TypeScript linter warning: no-unused-variable is d

Question

Today I see this warning in a project being refreshed after 3 months.

no-unused-variable is deprecated. Since TypeScript 2.9. Please use the built-in compiler checks instead.

But my tsconfig.json does not seem to use this.

{
  "compilerOptions": {
    "lib": ["es6"],
    "module": "commonjs",
    "noImplicitReturns": true,
    "outDir": "lib",
    "sourceMap": true,
    "target": "es6",
    "allowJs" : true
  },
  "compileOnSave": true,
  "include": [
    "src"
  ]
}

Probably it's a config implicit in any of the previous configs.

Could you point me to what to do to fix it?

If usefull

$ node -v
v10.3.0
$ npm -v
6.1.0

And these are devDependencies relates to type script in my package.json

"devDependencies": {
    ...
    "tslint": "^5.11.0",
    "typescript": "^2.9.1"
    ...
  },

Answer 1

As it says, tslint deprecated that rule (more info here https://github.com/palantir/tslint/pull/3919)

Check your tslint.json, and remove the rule and the warning should disappear.

Answer 2

Not only support for no-unused-variable rule, but the whole TSLint has been deprecated in favor of typescript-eslint.

Consider migration to new linter.

Answer 3

no-unused-variable is deprecated. Since TypeScript 2.9. Please use the built-in compiler checks instead.

1. Remove deprecated no-unused-variable from your or dependency tslint.json file.

2. Specify the following compiler options in your tsconfig.json file.

"compilerOptions": {
  "noUnusedLocals": true,                /* Report errors on unused locals. */
  "noUnusedParameters": true             /* Report errors on unused parameters. */
}