How can I stop Next.js from messing with my tsconfig?

[wereHamster]

Summary

Whenever I start next dev server, it overwrites my tsconfig with its opinionated settings:

   We detected TypeScript in your project and reconfigured your tsconfig.json file for you. Strict-mode is set to false by default.
   The following suggested values were added to your tsconfig.json. These values can be changed to fit your project's needs:

   	- strictNullChecks was set to true

How can I stop Next.js from doing that?

Additional information

No response

Example

No response

[boydenhartog]

I'm also running into this issue with version: 13.5.6

[arimgibson]

I didn't have the issue with the strictNullChecks property but another value (noEmit) that said "These values can be changed" in the error message. It would default to adding it to true, and add it back in every time I deleted it. Instead, I kept the value there but set to false and the error stopped. Might help here!

[ssalbdivad]

This is genuinely terrible behavior if you don't want to allow certain settings just give a warning.

node is an outdated moduleResolution setting that doesn't respect package.json exports (added in Node 12 which is long since deprecated).

Why overwrite whatever I try to add with that? I've never seen a dev tool be that overly aggressive about screwing up my configs.

[adamshaylor]

I stumbled into this when I was importing some uncompiled React components from another library. I tried using the Bundler value. Rewriting my tsconfig.json was an unpleasant surprise. In some cases, it will even generate invalid combinations:

The flow of a build process should be unidirectional. A build tool that modifies source (and tsconfig.json is definitely source) is creating more problems than it solves.

[LuxXx]

I am using extends, that points to another tsconfig from another package (which also extends from a base tsconfig) using turborepo.
The base tsconfig is really strict, but

tsconfig.json:

{
  "extends": "@repo/typescript-config/nextjs.json",
  "compilerOptions": {
    "paths": {
      "@/*": ["./src/*"]
    },
  },
  "include": [
    "next-env.d.ts",
    "next.config.js",
    "**/*.ts",
    "**/*.tsx",
    ".next/types/**/*.ts"
  ],
  "exclude": ["node_modules"]
}

nextjs.json:

{
  "$schema": "https://json.schemastore.org/tsconfig",
  "display": "Next.js",
  "extends": "./base.json",
  "compilerOptions": {
    "plugins": [{ "name": "next" }],
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "allowJs": true,
    "jsx": "preserve",
    "noEmit": true
  }
}

base.json:

{
  "$schema": "https://json.schemastore.org/tsconfig",
  "display": "Default",
  "compilerOptions": {
    "declaration": false,
    "declarationMap": false,
    "esModuleInterop": true,
    "incremental": true,
    "isolatedModules": true,
    "lib": ["es2022", "DOM", "DOM.Iterable"],
    "module": "NodeNext",
    "moduleDetection": "force",
    "moduleResolution": "NodeNext",
    "noUncheckedIndexedAccess": true,
    "resolveJsonModule": true,
    "skipLibCheck": true,
    "strict": true,
    "target": "ES2022",
    "forceConsistentCasingInFileNames": true
  }
}

Starting the dev server immediately overwrites my tsconfig even though it should be strict already.

We detected TypeScript in your project and reconfigured your tsconfig.json file for you. Strict-mode is set to false by default.
             │   The following suggested values were added to your tsconfig.json. These values can be changed to fit your project's needs:
             │
             │        - strictNullChecks was set to true

[ozdv]

Did you end up resolving this @LuxXx ? I am encountering this now setting up tailwind with nextjs and turborepo as well, and nextjs overwriting it on build is causing issues

[vinnymac]

Here is how I worked around the issue above: https://gist.github.com/vinnymac/efa90137f8c7026490c4b19f8ab73286

In case it helps you.

[hbystrom91]

i have the same issue. why the heck is next messing with my tsconfig? due to legacy reasons, i don't want strictNullChecks to be set to true. this basically breaks my app.

[GoodbyeNJN]

I also struggled with this issue, and I don't think the vercel team will take the advice to leave tsconfig unchanged. So I wrote a little script dedicated to patch next.js, just simply run npx stop-nextjs-from-messing-tsconfig from the project folder, feel free to try it out.

Source code: https://www.npmjs.com/package/stop-nextjs-from-messing-tsconfig

[apetta]

The pursuit of optimal DX is a double edged sword - this ones hurts more than it helps!