init.js'
     );
     var init = require(scriptsPath);
-    init(root, appName, verbose, originalDirectory, template);
+    init(root, appName, verbose, originalDirectory, template, isOnline);
+  })
+  .catch(function(command, args) {
+    // On 'exit' we will delete these files from target directory.
+    var knownGeneratedFiles = [
+      'package.json', 'npm-debug.log', 'yarn-error.log', 'yarn-debug.log', 'node_modules'
+    ];
+    var currentFiles = fs.readdirSync(path.join(root));
+    currentFiles.forEach(function (file) {
+      knownGeneratedFiles.forEach(function (fileToMatch) {
+        // This will catch `(npm-debug|yarn-error|yarn-debug).log*` files
+        // and the rest of knownGeneratedFiles.
+        if ((fileToMatch.match(/.log/g) && file.indexOf(fileToMatch) === 0) || file === fileToMatch) {
+          console.log('Deleting generated file...', chalk.cyan(file));
+          fs.removeSync(path.join(root, file));
+        }
+      });
+    });
+    var remainingFiles = fs.readdirSync(path.join(root));
+    if (!remainingFiles.length) {
+      // Delete target folder if empty
+      console.log('Deleting', chalk.cyan(appName + '/'), 'from', chalk.cyan(path.resolve(root, '..')));
+      fs.removeSync(path.join(root));
+    }
+    console.log('Done.');
+    process.exit(1);
   });
 }
 
@@ -364,3 +378,11 @@ function isSafeToCreateProjectIn(root) {
       return validFiles.indexOf(file) >= 0;
     });
 }
+
+function checkIfOnline() {
+  return new Promise(function(resolve) {
+    dns.resolve('registry.yarnpkg.com', function(err) {
+      resolve(err === null);
+    });
+  });
+}

packages/react-scripts/scripts/init.js

@@ -12,7 +12,7 @@ var path = require('path');
 var spawn = require('cross-spawn');
 var chalk = require('chalk');
 
-module.exports = function(appPath, appName, verbose, originalDirectory, template) {
+module.exports = function(appPath, appName, verbose, originalDirectory, template, isOnline) {
   var ownPackageName = require(path.join(__dirname, '..', 'package.json')).name;
   var ownPath = path.join(appPath, 'node_modules', ownPackageName);
   var appPackage = require(path.join(appPath, 'package.json'));
@@ -69,7 +69,10 @@ module.exports = function(appPath, appName, verbose, originalDirectory, template
 
   if (useYarn) {
     command = 'yarnpkg';
-    args = ['add'];
+    args = [
+      'add',
+      isOnline === false && '--offline'
+    ];
   } else {
     command = 'npm';
     args = [