Option 'noEmit' cannot be specified with option 'incremental'

Question

I am developing a next.js app. It has the following tsconfig.js

{
  "compilerOptions": {
    "target": "ES2018",
    "module": "esnext",
    "lib": [
      "dom",
      "es2018",
      "es2019.array"
    ],
    "jsx": "preserve",
    "sourceMap": true,
    "skipLibCheck": true,
    "strict": true,
    "esModuleInterop": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "allowJs": true,
    "forceConsistentCasingInFileNames": true,
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,
    "incremental": true
  },
  "exclude": [
    "server",
    "next.config.js"
  ],
  "include": [
    "lib/global.d.ts",
    "next-env.d.ts",
    "**/*.ts",
    "**/*.tsx",
    "**/*.js"
  ]
}

It is running well in the development mode but while creating build it shows following error:

ERROR in tsconfig.json
22:5 Option 'noEmit' cannot be specified with option 'incremental'.
    20 |     "resolveJsonModule": true,
    21 |     "isolatedModules": true,
  > 22 |     "noEmit": true,
       |     ^
    23 |     "incremental": true
    24 |   },
    25 |   "exclude": [

Next.js automatically injects 'noEmit: true' in tsconfig.json file. While i really need the incremental mode for faster builds. What can be the solution to this?

Answer 1

TS 4.0+

--incremental with --noEmit is possible now:

"compilerOptions": {
  "noEmit": true,
  "incremental": true,
  // "tsBuildInfoFile": "/tmp/my-proj/tsbuildinfo" // custom build info file path
  // ...
}

The build info file is emitted even with noEmit. You can set its explicit location via --tsBuildInfoFile. Otherwise outDir - if still set - or tsconfig.json project root is taken as emit directory.

Older versions (workaround)

  "compilerOptions": {
    "incremental": true,
    "declaration": true,
    "emitDeclarationOnly": true, // to emit at least something
    // "noEmit": true,
    // ...
    
    // Either set overall output directory
    "outDir": "dist",
    //  or separate locations for build file and declarations 
    // "declarationDir": "dist"
    // "tsBuildInfoFile": "/tmp/my-proj/tsbuildinfo"
  }

More info

• Allow noEmit and composite together in 3.7 #33809
• .tsbuildinfo file should be created when the noEmit flag is enabled #30661

Answer 2

From TypeScript issue #33809:

It really doesn't make sense to have incremental and noEmit together, since noEmit prevents us from writing incremental metadata. (So nothing is actually incremental).

You should consider emitDeclarationOnly instead of noEmit, if you actually just want incremental checking.

According to this, the incremental: true flag has done nothing to speed up the build while noEmit: true is defined. So you should either remove noEmit: true or change it to emitDeclarationOnly: true.

You can control the output folders using outDir and declarationDir.