"noUnusedLocals" doesn't throw error on compiling with typescript

Question

I got no error during compilation with tsc option "noUnusedLocals" even if my linter find several of these errors. Is that the normal behaviour ? I use ts with next.js and webpack. Here's my tsconfig file :

{
  "compileOnSave": false,
  "compilerOptions": {
    "target": "es6",
    "module": "esnext",
    "checkJs": false,                         
    "sourceMap": true,
    "strict": true,
    "noImplicitAny":true,                   
    "strictFunctionTypes": true,                 
    "noUnusedLocals": true,                     
    "noUnusedParameters": true,                  
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "rootDir": "src",
    "outDir": "build",
    "lib": [
      "dom",
      "dom.iterable",
      "esnext",
      "es2017"
    ],
    "allowJs": true,
    "noEmit": false,
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "jsx": "preserve",
    "suppressImplicitAnyIndexErrors": false
  }
}

Thanks for your help.

Answer 1

That is not the expected behaviour. noUnusedLocals: true causes a tsc compilation error.

Confusingly, linters may ignore or warn on the error.

See the @microsoft/TypeScript closed issue Classify lintish diagnostics as warnings and open issues Add support for diagnostic severities and Feature Request: Linting should be a core feature of the language server for the unresolved discussion on this and similar "lintish" rules.