ESLint - "no-unused-vars" on function parameters within TypeScript Types/Interfaces

Question

I am currently getting a eslint warning on function parameters within Types or Interfaces.

Doing the following:

type Test = {
  fn: (param: string) => void
}

Results in the following warning:

'param' is defined but never used. Allowed unused args must match /^_/u.

Here's what my .eslintrc.json looks like:

{
  "root": true,
  "parser": "@typescript-eslint/parser",
  "parserOptions": {
    "project": "tsconfig.json"
  },
  "env": {
    "node": true
  },
  "plugins": ["@typescript-eslint"],
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended",
    "plugin:prettier/recommended"
  ],
  "rules": {
    "@typescript-eslint/interface-name-prefix": "off",
    "@typescript-eslint/explicit-function-return-type": "off",
    "@typescript-eslint/explicit-module-boundary-types": "off"
  }
}

Package versions:

"eslint": "^7.23.0"
"@typescript-eslint/eslint-plugin": "^4.22.1"
"@typescript-eslint/parser": "^4.22.1"

Similar questions have been asked already here and here, but the provided answers do not seem to be doing it for me.

Any suggestions as to what could be happening?

I might be wrong, but probably restart your IDE. Specially, with VSCode, I have seen stale errors until I restart the IDE. It may not help, but may worth a try after you have done this https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unused-vars.md#how-to-use — Nishant, May 06 '21 at 03:10
Doing what's on the link just converts what I'm getting from a `warning` to an `error` — Hansel, May 06 '21 at 12:39

Elder Carvalho · Answer 1 · 2022-09-27T20:43:16.940

11

I've solved it this way, put these two lines in rules in the eslint configuration file.

"no-unused-vars": "off",
"@typescript-eslint/no-unused-vars": ["error"]

edited Sep 27 '22 at 20:43

answered Jul 24 '21 at 22:29

Elder Carvalho

688
4
14

for more info see: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unused-vars.md – gnupa Aug 20 '21 at 11:14

score 2 · Answer 2 · answered Mar 23 '22 at 15:34

Instead of setting the no-unused-vars globally in your eslint config, you could set it to the line by placing this comment just above it:

 // eslint-disable-next-line @typescript-eslint/no-unused-vars

or to the entire file, just add this comment on the top:

/* eslint-disable @typescript-eslint/no-unused-vars */

score 2 · Answer 3 · answered Nov 08 '22 at 06:21

You can configure the no-unused-vars rule to ignore arguments named param by adding this line to your .eslintrc.json rules: "no-unused-vars": ["error", { "argsIgnorePattern": "params"}]. See the docs: https://eslint.org/docs/latest/rules/no-unused-vars#argsignorepattern

ESLint - "no-unused-vars" on function parameters within TypeScript Types/Interfaces

3 Answers3