.eslintrc.js

/*
 * IMPORTANT!
 *
 * Any changes made to this file must also be made to eslint.config.js.
 *
 * Internally, ESLint is using the eslint.config.js file to lint itself.
 * This file is needed too, because:
 *
 * 1. ESLint VS Code extension expects eslintrc config files to be
 *    present to work correctly.
 *
 * Once we no longer need to support both eslintrc and flat config, we will
 * remove this file.
 */


"use strict";

const path = require("node:path");

const INTERNAL_FILES = {
    CLI_ENGINE_PATTERN: "lib/cli-engine/**/*",
    LINTER_PATTERN: "lib/linter/**/*",
    RULE_TESTER_PATTERN: "lib/rule-tester/**/*",
    RULES_PATTERN: "lib/rules/**/*",
    SOURCE_CODE_PATTERN: "lib/source-code/**/*"
};

/**
 * Resolve an absolute path or glob pattern.
 * @param {string} pathOrPattern the path or glob pattern.
 * @returns {string} The resolved path or glob pattern.
 */
function resolveAbsolutePath(pathOrPattern) {
    return path.resolve(__dirname, pathOrPattern);
}

/**
 * Create an array of `no-restricted-require` entries for ESLint's core files.
 * @param {string} [pattern] The glob pattern to create the entries for.
 * @returns {Object[]} The array of `no-restricted-require` entries.
 */
function createInternalFilesPatterns(pattern = null) {
    return Object.values(INTERNAL_FILES)
        .filter(p => p !== pattern)
        .map(p => ({
            name: [

                // Disallow all children modules.
                resolveAbsolutePath(p),

                // Allow the main `index.js` module.
                `!${resolveAbsolutePath(p.replace(/\*\*\/\*$/u, "index.js"))}`
            ]
        }));
}

module.exports = {
    root: true,
    reportUnusedDisableDirectives: true,
    plugins: [
        "eslint-plugin",
        "internal-rules",
        "unicorn"
    ],
    extends: [
        "eslint:recommended",
        "plugin:n/recommended",
        "plugin:jsdoc/recommended",
        "plugin:@eslint-community/eslint-comments/recommended"
    ],
    settings: {
        jsdoc: {
            mode: "typescript",
            tagNamePreference: {
                file: "fileoverview",
                augments: "extends",
                class: "constructor"
            },
            preferredTypes: {
                "*": {
                    message:
                        "Use a more precise type or if necessary use `any` or `ArbitraryCallbackResult`",
                    replacement: "any"
                },
                Any: {
                    message:
                        "Use a more precise type or if necessary use `any` or `ArbitraryCallbackResult`",
                    replacement: "any"
                },
                function: {
                    message:
                        "Point to a `@callback` namepath or `Function` if truly arbitrary in form",
                    replacement: "Function"
                },
                Promise: {
                    message:
                        "Specify the specific Promise type, including, if necessary, the type `any`"
                },
                ".<>": {
                    message: "Prefer type form without dot",
                    replacement: "<>"
                },
                object: {
                    message:
                        "Use the specific object type or `Object` if truly arbitrary",
                    replacement: "Object"
                },
                array: "Array"
            }
        }
    },
    parserOptions: {
        ecmaVersion: "latest"
    },
    rules: {
        "internal-rules/multiline-comment-style": "error",
        "array-bracket-spacing": "error",
        "array-callback-return": "error",
        "arrow-body-style": ["error", "as-needed"],
        "arrow-parens": ["error", "as-needed"],
        "arrow-spacing": "error",
        indent: [
            "error",
            4,
            {
                SwitchCase: 1
            }
        ],
        "block-spacing": "error",
        "brace-style": ["error", "1tbs"],
        camelcase: "error",
        "class-methods-use-this": "error",
        "comma-dangle": "error",
        "comma-spacing": "error",
        "comma-style": ["error", "last"],
        "computed-property-spacing": "error",
        "consistent-return": "error",
        curly: ["error", "all"],
        "default-case": "error",
        "default-case-last": "error",
        "default-param-last": "error",
        "dot-location": ["error", "property"],
        "dot-notation": [
            "error",
            {
                allowKeywords: true
            }
        ],
        "eol-last": "error",
        eqeqeq: "error",
        "@eslint-community/eslint-comments/disable-enable-pair": ["error"],
        "@eslint-community/eslint-comments/no-unused-disable": "error",
        "@eslint-community/eslint-comments/require-description": "error",
        "func-call-spacing": "error",
        "func-style": ["error", "declaration"],
        "function-call-argument-newline": ["error", "consistent"],
        "function-paren-newline": ["error", "consistent"],
        "generator-star-spacing": "error",
        "grouped-accessor-pairs": "error",
        "guard-for-in": "error",
        "jsdoc/check-syntax": "error",
        "jsdoc/check-values": [
            "error",
            {
                allowedLicenses: true
            }
        ],
        "jsdoc/no-bad-blocks": "error",
        "jsdoc/no-defaults": "off",
        "jsdoc/require-asterisk-prefix": "error",
        "jsdoc/require-description": [
            "error",
            {
                checkConstructors: false
            }
        ],
        "jsdoc/require-hyphen-before-param-description": ["error", "never"],
        "jsdoc/require-returns": [
            "error",
            {
                forceRequireReturn: true,
                forceReturnsWithAsync: true
            }
        ],
        "jsdoc/require-throws": "error",
        "jsdoc/tag-lines": [
            "error",
            "never",
            {
                tags: {
                    example: {
                        lines: "always"
                    },
                    fileoverview: {
                        lines: "any"
                    }
                },
                startLines: 0
            }

        ],
        "jsdoc/no-undefined-types": "off",
        "jsdoc/require-yields": "off",
        "jsdoc/check-access": "error",
        "jsdoc/check-alignment": "error",
        "jsdoc/check-param-names": "error",
        "jsdoc/check-property-names": "error",
        "jsdoc/check-tag-names": "error",
        "jsdoc/check-types": "error",
        "jsdoc/empty-tags": "error",
        "jsdoc/implements-on-classes": "error",
        "jsdoc/multiline-blocks": "error",
        "jsdoc/no-multi-asterisks": ["error", { allowWhitespace: true }],
        "jsdoc/require-jsdoc": [
            "error",
            {
                require: {
                    ClassDeclaration: true
                }
            }
        ],
        "jsdoc/require-param": "error",
        "jsdoc/require-param-description": "error",
        "jsdoc/require-param-name": "error",
        "jsdoc/require-param-type": "error",
        "jsdoc/require-property": "error",
        "jsdoc/require-property-description": "error",
        "jsdoc/require-property-name": "error",
        "jsdoc/require-property-type": "error",
        "jsdoc/require-returns-check": "error",
        "jsdoc/require-returns-description": "error",
        "jsdoc/require-returns-type": "error",
        "jsdoc/require-yields-check": "error",
        "jsdoc/valid-types": "error",
        "key-spacing": [
            "error",
            {
                beforeColon: false,
                afterColon: true
            }
        ],
        "keyword-spacing": "error",
        "lines-around-comment": [
            "error",
            {
                beforeBlockComment: true,
                afterBlockComment: false,
                beforeLineComment: true,
                afterLineComment: false
            }
        ],
        "max-len": [
            "error",
            160,
            {
                ignoreComments: true,
                ignoreUrls: true,
                ignoreStrings: true,
                ignoreTemplateLiterals: true,
                ignoreRegExpLiterals: true
            }
        ],
        "max-statements-per-line": "error",
        "new-cap": "error",
        "new-parens": "error",
        "no-alert": "error",
        "no-array-constructor": "error",
        "no-caller": "error",
        "no-confusing-arrow": "error",
        "no-console": "error",
        "no-constant-binary-expression": "error",
        "no-constructor-return": "error",
        "no-else-return": [
            "error",
            {
                allowElseIf: false
            }
        ],
        "no-eval": "error",
        "no-extend-native": "error",
        "no-extra-bind": "error",
        "no-extra-semi": "error",
        "no-floating-decimal": "error",
        "no-implied-eval": "error",
        "no-inner-declarations": "error",
        "no-invalid-this": "error",
        "no-iterator": "error",
        "no-label-var": "error",
        "no-labels": "error",
        "no-lone-blocks": "error",
        "no-loop-func": "error",
        "no-mixed-spaces-and-tabs": ["error", false],
        "no-multi-spaces": "error",
        "no-multi-str": "error",
        "no-multiple-empty-lines": [
            "error",
            {
                max: 2,
                maxBOF: 0,
                maxEOF: 0
            }
        ],
        "no-nested-ternary": "error",
        "no-new": "error",
        "no-new-func": "error",
        "no-new-object": "error",
        "no-new-wrappers": "error",
        "no-octal-escape": "error",
        "no-param-reassign": "error",
        "no-proto": "error",
        "no-process-exit": "off",
        "no-restricted-properties": [
            "error",
            {
                property: "substring",
                message: "Use .slice instead of .substring."
            },
            {
                property: "substr",
                message: "Use .slice instead of .substr."
            },
            {
                object: "assert",
                property: "equal",
                message: "Use assert.strictEqual instead of assert.equal."
            },
            {
                object: "assert",
                property: "notEqual",
                message:
                    "Use assert.notStrictEqual instead of assert.notEqual."
            },
            {
                object: "assert",
                property: "deepEqual",
                message:
                    "Use assert.deepStrictEqual instead of assert.deepEqual."
            },
            {
                object: "assert",
                property: "notDeepEqual",
                message:
                    "Use assert.notDeepStrictEqual instead of assert.notDeepEqual."
            }
        ],
        "no-return-assign": "error",
        "no-script-url": "error",
        "no-self-compare": "error",
        "no-sequences": "error",
        "no-shadow": "error",
        "no-tabs": "error",
        "no-throw-literal": "error",
        "no-trailing-spaces": "error",
        "no-undef": [
            "error",
            {
                typeof: true
            }
        ],
        "no-undef-init": "error",
        "no-undefined": "error",
        "no-underscore-dangle": [
            "error",
            {
                allowAfterThis: true
            }
        ],
        "no-unmodified-loop-condition": "error",
        "no-unneeded-ternary": "error",
        "no-unreachable-loop": "error",
        "no-unused-expressions": "error",
        "no-unused-vars": [
            "error",
            {
                vars: "all",
                args: "after-used",
                caughtErrors: "all"
            }
        ],
        "no-use-before-define": "error",
        "no-useless-assignment": "error",
        "no-useless-call": "error",
        "no-useless-computed-key": "error",
        "no-useless-concat": "error",
        "no-useless-constructor": "error",
        "no-useless-rename": "error",
        "no-useless-return": "error",
        "no-whitespace-before-property": "error",
        "no-var": "error",
        "n/callback-return": ["error", ["cb", "callback", "next"]],
        "n/handle-callback-err": ["error", "err"],
        "n/no-deprecated-api": "error",
        "n/no-mixed-requires": "error",
        "n/no-new-require": "error",
        "n/no-path-concat": "error",
        "object-curly-newline": [
            "error",
            {
                consistent: true,
                multiline: true
            }
        ],
        "object-curly-spacing": ["error", "always"],
        "object-property-newline": [
            "error",
            {
                allowAllPropertiesOnSameLine: true
            }
        ],
        "object-shorthand": [
            "error",
            "always",
            {
                avoidExplicitReturnArrows: true
            }
        ],
        "one-var-declaration-per-line": "error",
        "operator-assignment": "error",
        "operator-linebreak": "error",
        "padding-line-between-statements": [
            "error",
            {
                blankLine: "always",
                prev: ["const", "let", "var"],
                next: "*"
            },
            {
                blankLine: "any",
                prev: ["const", "let", "var"],
                next: ["const", "let", "var"]
            }
        ],
        "prefer-arrow-callback": "error",
        "prefer-const": "error",
        "prefer-exponentiation-operator": "error",
        "prefer-numeric-literals": "error",
        "prefer-object-has-own": "error",
        "prefer-promise-reject-errors": "error",
        "prefer-regex-literals": "error",
        "prefer-rest-params": "error",
        "prefer-spread": "error",
        "prefer-template": "error",
        quotes: [
            "error",
            "double",
            {
                avoidEscape: true
            }
        ],
        "quote-props": ["error", "as-needed"],
        radix: "error",
        "require-unicode-regexp": "error",
        "rest-spread-spacing": "error",
        semi: "error",
        "semi-spacing": [
            "error",
            {
                before: false,
                after: true
            }
        ],
        "semi-style": "error",
        "space-before-blocks": "error",
        "space-before-function-paren": [
            "error",
            {
                anonymous: "never",
                named: "never",
                asyncArrow: "always"
            }
        ],
        "space-in-parens": "error",
        "space-infix-ops": "error",
        "space-unary-ops": [
            "error",
            {
                words: true,
                nonwords: false
            }
        ],
        "spaced-comment": [
            "error",
            "always",
            {
                exceptions: ["-"]
            }
        ],
        strict: ["error", "global"],
        "switch-colon-spacing": "error",
        "symbol-description": "error",
        "template-curly-spacing": ["error", "never"],
        "template-tag-spacing": "error",
        "unicode-bom": "error",
        "unicorn/prefer-array-find": "error",
        "unicorn/prefer-array-flat-map": "error",
        "unicorn/prefer-array-flat": "error",
        "unicorn/prefer-array-index-of": "error",
        "unicorn/prefer-array-some": "error",
        "unicorn/prefer-at": "error",
        "unicorn/prefer-includes": "error",
        "unicorn/prefer-set-has": "error",
        "unicorn/prefer-string-slice": "error",
        "unicorn/prefer-string-starts-ends-with": "error",
        "unicorn/prefer-string-trim-start-end": "error",
        "wrap-iife": "error",
        "yield-star-spacing": "error",
        yoda: [
            "error",
            "never",
            {
                exceptRange: true
            }
        ]
    },
    overrides: [
        {
            files: ["tools/*.js", "docs/tools/*.js"],
            rules: {
                "no-console": "off",
                "n/no-process-exit": "off"
            }
        },
        {
            files: ["lib/rules/*", "tools/internal-rules/*"],
            excludedFiles: ["index.js"],
            extends: [
                "plugin:eslint-plugin/rules-recommended"
            ],
            rules: {
                "eslint-plugin/prefer-placeholders": "error",
                "eslint-plugin/prefer-replace-text": "error",
                "eslint-plugin/report-message-format": ["error", "[^a-z].*\\.$"],
                "eslint-plugin/require-meta-docs-description": ["error", { pattern: "^(Enforce|Require|Disallow) .+[^. ]$" }],
                "internal-rules/no-invalid-meta": "error"
            }
        },
        {
            files: ["lib/rules/*"],
            excludedFiles: ["index.js"],
            rules: {
                "eslint-plugin/require-meta-docs-url": ["error", { pattern: "https://eslint.org/docs/latest/rules/{{name}}" }]
            }
        },
        {
            files: ["tests/lib/rules/*", "tests/tools/internal-rules/*"],
            extends: [
                "plugin:eslint-plugin/tests-recommended"
            ],
            rules: {
                "eslint-plugin/test-case-property-ordering": [
                    "error",
                    [
                        "name",
                        "filename",
                        "code",
                        "output",
                        "options",
                        "languageOptions",
                        "errors"
                    ]
                ],
                "eslint-plugin/test-case-shorthand-strings": "error"
            }
        },
        {
            files: ["tests/**/*"],
            env: { mocha: true },
            rules: {
                "no-restricted-syntax": ["error", {
                    selector: "CallExpression[callee.object.name='assert'][callee.property.name='doesNotThrow']",
                    message: "`assert.doesNotThrow()` should be replaced with a comment next to the code."
                }]
            }
        },

        // Restrict relative path imports
        {
            files: ["lib/*"],
            excludedFiles: ["lib/unsupported-api.js"],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns()
                ]]
            }
        },
        {
            files: [INTERNAL_FILES.CLI_ENGINE_PATTERN],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns(INTERNAL_FILES.CLI_ENGINE_PATTERN)
                ]]
            }
        },
        {
            files: [INTERNAL_FILES.LINTER_PATTERN],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns(INTERNAL_FILES.LINTER_PATTERN),
                    "fs",
                    resolveAbsolutePath("lib/cli-engine/index.js"),
                    resolveAbsolutePath("lib/rule-tester/index.js")
                ]]
            }
        },
        {
            files: [INTERNAL_FILES.RULES_PATTERN],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns(INTERNAL_FILES.RULES_PATTERN),
                    "fs",
                    resolveAbsolutePath("lib/cli-engine/index.js"),
                    resolveAbsolutePath("lib/linter/index.js"),
                    resolveAbsolutePath("lib/rule-tester/index.js"),
                    resolveAbsolutePath("lib/source-code/index.js")
                ]]
            }
        },
        {
            files: ["lib/shared/**/*"],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns(),
                    resolveAbsolutePath("lib/cli-engine/index.js"),
                    resolveAbsolutePath("lib/linter/index.js"),
                    resolveAbsolutePath("lib/rule-tester/index.js"),
                    resolveAbsolutePath("lib/source-code/index.js")
                ]]
            }
        },
        {
            files: [INTERNAL_FILES.SOURCE_CODE_PATTERN],
            rules: {
                "n/no-restricted-require": ["error", [
                    ...createInternalFilesPatterns(INTERNAL_FILES.SOURCE_CODE_PATTERN),
                    "fs",
                    resolveAbsolutePath("lib/cli-engine/index.js"),
                    resolveAbsolutePath("lib/linter/index.js"),
                    resolveAbsolutePath("lib/rule-tester/index.js"),
                    resolveAbsolutePath("lib/rules/index.js")
                ]]
            }
        },
        {
            files: [INTERNAL_FILES.RULE_TESTER_PATTERN],
            rules: {
                "n/no-restricted-require": ["error", [
                    resolveAbsolutePath("lib/cli-engine/index.js")
                ]]
            }
        }
    ]
};