.eslintrc.js

// This file is the default configuration file for TypeScript Analyzer (ESLint)
// The default location in C# is something like c:\Users\{UserName}\TypeScriptAnalyzerConfig\.eslintrc.js

// If the prettierEnabled flag is set to false prettier is completely disabled, and the (less opinionated) set of ESLint formatting rules
// under prettierDisabledConfig below are enabled instead.  Delete these, or turn them off, if you want NO formatting rules in the linter.
const prettierEnabled = true;

const config = {
    "root": true,
    "ignorePatterns": [".eslintrc.js"],

    // We can lint almost any file extension with an appropriate plugin, so having rules that apply to them all makes little sense
    // Instead all rules are defined in overrides sections by file extension, even though we're not actually overriding anything
    "overrides": [
        {
            // This object has rules etc. that apply to BOTH JavaScript and TypeScript.
            // Rules that only apply to JavaScript are in a JavaScript object further below, and similarly for TypeScript.
            "files": ["*.js", "*.jsx", "*.mjs", "*.cjs", "*.ts", "*.tsx"],
            "parserOptions": {
                "ecmaVersion": 6,
                "sourceType": "module",
                "ecmaFeatures": {
                    "jsx": true, // Allows support of JSX, but use of React plugin is required to support React semantics
                },
            },
            // To disable a plugin commment it out here and also comment out its rules in the appropriate section below
            // Reverse that to enable one
            "plugins": [
                "@typescript-eslint",
                "prettier",
            ],
            "env": {
                "amd": true,
                "browser": true,
                "jquery": true,
                "node": true,
                "es6": true, // This enables ES6 global variables AND ES6 syntax
                "worker": true,
            },
            "rules": {
                // Below are all of the rules from eslint:recommended https://github.com/eslint/eslint/blob/master/conf/eslint-recommended.js,
                // apart from those that we want enabled for JavaScript only and not TypeScript, which are in the JavaScript object below
                // Options are off, warn, error (or 0, 1, 2 if you like meaningless numbers)
                // To add an option to a rule use [] e.g. "no-inner-declarations": ["error", "both"],
                // Full list of all rules: https://eslint.org/docs/rules/
                "for-direction": "error",                 // https://eslint.org/docs/rules/for-direction
                "no-async-promise-executor": "error",     // https://eslint.org/docs/rules/no-async-promise-executor
                "no-case-declarations": "error",          // https://eslint.org/docs/rules/no-case-declarations
                "no-class-assign": "error",               // https://eslint.org/docs/rules/no-class-assign
                "no-compare-neg-zero": "error",           // https://eslint.org/docs/rules/no-compare-neg-zero
                "no-cond-assign": "error",                // https://eslint.org/docs/rules/no-cond-assign
                "no-constant-condition": "error",         // https://eslint.org/docs/rules/no-constant-condition
                "no-control-regex": "error",              // https://eslint.org/docs/rules/no-control-regex
                "no-debugger": "error",                   // https://eslint.org/docs/rules/no-debugger
                "no-delete-var": "error",                 // https://eslint.org/docs/rules/no-delete-var
                "no-dupe-else-if": "error",               // https://eslint.org/docs/rules/no-dupe-else-if
                "no-duplicate-case": "error",             // https://eslint.org/docs/rules/no-duplicate-case
                "no-empty": "error",                      // https://eslint.org/docs/rules/no-empty
                "no-empty-character-class": "error",      // https://eslint.org/docs/rules/no-empty-character-class
                "no-empty-pattern": "error",              // https://eslint.org/docs/rules/no-empty-pattern
                "no-ex-assign": "error",                  // https://eslint.org/docs/rules/no-ex-assign
                "no-extra-boolean-cast": "error",         // https://eslint.org/docs/rules/no-extra-boolean-cast
                "no-fallthrough": "error",                // https://eslint.org/docs/rules/no-fallthrough
                "no-global-assign": "error",              // https://eslint.org/docs/rules/no-global-assign
                "no-inner-declarations": "error",         // https://eslint.org/docs/rules/no-inner-declarations
                "no-invalid-regexp": "error",             // https://eslint.org/docs/rules/no-invalid-regexp
                "no-irregular-whitespace": "error",       // https://eslint.org/docs/rules/no-irregular-whitespace
                "no-misleading-character-class": "error", // https://eslint.org/docs/rules/no-misleading-character-class
                "no-mixed-spaces-and-tabs": "error",      // https://eslint.org/docs/rules/no-mixed-spaces-and-tabs
                "no-nonoctal-decimal-escape": "error",    // https://eslint.org/docs/rules/no-nonoctal-decimal-escape
                "no-octal": "error",                      // https://eslint.org/docs/rules/no-octal
                "no-prototype-builtins": "error",         // https://eslint.org/docs/rules/no-prototype-builtins
                "no-regex-spaces": "error",               // https://eslint.org/docs/rules/no-regex-spaces
                "no-self-assign": "error",                // https://eslint.org/docs/rules/no-self-assign
                "no-shadow-restricted-names": "error",    // https://eslint.org/docs/rules/no-shadow-restricted-names
                "no-sparse-arrays": "error",              // https://eslint.org/docs/rules/no-sparse-arrays
                "no-unexpected-multiline": "error",       // https://eslint.org/docs/rules/no-unexpected-multiline
                "no-unsafe-finally": "error",             // https://eslint.org/docs/rules/no-unsafe-finally
                "no-unsafe-optional-chaining": "error",   // https://eslint.org/docs/rules/no-unsafe-optional-chaining
                "no-unused-labels": "error",              // https://eslint.org/docs/rules/no-unused-labels
                "no-useless-backreference": "error",      // https://eslint.org/docs/rules/no-useless-backreference
                "no-useless-catch": "error",              // https://eslint.org/docs/rules/no-useless-catch
                "no-useless-escape": "error",             // https://eslint.org/docs/rules/no-useless-escape
                "no-with": "error",                       // https://eslint.org/docs/rules/no-with
                "require-yield": "error",                 // https://eslint.org/docs/rules/require-yield
                "use-isnan": "error",                     // https://eslint.org/docs/rules/use-isnan

                // Other rules
                "default-param-last": "warn",             // https://eslint.org/docs/rules/default-param-last
                "eqeqeq": "warn",                         // https://eslint.org/docs/rules/eqeqeq

                // prettier plugin recommended settings
                // We explicitly set prettier options to prettier defaults, apart from tabWidth and endOfLine which are set to not conflict with
                // the Visual Studio defaults.  If we use prettier's defaults for these two rules then it fights with (default) Visual Studio.
                // All options are described on https://prettier.io/docs/en/options.html
                "prettier/prettier": ["warn", {
                    "tabWidth": 4,
                    "endOfLine": "crlf",
                    "printWidth": 80,
                    "semi": true,
                    "singleQuote": false,
                    "quoteProps": "as-needed",
                    "jsxSingleQuote": false,
                    "trailingComma": "es5",
                    "bracketSpacing": true,
                    "arrowParens": "always",
                }],
            }, // rules
        },
        {
            // JavaScript-only rules
            "files": ["*.js", "*.jsx", "*.mjs", "*.cjs"],
            "rules": {
                // Additional recommended rules, plus why they don't apply to TypeScript (ts)
                "constructor-super": "error",             // https://eslint.org/docs/rules/constructor-super ts(2335) & ts(2377)
                "getter-return": "error",                 // https://eslint.org/docs/rules/getter-return ts(2378)
                "no-const-assign": "error",               // https://eslint.org/docs/rules/no-const-assign ts(2588)
                "no-dupe-args": "error",                  // https://eslint.org/docs/rules/no-dupe-args ts(2300)
                "no-dupe-class-members": "error",         // https://eslint.org/docs/rules/no-dupe-class-members ts(2393) & ts(2300)
                "no-dupe-keys": "error",                  // https://eslint.org/docs/rules/no-dupe-keys ts(1117)
                "no-extra-semi": "error",                 // https://eslint.org/docs/rules/no-extra-semi ts rule used
                "no-func-assign": "error",                // https://eslint.org/docs/rules/no-func-assign ts(2539)
                "no-import-assign": "error",              // https://eslint.org/docs/rules/no-import-assign ts(2539) & ts(2540)
                "no-loss-of-precision": "error",          // https://eslint.org/docs/rules/no-loss-of-precision
                "no-new-symbol": "error",                 // https://eslint.org/docs/rules/no-new-symbol ts(2588)
                "no-obj-calls": "error",                  // https://eslint.org/docs/rules/no-obj-calls ts(2349)
                "no-redeclare": "error",                  // https://eslint.org/docs/rules/no-redeclare ts(2451)
                "no-setter-return": "error",              // https://eslint.org/docs/rules/no-setter-return ts(2408)
                "no-this-before-super": "error",          // https://eslint.org/docs/rules/no-this-before-super ts(2376)
                "no-undef": "error",                      // https://eslint.org/docs/rules/no-undef ts(2304)
                "no-unreachable": "error",                // https://eslint.org/docs/rules/no-unreachable ts(7027)
                "no-unsafe-negation": "error",            // https://eslint.org/docs/rules/no-unsafe-negation ts(2365) & ts(2360) & ts(2358)
                "no-unused-vars": "error",                // https://eslint.org/docs/rules/no-unused-vars ts rule used
                "valid-typeof": "error",                  // https://eslint.org/docs/rules/valid-typeof ts(2367)
            },  // rules
        },
        {
            // TypeScript-only rules
            "files": ["*.ts", "*.tsx"],
            "rules": {
                // For TypeScript files we follow typescript-eslint's recommendations re ESLint recommended rules: rules that are recommended to be
                // disabled are not applied to TypeScript (they are in the JavaScript only section above), additional recommended rules are enabled below
                // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/src/configs/eslint-recommended.ts
                "no-var": "error", // ts transpiles let/const to var, so no need for vars any more
                "prefer-const": "error", // ts provides better types with const
                "prefer-rest-params": "error", // ts provides better types with rest args over arguments
                "prefer-spread": "error", // ts transpiles spread to apply, so no need for manual apply

                // TypeScript-specific recommended rules from the typescript-eslint plugin
                // https://github.com/typescript-eslint/typescript-eslint/tree/master/packages/eslint-plugin#supported-rules
                // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/src/configs/recommended.ts
                "@typescript-eslint/adjacent-overload-signatures": "error",        // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/adjacent-overload-signatures.md
                "@typescript-eslint/ban-ts-comment": "error",                      // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/ban-ts-comment.md
                "@typescript-eslint/ban-types": "error",                           // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/ban-types.md
                "@typescript-eslint/no-array-constructor": "error",                // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-array-constructor.md
                "@typescript-eslint/no-empty-function": "error",                   // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-empty-function.md
                "@typescript-eslint/no-empty-interface": "error",                  // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-empty-interface.md
                "@typescript-eslint/no-explicit-any": "warn",                      // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-explicit-any.md
                "@typescript-eslint/no-extra-non-null-assertion": "error",         // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-extra-non-null-assertion.md
                "@typescript-eslint/no-extra-semi": "error",                       // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-extra-semi.md
                "@typescript-eslint/no-inferrable-types": "error",                 // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-inferrable-types.md
                "@typescript-eslint/no-loss-of-precision": "error",                // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-loss-of-precision.md
                "@typescript-eslint/no-misused-new": "error",                      // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-misused-new.md
                "@typescript-eslint/no-namespace": "error",                        // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-namespace.md
                "@typescript-eslint/no-non-null-asserted-optional-chain": "error", // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-non-null-asserted-optional-chain.md
                "@typescript-eslint/no-non-null-assertion": "warn",                // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-non-null-assertion.md
                "@typescript-eslint/no-this-alias": "error",                       // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-this-alias.md
                "@typescript-eslint/no-unnecessary-type-constraint": "error",      // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unnecessary-type-constraint.md
                "@typescript-eslint/no-unused-vars": "warn",                       // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unused-vars.md
                "@typescript-eslint/no-var-requires": "error",                     // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-var-requires.md
                "@typescript-eslint/prefer-as-const": "error",                     // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-as-const.md
                "@typescript-eslint/prefer-namespace-keyword": "error",            // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-namespace-keyword.md
                "@typescript-eslint/triple-slash-reference": "error",              // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/triple-slash-reference.md

                // TypeScript-specific recommended rules from the typescript-eslint plugin that need type information: for these
                // to work we need a tsconfig.json that includes the files we want linted, and to turn it on by setting
                // Tools/Options/TypeScript/Lint with tsconfig.json files to true.
                // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/src/configs/recommended-requiring-type-checking.ts
                //"@typescript-eslint/await-thenable": "error",                 // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/await-thenable.md
                //"@typescript-eslint/no-floating-promises": "error",           // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-floating-promises.md
                //"@typescript-eslint/no-for-in-array": "error",                // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-for-in-array.md
                //"@typescript-eslint/no-implied-eval'": "error",               // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-implied-eval.md
                //"@typescript-eslint/no-misused-promises": "error",            // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-misused-promises.md
                //"@typescript-eslint/no-unnecessary-type-assertion": "error",  // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unnecessary-type-assertion.md
                //"@typescript-eslint/no-unsafe-argument": "error",             // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-unsafe-argument.md
                //"@typescript-eslint/no-unsafe-assignment": "error",           // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-unsafe-assignment.md
                //"@typescript-eslint/no-unsafe-call": "error",                 // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-unsafe-call.md
                //"@typescript-eslint/no-unsafe-member-access": "error",        // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-unsafe-member-access.md
                //"@typescript-eslint/no-unsafe-return": "error",               // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/no-unsafe-return.md
                //"@typescript-eslint/require-await": "error",                  // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/require-await.md
                //"@typescript-eslint/restrict-plus-operands": "error",         // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/restrict-plus-operands.md
                //"@typescript-eslint/restrict-template-expressions": "error",  // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/restrict-template-expressions.md
                //"@typescript-eslint/unbound-method": "error",                 // https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/unbound-method.md
            },  // rules
        },
        {
            "files": ["*.md"],
            "plugins": ["md"],
            "parser": "markdown-eslint-parser",
            "rules": {
                "md/remark": [
                    "warn",
                    {
                        "plugins": [
                            "preset-lint-markdown-style-guide",
                            "frontmatter",
                            ["lint-maximum-line-length", false],    // Too painful, and Mads' extension wraps as you type
                            ["lint-maximum-heading-length", false], // Still too painful
                            ["lint-no-duplicate-headings", false],  // Perfectly valid 'Background' subheadings get flagged
                            ["lint-ordered-list-marker-value", [1, "ordered"]],  // Let's see the actual numbers
                            ["lint-no-shortcut-reference-link", false],   // Giving false positives
                            ["lint-no-emphasis-as-heading", false]   // Giving false positives
                        ],
                    },
                ],
            },
        },
    ],
};

const prettierDisabledConfig = {
    "overrides": [
        {
            "files": ["*.js", "*.jsx", "*.mjs", "*.cjs", "*.ts", "*.tsx"],
            "rules": {
                // Turn off Prettier's one rule
                "prettier/prettier": "off",
                // Enable appropriate ESLint rules, give them similar behavior to Prettier
                "arrow-parens": "warn",             // https://eslint.org/docs/rules/arrow-parens
                "eol-last": "warn",                 // https://eslint.org/docs/rules/eol-last
                "new-parens": "warn",               // https://eslint.org/docs/rules/new-parens
                "no-multiple-empty-lines": "warn",  // https://eslint.org/docs/rules/no-multiple-empty-lines
                "no-trailing-spaces": "warn",       // https://eslint.org/docs/rules/no-trailing-spaces
            },
        },
        {
            "files": ["*.js", "*.jsx", "*.mjs", "*.cjs"],
            "rules": {
                "comma-dangle": ["warn", "always-multiline"],                 // https://eslint.org/docs/rules/comma-dangle
                "indent": "warn",                                             // https://eslint.org/docs/rules/indent
                "quotes": ["warn", "double",
                    { "avoidEscape": true, "allowTemplateLiterals": true }],  // https://eslint.org/docs/rules/quotes
                "semi": "warn",                                               // https://eslint.org/docs/rules/semi
            },
        },
        {
            "files": ["*.ts", "*.tsx"],
            "rules": {
                "@typescript-eslint/comma-dangle": ["warn", "always-multiline"], // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/comma-dangle.md
                // The indent rule comes with a warning from its author but seems to work OK usually https://github.com/typescript-eslint/typescript-eslint/issues/1824
                "@typescript-eslint/indent": "warn",                             // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/indent.md
                "@typescript-eslint/member-delimiter-style": "warn",             // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/member-delimiter-style.md
                "@typescript-eslint/quotes": ["warn", "double",
                    { "avoidEscape": true, "allowTemplateLiterals": true }],     // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/quotes.md
                "@typescript-eslint/semi": "warn",                               // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/semi.md
                "@typescript-eslint/type-annotation-spacing": "warn",            // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/type-annotation-spacing.md
            },
        },
    ],
};

if (!prettierEnabled) {
    config.overrides[0].plugins.splice(1, 1); // Remove element at index 1 (="prettier")
    config.overrides[0].rules = Object.assign(config.overrides[0].rules, prettierDisabledConfig.overrides[0].rules);
    config.overrides[1].rules = Object.assign(config.overrides[1].rules, prettierDisabledConfig.overrides[1].rules);
    config.overrides[2].rules = Object.assign(config.overrides[2].rules, prettierDisabledConfig.overrides[2].rules);
}

module.exports = config;