"comma-style" doesn't like ignored, multiline destructured array elements.

Tell us about your environment

• ESLint Version: 6.8.0
• Node Version: 13.6.0
• NPM Version: 6.13.4
• Parser @typescript-eslint

Please show your full configuration:

Configuration

```js module.exports = { env: { browser: true, node: true, es6: true, }, extends: [ 'airbnb', 'plugin:react/recommended', 'plugin:import/typescript', ], globals: { PropTypes: false, React: false, uiVersion: false, }, parser: '@typescript-eslint/parser', parserOptions: { ecmaFeatures: { jsx: true, }, ecmaVersion: 2018, sourceType: 'module', }, plugins: [ '@typescript-eslint', 'react', 'react-hooks', 'sort-destructure-keys', ], rules: { 'array-bracket-newline': ['error', { 'multiline': true, 'minItems': 3, }], 'array-element-newline': ['warn', { 'multiline': true, 'minItems': 3, }], 'arrow-body-style': 'off', 'arrow-parens': 'off', 'camelcase': ['warn', { allow: ["^UNSAFE_", "doc_count", "^active_"], }], 'comma-dangle': ['warn', 'always-multiline'], 'consistent-return': ['warn', { treatUndefinedAsUnspecified: true }], 'func-names': ['warn', 'as-needed'], 'function-paren-newline': ['warn', 'consistent'], 'implicit-arrow-linebreak': 'off', 'indent': ['warn', 4, { ArrayExpression: 'first', CallExpression: { arguments: 'first' }, flatTernaryExpressions: true, FunctionDeclaration: { parameters: 'first' }, FunctionExpression: { parameters: 'first' }, ignoreComments: true, ignoredNodes: [ 'ConditionalExpression', 'JSXAttribute', 'JSXClosingElement', 'JSXElement', 'JSXElement > *', 'JSXEmptyExpression', 'JSXExpressionContainer', 'JSXIdentifier', 'JSXMemberExpression', 'JSXNamespacedName', 'JSXOpeningElement', 'JSXSpreadAttribute', 'JSXSpreadChild', 'JSXText', 'TemplateLiteral > *', ], ImportDeclaration: 'first', MemberExpression: 1, ObjectExpression: 'first', SwitchCase: 1, VariableDeclarator: 'first', }], 'multiline-ternary': ['warn', 'always-multiline'], 'no-console': ['warn', { allow: [ 'info', 'warn', 'error', ] }], 'no-debugger': 'warn', 'no-fallthrough': ['warn', { commentPattern: 'break[\\s\\w]*omitted', }], 'no-nested-ternary': 'off', 'no-unneeded-ternary': 'warn', 'no-unused-expressions': ['warn', { allowShortCircuit: true, allowTaggedTemplates: true, allowTernary: true, }], 'no-var': 'error', // Must use const or let. 'object-property-newline': ['warn', { // allowAllPropertiesOnSameLine: false, }], 'object-curly-newline': 'warn', // ['warn', { // ObjectExpression: { // 'multiline': true, // 'minProperties': 2, // }, // ObjectPattern: { // 'multiline': true, // 'minProperties': 2, // }, // ImportDeclaration: { // 'multiline': true, // 'minProperties': 2, // }, // ExportDeclaration: { // 'multiline': true, // 'minProperties': 2, // }, // }], 'operator-linebreak': ['warn', 'after', { overrides: { '?': 'before', ':': 'before', } }], 'padded-blocks': 'error', 'semi': ['warn', 'always'], 'sort-keys': ['warn', 'asc', { caseSensitive: false, natural: true, }], 'quotes': ['warn', 'single'], 'import/extensions': 'off', 'react/jsx-closing-bracket-location': ['warn', 'props-aligned'], 'react/jsx-filename-extension': ['warn', { extensions: [ '.js', '.jsx', '.tsx', ], }], 'react/jsx-first-prop-new-line': ['warn', 'multiline'], 'react/jsx-fragments': ['error', 'element'], 'react/jsx-indent': ['warn', 2, { checkAttributes: true, indentLogicalExpressions: true, }], 'react/jsx-indent-props': ['warn', 2], 'react/jsx-max-props-per-line': ['warn', { maximum: 1, when: 'multiline', }], 'react/jsx-one-expression-per-line': ['warn', { allow: 'single-child', }], 'react/jsx-sort-default-props': 'error', 'react/jsx-sort-props': ['warn', { ignoreCase: true, }], 'react/jsx-tag-spacing': ['warn', { closingSlash: 'never', beforeSelfClosing: 'always', afterOpening: 'never', beforeClosing: 'never', }], 'react/jsx-wrap-multilines': ['error', { declaration: 'parens-new-line', assignment: 'parens-new-line', return: 'parens-new-line', arrow: 'parens-new-line', condition: 'parens-new-line', logical: 'parens-new-line', prop: 'parens-new-line', }], 'react/no-did-mount-set-state': 'warn', 'react/no-did-update-set-state': 'warn', 'react/no-direct-mutation-state': 'warn', 'react/no-multi-comp': 'warn', 'react/no-unknown-property': 'warn', 'react/sort-comp': 'warn', 'react/sort-prop-types': 'error', 'react/prop-types': 'off', 'sort-destructure-keys/sort-destructure-keys': ['warn', { caseSensitive: false, }], '@typescript-eslint/explicit-function-return-type': 'off', '@typescript-eslint/explicit-member-accessibility': 'off', }, settings: { 'import/resolver': { node: { paths: ['./src/packages'] }, }, react: { version: 'detect', }, }, } ```

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

Tried destructuring an array, while ignoring the first two elements (as per MDN). Expecting each element in a new line (my preference to ease code version management, discussion for another day), somehow the second comma is not happy unless the whole destructuring assignment is in a single line.

const [
    ,,
    configPath = 'config.json',
    authFilePath = 'freshbooks.auth',
] = process.argv;

const [
    ,
    ,
    configPath = 'config.json',
    authFilePath = 'freshbooks.auth',
] = process.argv;

In both cases I get a Bad line breaking before and after ','. (comma-style) error message for the second comma.

Thought I’d use the “ArrayPattern” exception, but that would turn linting off for all array destructuring, and that’s less desirable. Seems to me like the rule should understand ignored elements (bug), or we should have another exception/handling for these consecutive commas. Running ESLint automatically, using linter-eslint on Atom.

Thoughts?

While looking for other issues like this, and found a couple closed ones:

• https://github.com/eslint/eslint/issues/1587 adds a fix, yet doesn’t address multiline code.
• https://github.com/eslint/eslint/issues/9968 closed without resolution, doesn’t deal with multiline either.

Are you willing to submit a pull request to fix this bug? Likely yes, if someone points me in the right direction (inside the repo).

[kaicataldo]

I agree that this seems like a bug. Seems like we want to add some special logic for ArrayPatterns (code can be found here) that accounts for lines that contain ignored destructured array elements. I imagine we want to essentially ignore any lines that are only made of commas. It looks like we’ll have to do it at the token level because empty destructured elements are represented as null in the AST.

[boutahlilsoufiane]

I’m going to do this.