setupProxy.js not working together with TypeScript

Is this a bug report?

Yes

Environment

CRA ^2.0.6-next.c662dfb0 with TypeScript support

Steps to Reproduce

1. npx create-react-app --scripts-version @next myapp
2. cd myapp
3. yarn add typescript @types/react @types/react-dom @types/jest
4. mv src/index.{js,tsx}
5. Add src/setupProxy.js with following content:

const proxy = require('http-proxy-middleware')
    
module.exports = function(app) {
    app.use(proxy('/api', { target: 'http://localhost:5000/' }))
}

1. yarn run build

Expected Behavior

setupProxy.js should be compiled without any problems.

Actual Behavior

Behold the “Type error: Cannot compile namespaces when the ‘–isolatedModules’ flag is provided. TS1208” error message.

Additionally: if one were to rewrite the setupProxy.js script with proper ES6 exports like this:

const proxy = require('http-proxy-middleware')
    
export const setupProxy = (app) => {
    app.use(proxy('/api', { target: 'http://localhost:5000/' }))
}

yarn run build compiles successfully, while yarn run start claims “unexpected token export”.

[brunolemos]

Thanks for the report!

You are right. For now, please add this line to your tsconfig.json:

"exclude": ["src/setupProxy.js"]

Let me know if that fixes the issue for you.

[antonovicha]

@Timer it does not work in 2.1.1 for us. Workaround is working fine.