no-unused-variable doesn't work in declaration files

[karol-majewski]

Bug Report

• TSLint version: 5.10.0
• TypeScript version: 2.8.3
• Running TSLint via: CLI

TypeScript code being linted

a.ts

export const name = "John";
export const surname = "Doe";

b.d.ts

import { name, surname } from "./a";

export { name };

with tslint.json configuration:

{
  "extends": [
    "tslint:latest"
  ],
  "rules": {
    "no-unused-variable": true
  }
}

Actual behavior

No error.

Expected behavior

Error: 'surname' is declared but its value is never read.

[giladgray]

@karol-majewski what happens in the original b.ts source file? does it use surname in a way that is not preserved in the output? if not, then this behavior is expected.

[giladgray]

basically, this behavior looks correct. TSLint treats .d.ts files as source code unless you exclude/ignore them. so the lint rule is catching a valid error.

oops i think i read this backwards!

[karol-majewski]

@giladgray It does not use it in any way.

This becomes problematic when you import and export from & to .d.ts files (your application domain model for example) and you end up with dead code pilling up, with no way to manage it.

[JoshuaKGoldberg]

Amusing: this is the opposite of requests such as #190 and #434. Imports and types do seem reasonable to not exclude for being declarations.

[JoshuaKGoldberg]

💀 It's time! 💀

TSLint is deprecated and no longer accepting pull requests other than security fixes. See #4534. ☠️
We recommend you instead use typescript-eslint to lint your TypeScript code with ESLint. ✅

👋 It was a pleasure open sourcing with you!

[JoshuaKGoldberg]

🤖 Beep boop! 👉 TSLint is deprecated 👈 (#4534) and you should switch to typescript-eslint! 🤖

🔒 This issue is being locked to prevent further unnecessary discussions. Thank you! 👋