Next.js: Next.js from v9.3 to latest ignoring typescript errors

[mdaffan]

Bug report

Ignoring Typescript errors and getting compiled successfully with errors

Describe the bug

// Next.js API route support: https://nextjs.org/docs/api-routes/introduction

import { NextApiRequest, NextApiResponse } from 'next'

const handler = (req: NextApiRequest, res: NextApiResponse) => {
res.go = 200
res.json({ name: 'John Doe' })
}

export default handler
Vs code shows res.go as an error because it's an error but next.js v 9.4.4 is compiling it successfully 9.2 is fine and throwing errors in my project

[Timer]

Could you please share a full project? Including your tsconfig.json?

[mdaffan]

It's one of your examples itself actually while doing npx create-next-app I selected with-typescript and deliberately entered wrong Types for res as mentioned above and it compiled successfully while the same doesn't get compiled with create-react-app typescript template and also next 9.2 sometimes compile it successfully and sometimes shows typescript errors

[Timer]

TypeScript errors are not shown during development time (next dev) and during production build (next build).

[mdaffan]

It is getting shown for V 9.2 at least while running next dev

[Timer]

Yes, the behavior changed in 9.4 for the Fast Refresh experience!

[mdaffan]

I don't foresee why having compile-time errors while running dev isn't a good feature, Cause I personally find that feature in create-react-app really good