.eslintrc

{
    "root": true,

    "parser": "@typescript-eslint/parser",
    "parserOptions": {
        "sourceType": "module"
    },

    "plugins": [
        "jest",
        "@lwc/lwc-internal",
        "@typescript-eslint",
        "import"
    ],
    "extends": [
        "eslint:recommended",
        "plugin:@typescript-eslint/eslint-recommended"
    ],

    "env": {
        "es6": true
    },

    "rules": {
        "no-unused-vars": "off",
        "@typescript-eslint/no-unused-vars": [
            "error",
            { "argsIgnorePattern": "^_" }
        ],

        "block-scoped-var": "error",
        "no-alert": "error",
        "no-buffer-constructor": "error",
        "no-console": "error",
        "no-eval": "error",
        "no-extend-native": "error",
        "no-extra-bind": "error",
        "no-extra-label": "error",
        "no-iterator": "error",
        "no-lone-blocks": "error",
        "no-proto": "error",
        "no-prototype-builtins": "error",
        "no-new-require": "error",
        "no-restricted-properties": ["error", {
            "object": "arguments",
            "property": "callee",
            "message": "arguments.callee is deprecated"
        }, {
            "object": "global",
            "property": "isFinite",
            "message": "Please use Number.isFinite instead"
        }, {
            "object": "self",
            "property": "isFinite",
            "message": "Please use Number.isFinite instead"
        }, {
            "object": "window",
            "property": "isFinite",
            "message": "Please use Number.isFinite instead"
        }, {
            "object": "global",
            "property": "isNaN",
            "message": "Please use Number.isNaN instead"
        }, {
            "object": "self",
            "property": "isNaN",
            "message": "Please use Number.isNaN instead"
        }, {
            "object": "window",
            "property": "isNaN",
            "message": "Please use Number.isNaN instead"
        }, {
            "property": "__defineGetter__",
            "message": "Please use Object.defineProperty instead."
        }, {
            "property": "__defineSetter__",
            "message": "Please use Object.defineProperty instead."
        }, {
            "object": "Math",
            "property": "pow",
            "message": "Use the exponentiation operator (**) instead."
        }, {
            "object": "globalThis",
            "property": "lwcRuntimeFlags",
            "message": "Use the bare global lwcRuntimeFlags instead."
        }],
        "no-self-compare": "error",
        "no-undef-init": "error",
        "no-useless-computed-key": "error",
        "no-useless-return": "error",
        "prefer-const": ["error", {
            "destructuring": "any",
            "ignoreReadBeforeAssign": true
        }],
        "template-curly-spacing": "error",
        "yoda": "error",

        "@lwc/lwc-internal/no-invalid-todo": "error",
        "import/order": [
            "error",
            { "groups": ["builtin", "external", "internal", "parent", "index", "sibling", "object", "type"] }
        ],
        "no-restricted-imports": ["error", {
            "name": "@lwc/features",
            "importNames": ["lwcRuntimeFlags", "runtimeFlags", "default"],
            "message": "Do not directly import runtime flags from @lwc/features. Use the global lwcRuntimeFlags variable instead."
        }]
    },

    "overrides": [
        {
            "files": [
                "**/@lwc/engine-core/**",
                "**/@lwc/engine-dom/**",
                "**/@lwc/synthetic-shadow/**"
            ],
            "rules": {
                "@lwc/lwc-internal/no-global-node": "error",
                "prefer-rest-params": "off",
                "prefer-spread": "off"
            }
        },
        {
            "files": [
                "**/__tests__/**",
                "**/__mocks__/**",
                "**/@lwc/integration-karma/**"
            ],

            "env": {
                "jest": true,
                "es6": true,
                "es2017": true,
                "es2020": true
            },

            "rules": {
                "jest/no-focused-tests": "error",
                "jest/valid-expect": "error",
                "jest/valid-expect-in-promise": "error"
            }
        },
        {
            "files": [
                "**/@lwc/integration-tests/**"
            ],

            "globals": {
                "$": true,
                "browser": true
            }
        },
        {
            "files": [
                "./*.js",
                "**/scripts/**",
                "**/jest.config.js"
            ],

            "env": {
                "node": true,
                "jest": true
            },

            "rules": {
                "no-console": "off"
            }
        },
        {
            "files": [
                "**/perf-benchmarks/**"
            ],

            "globals": {
                "after": true,
                "before": true,
                "benchmark": true,
                "run": true
            }
        }
    ]
}