Don't run yarn after ejecting (facebook#2634)

Author: gaearon

packages/react-scripts/scripts/eject.js

@@ -220,8 +220,21 @@ inquirer
  }
 
  if (fs.existsSync(paths.yarnLockFile)) {
- console.log(cyan('Running yarn...'));
- spawnSync('yarnpkg', [], { stdio: 'inherit' });
+ // TODO: this is disabled for three reasons.
+ //
+ // 1. It produces garbage warnings on Windows on some systems:
+ // https://github.com/facebookincubator/create-react-app/issues/2030
+ //
+ // 2. For the above reason, it breaks Windows CI:
+ // https://github.com/facebookincubator/create-react-app/issues/2624
+ //
+ // 3. It is wrong anyway: re-running yarn will respect the lockfile
+ // rather than package.json we just updated. Instead we should have
+ // updated the lockfile. So we might as well not do it while it's broken.
+ // https://github.com/facebookincubator/create-react-app/issues/2627
+ //
+ // console.log(cyan('Running yarn...'));
+ // spawnSync('yarnpkg', [], { stdio: 'inherit' });
  } else {
  console.log(cyan('Running npm install...'));
  spawnSync('npm', ['install'], { stdio: 'inherit' });