no-unused-vars with ignoreRestSiblings:true reports false-positives

Tell us about your environment

• ESLint Version: 7.21.0
• Node Version: 12.16.2
• npm Version: 6.14.4
• Operating System: Windows

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using? babel-eslint

Please show your full configuration:

Configuration

module.exports = {
    extends: 'airbnb',
    parser: 'babel-eslint',
    plugins: [
        'jasmine',
        'webdriverio',
        'react-redux',
    ],
    env: {
        'browser': true,
        'node': true,
        'jasmine': true,
        'webdriverio/wdio': true,
    },
    rules: {
        'import/no-cycle': 'off',
        'react/jsx-props-no-spreading': 'off',
        'react/no-access-state-in-setstate': 'off',
        'arrow-parens': ['error', "as-needed", { "requireForBlockBody": true }],
        'function-paren-newline': 'off',
        'indent': ['error', 4, { 'SwitchCase': 1 }],
        'no-undef': 'error',
        'no-underscore-dangle': 'off',
        'no-multiple-empty-lines': ['warn', { "max": 2 } ],
        'no-else-return': ['error', { allowElseIf: true }],
        'no-restricted-globals': [
            "error",
            { name: 'Set', message: 'Use window.Set or add an eslint-ignore if native Set is what you want' },
            { name: 'Map', message: 'Use window.Map or add an eslint-ignore if native Map is what you want' }
        ],
        'max-len': ['error', 120],
        'implicit-arrow-linebreak': 'off',
        'jsx-a11y/click-events-have-key-events': 'off',
        'jsx-a11y/interactive-supports-focus': 'off',
        'jsx-a11y/label-has-for': 'off',
        'jsx-a11y/label-has-associated-control': 'off',
        'jsx-a11y/no-noninteractive-element-interactions': 'off',
        'jsx-a11y/no-static-element-interactions': 'off',
        'jsx-a11y/anchor-is-valid': 'off',
        'jsx-a11y/control-has-associated-label': 'off',
        'class-methods-use-this': 'off',
        'no-plusplus': ['error', { 'allowForLoopAfterthoughts': true }],
        'no-mixed-operators': ['error', { 'allowSamePrecedence': true }],
        'no-multi-spaces': ['error', { ignoreEOLComments: true }],
        'no-console': 'warn',
        'no-continue': 'off',
        'no-unused-vars': ['error', { 'ignoreRestSiblings': true }],
        'object-curly-newline': 'off',
        'operator-linebreak': ["warn", "after"],
        'prefer-destructuring': 'off',
        'prefer-promise-reject-errors': 'warn',
        'react/sort-comp': ['warn', { order: ['static-methods',  'lifecycle', 'everything-else', 'render'] }],
        'react/forbid-prop-types': 'off',
        'react/jsx-fragments': 'off',
        'react/jsx-filename-extension': 'off',
        'react/jsx-indent': ['error', 4],
        'react/jsx-indent-props': ['error', 4],
        'react/no-danger': 'off',
        'react/require-default-props': 'off',
        'react/jsx-boolean-value': 'off',
        'react/no-did-update-set-state': 'off', // recommended way since 16.3.
        'react/destructuring-assignment': 'off',
        'react/static-property-placement': 'off',
        'react-redux/prefer-separate-component-file': 'off',
        'react-redux/connect-prefer-named-arguments': 'off',
        'react/no-unused-prop-types': 'off', // superseded by react-redux/no-unused-prop-types
        'react/jsx-props-no-multi-spaces': 'off',
        // disallow certain syntax forms
        // http://eslint.org/docs/rules/no-restricted-syntax
        'no-restricted-syntax': [
            'error',
            {
                selector: 'ForInStatement',
                message: 'for..in loops iterate over the entire prototype chain, which is virtually never what you want. Use Object.{keys,values,entries}, and iterate over the resulting array.',
            },
            {
                selector: 'LabeledStatement',
                message: 'Labels are a form of GOTO; using them makes code confusing and hard to maintain and understand.',
            },
            {
                selector: 'WithStatement',
                message: '`with` is disallowed in strict mode because it makes code impossible to predict and optimize.',
            },
        ],
        camelcase: 'off'
    },
    globals: {
        '__BUILD_NR__': true,
        'requestIdleCallback': true,
        'any': true
    },
    settings: {
        'import/core-modules': [
            'native-api',
        ],
        'react': {
            'pragma': 'React',
            'version': '16.3'
        },
    }
};

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

function buildLibraryStructure(folders, entries) {
    const structureMap = {
        root: {
            id: 'root',
            title: 'Library',
            type: navItemTypes.folder,
            parent: null,
            children: [],
            weight: 1,
        },
    };

    // reused dummy variables used to spread data out of entries/folders
    /* eslint-disable no-unused-vars */
    let folder;
    let validFrom;
    let validUntil;
    let parent;
    /* eslint-enable no-unused-vars */
    let rest;

    // Add folders to map of items
    folders.forEach((folderItem) => {
        ({ folder, validFrom, validUntil, ...rest } = folderItem);

        structureMap[folderItem.id] = {
            ...rest,
            oid: folderItem.id,
            isFolder: true,
        };
    });
    return structureMap;
}

What did you expect to happen? I believe the rule no-unused-vars should not be triggered.

The rule is configured as 'no-unused-vars': ['error', { 'ignoreRestSiblings': true }],. The above code splits definition and spreading of the two variables folder and rest. The definition of the variables are even enclosed in a disable no-unused-vars

What actually happened? Please copy-paste the actual, raw output from ESLint.

38:16 error ‘folder’ is assigned a value but never used no-unused-vars 38:20 error ‘validFrom’ is assigned a value but never used no-unused-vars 38:31 error ‘validUntil’ is assigned a value but never used no-unused-vars

Steps to reproduce this issue:

1. split definition and usage of variables
2. use the rest operator with a throw-away variables on an other line
3. no-unsed-vars is triggered

Are you willing to submit a pull request to fix this bug? No, I don’t think I could

[LulaV14]

My apologies @nzakas I’ve been very busy lately and haven’t put a PR for this. I see there’s an open PR created by @yeonjuan that should fix the issue.

I’ll try checking other good first-time issues.

[yeonjuan]

Hi @LulaV14. Sorry for doing it without checking your progress. I should have checked but I missed it…😭