"no-unused-vars" cannot report all parameters of function

Tell us about your environment

• ESLint Version: 4.13.1
• Node Version: 8.9.3

What parser (default, Babel-ESLint, etc.) are you using? default

Please show your full configuration:

Configuration

{
  "parserOptions": {
    "ecmaVersion": 2017,
    "sourceType": "module",
    "ecmaFeatures": {
      "jsx": true
    }
  },
  "env": {
    "es6": true,
    "node": true
  },
  "plugins": [
    "import",
    "eslint-comments"
  ],
  "rules": {
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    "no-cond-assign": [2, "except-parens"],
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    "no-extra-boolean-cast": 2,
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      "conditionalAssign": false,
      "returnAssign": false,
      "nestedBinaryExpressions": false,
      "ignoreJSX": "multi-line",
      "enforceForArrowConditionals": false
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    "import/no-unresolved": [2, { "ignore": ["^@"] }],
    "import/named": 1,
    "import/default": 2,
    "import/namespace": 2,
    "import/no-absolute-path": 2,
    "import/no-dynamic-require": 1,
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    "import/no-named-as-default": 2,
    "import/no-named-as-default-member": 1,
    "import/no-deprecated": 1,
    "import/no-extraneous-dependencies": [2, { "devDependencies": ["**/*.test.js", "**/*.spec.js"] }],
    "import/first": 2,
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    "eslint-comments/disable-enable-pair": [1, { "allowWholeFile": true }],
    "eslint-comments/no-aggregating-enable": 1,
    "eslint-comments/no-duplicate-disable": 1,
    "eslint-comments/no-unused-disable": 1,
    "eslint-comments/no-unused-enable": 1
  }
}

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

Define a function which it has several unused parameters.

function fn (a, b, c) {
  // do nothing
}
fn()

What did you expect to happen?

For the example above, ESLint should report all parameters is unused.

What actually happened? Please include the actual, raw output from ESLint.

ESLint just reported the last parameter (for the example above that is c) is unused, previous parameters haven’t been reported.

[platinumazure]

I’ll champion.

@eslint/eslint-team Could we get two more 👍s? Right now, no-unused-vars reports only the last parameter that is unused, even if earlier parameters are also unused. This is confusing and inconsistent with how we generally implement other rules and I think it needs to change.

[platinumazure]

I’ve run my examples through the ESLint demo page.

Everything looks good on the “all” setting.

For the “after-used” setting, I think the first two examples have a bug (only c is reported in the first example, and only e is reported in the second example).

So I’m now absolutely convinced we have a bug here.