no-unused-variable is deprecated.

[ghost]

Bug Report

• TSLint version: 5.11.0
• TypeScript version: 2.9.2
• Running TSLint via: Node.js

TypeScript code being linted

The "tslint:all" rules give a : "no-unused-variable is deprecated. Since TypeScript 2.9. Please use the built-in compiler checks instead."

with tslint.json configuration:

{
    "extends": [
        "tslint:all"
    ],
    "defaultSeverity": "error",
    "rules": {
        "completed-docs": false,
        "prefer-for-of": false,
        "strict-type-predicates": false,
        "only-arrow-functions": [
            true,
            "allow-named-functions"
        ],
        "no-inferrable-types": [
            false,
            "ignore-params",
            "ignore-properties"
        ],
        "max-line-length": [
            false,
            170
        ],
        "align": [
            false
        ],
        "no-unnecessary-type-assertion": false,
        "prefer-switch": false
    }
}

[kachkaev]

I'm also not sure why I'm seeing the deprecation warning given that "no-unused-variable" has been un-deprecated in #2256. 🤔

yarn tsc --version
# 2.9.2
yarn tslint --version
# 5.11.0

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

tslint.json

{
  "extends": ["tslint:recommended", "tslint-config-prettier"],
  "rules": {
    "interface-name": [true, "never-prefix"],
    "no-console": false,
    "no-unused-variable": {"severity": "warning"},
    "object-literal-sort-keys": false
  }
}

---

It sometimes makes sence to use "no-unused-variable": {"severity": "warning"} rather than going for "noUnusedLocals" / "noUnusedParameters" in tsconfig.json. When you are developing something quick and dirty, you do want things to compile even when they are not ideal, yet get some gentle feedback as you edit the stuff.

[howardjing]

It looks like it was redeprecated in release 5.11.0 as per the changelog: https://github.com/palantir/tslint/blob/master/CHANGELOG.md#warning-deprecations

[johnwiseheart]

The deprecation is intentional. Please see #3919 for details.

[realtebo]

So, now how to get rid of this warning?

"tslint": "^5.11.0",
"typescript": "^3.0.1"

> tslint --project tsconfig.json

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

ans this the config json

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

I suggest to add at least a tip of what to do to fix, because in my config this rules is not present.

[kachkaev]

The warning comes from tslint.json rather than tsconfig.json. Check if you have "no-unused-variable" right in there or in any of configs declared in "extends".

[realtebo]

I removed from tslint.json and .eslintrc.json.

Warning is still here. How to 'mute' it?

This demonstrate that a warning need additional infos to be usefull to users because not every dev know where it come from. I am one of them.

[franzisk]

Just let your tsling.json like this:

{
  "rules": {
    "no-duplicate-variable": true
  },
  "rulesDirectory": [
    "node_modules/tslint-eslint-rules/dist/rules"
  ]
}

[andyfleming]

I agree with @kachkaev that having a compilation failure is very annoying during active development. Linting is specifically where I want to catch this issue.

[ghost]

I want this rule so I can use --fix and fix it automatically.

[adidahiya]

continue discussion in #4100