Fix CI on Windows by writing .cmd file back

Author: gaearon

packages/react-scripts/scripts/eject.js

@@ -237,8 +237,35 @@ inquirer
     }
 
     if (fs.existsSync(paths.yarnLockFile)) {
+      const windowsCmdFilePath = path.join(
+        appPath,
+        'node_modules',
+        '.bin',
+        'react-scripts.cmd'
+      );
+      let windowsCmdFileContent;
+      if (process.platform === 'win32') {
+        // https://github.com/facebookincubator/create-react-app/pull/3806#issuecomment-357781035
+        // Yarn is diligent about cleaning up after itself, but this causes the react-scripts.cmd file
+        // to be deleted while it is running. This trips Windows up after the eject completes.
+        // We'll read the batch file and later "write it back" to match npm behavior.
+        try {
+          windowsCmdFileContent = fs.readFileSync(windowsCmdFilePath);
+        } catch (err) {
+          // If this fails we're not worse off than if we didn't try to fix it.
+        }
+      }
+
       console.log(cyan('Running yarn...'));
       spawnSync('yarnpkg', ['--cwd', process.cwd()], { stdio: 'inherit' });
+
+      if (windowsCmdFileContent && !fs.existsSync(windowsCmdFilePath)) {
+        try {
+          fs.writeFileSync(windowsCmdFilePath, windowsCmdFileContent);
+        } catch (err) {
+          // If this fails we're not worse off than if we didn't try to fix it.
+        }
+      }
     } else {
       console.log(cyan('Running npm install...'));
       spawnSync('npm', ['install', '--loglevel', 'error'], {