Fixes #3787 -- ESLint updates and linting cleanup (#3790)

* ESLint updates and linting cleanup

* Exclude test files from some linting rules for now

* Fix some TypeScript and build issues

packages/less/.eslintrc.js

@@ -0,0 +1,63 @@
+module.exports = {
+    'parser': '@typescript-eslint/parser',
+    'extends': 'eslint:recommended',
+    'parserOptions': {
+        'ecmaVersion': 2018,
+        'sourceType': 'module'
+    },
+    'plugins': ['@typescript-eslint'],
+    'env': {
+        'browser': true,
+        'node': true,
+        'mocha': true
+    },
+    'globals': {},
+    'rules': {
+        indent: ['error', 4, {
+            SwitchCase: 1
+        }],
+        'no-empty': ['error', { 'allowEmptyCatch': true }],
+        quotes: ['error', 'single', {
+            avoidEscape: true
+        }],
+        /**
+         * The codebase uses some while(true) statements.
+         * Refactor to remove this rule.
+         */
+        'no-constant-condition': 0,
+        /**
+         * Less combines assignments with conditionals sometimes
+         */
+        'no-cond-assign': 0,
+        /**
+         * @todo - remove when some kind of code style (XO?) is added
+         */
+        'no-multiple-empty-lines': 'error'
+    },
+    'overrides': [
+        {
+            files: ['*.ts'],
+            extends: ['plugin:@typescript-eslint/recommended'],
+            rules: {
+                /**
+                 * Suppress until Less has better-defined types
+                 * @see https://github.com/less/less.js/discussions/3786
+                 */
+                '@typescript-eslint/no-explicit-any': 0
+            }
+        },
+        {
+            files: ['test/**/*.{js,ts}', 'benchmark/index.js'],
+            /**
+             * @todo - fix later
+             */
+            rules: {
+                'no-undef': 0,
+                'no-useless-escape': 0,
+                'no-unused-vars': 0,
+                'no-redeclare': 0,
+                '@typescript-eslint/no-unused-vars': 0
+            }
+        },
+    ]
+}

packages/less/.eslintrc.json

@@ -1,71 +0,0 @@
-{
-    "parser": "@typescript-eslint/parser",
-    "parserOptions": {
-        "ecmaVersion": 2018,
-        "sourceType": "module"
-    },
-    "plugins": ["@typescript-eslint"],
-    "env": {
-        "browser": true,
-        "node": true
-    },
-    "globals": {},
-    "rules": {
-        "no-eval": 2,
-        "no-use-before-define": [
-            2,
-            {
-                "functions": false
-            }
-        ],
-        "no-undef": 0,
-        "no-unused-vars": 1,
-        "no-caller": 2,
-        "no-eq-null": 1,
-        "guard-for-in": 2,
-        "no-implicit-coercion": [
-            2,
-            {
-                "boolean": false,
-                "string": true,
-                "number": true
-            }
-        ],
-        "no-with": 2,
-        "no-mixed-spaces-and-tabs": 2,
-        "no-multiple-empty-lines": 2,
-        "dot-location": [2, "property"],
-        "operator-linebreak": [0, "after"],
-        "keyword-spacing": [2, {}],
-        "space-unary-ops": [
-            2,
-            {
-                "words": false,
-                "nonwords": false
-            }
-        ],
-        "no-spaced-func": 2,
-        "space-before-function-paren": [
-            1,
-            {
-                "anonymous": "ignore",
-                "named": "never"
-            }
-        ],
-        "comma-dangle": [2, "never"],
-        "no-trailing-spaces": 0,
-        "max-len": [2, 160],
-        "comma-style": [2, "last"],
-        "curly": [2, "all"],
-        "space-infix-ops": 2,
-        "spaced-comment": 1,
-        "space-before-blocks": [2, "always"],
-        "indent": [
-            2,
-            4,
-            {
-                "SwitchCase": 1
-            }
-        ]
-    }
-}

packages/less/Gruntfile.js

@@ -283,7 +283,7 @@ module.exports = function(grunt) {
                 "!test/less/errors/plugin/plugin-error.js"
             ],
             options: {
-                configFile: ".eslintrc.json",
+                configFile: ".eslintrc.js",
                 fix: true
             }
         },

packages/less/benchmark/index.js

@@ -1,6 +1,6 @@
 var path = require('path'),
     fs = require('fs'),
-    now = require("performance-now");
+    now = require('performance-now');
 
 var less = require('../.');
 var file = path.join(__dirname, 'benchmark.less');
@@ -10,12 +10,12 @@ if (process.argv[2]) { file = path.join(process.cwd(), process.argv[2]) }
 fs.readFile(file, 'utf8', function (e, data) {
     var start, total;
 
-    console.log("Benchmarking...\n", path.basename(file) + " (" +
+    console.log('Benchmarking...\n', path.basename(file) + ' (' +
-             parseInt(data.length / 1024) + " KB)", "");
+             parseInt(data.length / 1024) + ' KB)', '');
 
     var renderBenchmark = []
-      , parserBenchmark = []
+        , parserBenchmark = []
-      , evalBenchmark = [];
+        , evalBenchmark = [];
 
     var totalruns = 30;
     var ignoreruns = 5;
@@ -74,13 +74,13 @@ fs.readFile(file, 'utf8', function (e, data) {
             var variation = maxtime - mintime;
             var variationperc = (variation / avgtime) * 100;
 
-            console.log("Min. Time: " + Math.round(mintime) + " ms");
+            console.log('Min. Time: ' + Math.round(mintime) + ' ms');
-            console.log("Max. Time: " + Math.round(maxtime) + " ms");
+            console.log('Max. Time: ' + Math.round(maxtime) + ' ms');
-            console.log("Total Average Time: " + Math.round(avgtime) + " ms (" +
+            console.log('Total Average Time: ' + Math.round(avgtime) + ' ms (' +
                 parseInt(1000 / avgtime *
-                data.length / 1024) + " KB\/s)");
+                data.length / 1024) + ' KB\/s)');
-            console.log("+/- " + Math.round(variationperc) + "%");
+            console.log('+/- ' + Math.round(variationperc) + '%');
-            console.log("");
+            console.log('');
         }
        
         analyze('Parsing', parserBenchmark);

packages/less/build/rollup.js

@@ -47,7 +47,7 @@ async function buildBrowser() {
                 include: [/^.+\.min\.js$/],
                 output: {
                     comments: function(node, comment) {
-                        if (comment.type == "comment2") {
+                        if (comment.type == 'comment2') {
                             // preserve banner
                             return /@license/i.test(comment.value);
                         }

packages/less/package.json

@@ -37,11 +37,13 @@
 	"scripts": {
 		"test": "grunt test",
 		"grunt": "grunt",
+		"lint": "eslint '**/*.{ts,js}'",
+		"lint:fix": "eslint '**/*.{ts,js}' --fix",
 		"build": "npm-run-all clean compile",
 		"clean": "shx rm -rf ./lib tsconfig.tsbuildinfo",
-		"compile": "tsc -p tsconfig.json",
+		"compile": "tsc -p tsconfig.build.json",
 		"copy:root": "shx cp -rf ./dist ../../",
-		"dev": "tsc -p tsconfig.json -w",
+		"dev": "tsc -p tsconfig.build.json -w",
 		"prepublishOnly": "grunt dist"
 	},
 	"optionalDependencies": {

packages/less/src/less-browser/bootstrap.js

@@ -3,8 +3,6 @@
  * used in the browser distributed version of less
  * to kick-start less using the browser api
  */
-/* global window, document */
-
 import defaultOptions from '../less/default-options';
 import addDefaultOptions from './add-default-options';
 import root from './index';
@@ -13,7 +11,7 @@ const options = defaultOptions();
 
 if (window.less) {
     for (const key in window.less) {
-        if (window.less.hasOwnProperty(key)) {
+        if (Object.prototype.hasOwnProperty.call(window.less, key)) {
             options[key] = window.less[key];
         }
     }

packages/less/src/less-browser/cache.js

@@ -29,7 +29,7 @@ export default (window, options, logger) => {
             let vars      = cache && cache.getItem(`${path}:vars`);
 
             modifyVars = modifyVars || {};
-            vars = vars || "{}"; // if not set, treat as the JSON representation of an empty object
+            vars = vars || '{}'; // if not set, treat as the JSON representation of an empty object
 
             if (timestamp && webInfo.lastModified &&
                 (new Date(webInfo.lastModified).valueOf() ===

packages/less/src/less-browser/error-reporting.js

@@ -11,7 +11,7 @@ export default (window, less, options) => {
         let content;
         const errors = [];
         const filename = e.filename || rootHref;
-        const filenameNoPath = filename.match(/([^\/]+(\?.*)?)$/)[1];
+        const filenameNoPath = filename.match(/([^/]+(\?.*)?)$/)[1];
 
         elem.id        = id;
         elem.className = 'less-error-message';
@@ -113,7 +113,7 @@ export default (window, less, options) => {
         }
     }
 
-    function removeErrorConsole(path) {
+    function removeErrorConsole() {
         // no action
     }
 

packages/less/src/less-browser/file-manager.js

@@ -1,5 +1,3 @@
-/* global window, XMLHttpRequest */
-
 import AbstractFileManager from '../less/environment/abstract-file-manager.js';
 
 let options;
@@ -66,7 +64,7 @@ FileManager.prototype = Object.assign(new AbstractFileManager(), {
         fileCache = {};
     },
 
-    loadFile(filename, currentDirectory, options, environment) {
+    loadFile(filename, currentDirectory, options) {
         // TODO: Add prefix support like less-node?
         // What about multiple paths?
 

packages/less/src/less-browser/index.js

@@ -39,7 +39,7 @@ export default (window, options) => {
     function clone(obj) {
         const cloned = {};
         for (const prop in obj) {
-            if (obj.hasOwnProperty(prop)) {
+            if (Object.prototype.hasOwnProperty.call(obj, prop)) {
                 cloned[prop] = obj[prop];
             }
         }
@@ -159,6 +159,10 @@ export default (window, options) => {
             less.watchTimer = setInterval(() => {
                 if (less.watchMode) {
                     fileManager.clearFileCache();
+                    /**
+                     * @todo remove when this is typed with JSDoc
+                     */
+                    // eslint-disable-next-line no-unused-vars
                     loadStyleSheets((e, css, _, sheet, webInfo) => {
                         if (e) {
                             errors.add(e, e.href || sheet.href);
@@ -174,7 +178,7 @@ export default (window, options) => {
     //
     // Watch mode
     //
-    less.watch   = function () {
+    less.watch = function () {
         if (!less.watchMode ) {
             less.env = 'development';
             initRunningMode();
@@ -205,7 +209,7 @@ export default (window, options) => {
     // Asynchronously get all <link> tags with the 'rel' attribute set to
     // "stylesheet/less", returning a Promise.
     //
-    less.registerStylesheets = () => new Promise((resolve, reject) => {
+    less.registerStylesheets = () => new Promise((resolve) => {
         less.registerStylesheetsImmediately();
         resolve();
     });

packages/less/src/less-browser/plugin-loader.js

@@ -1,6 +1,6 @@
-// TODO: Add tests for browser @plugin
+/**
-/* global window */
+ * @todo Add tests for browser `@plugin`
-
+ */
 import AbstractPluginLoader from '../less/environment/abstract-plugin-loader.js';
 
 /**

packages/less/src/less-browser/utils.js

@@ -1,17 +1,17 @@
 
 export function extractId(href) {
-    return href.replace(/^[a-z-]+:\/+?[^\/]+/, '')  // Remove protocol & domain
+    return href.replace(/^[a-z-]+:\/+?[^/]+/, '')  // Remove protocol & domain
-        .replace(/[\?\&]livereload=\w+/, '')        // Remove LiveReload cachebuster
+        .replace(/[?&]livereload=\w+/, '')        // Remove LiveReload cachebuster
         .replace(/^\//, '')                         // Remove root /
         .replace(/\.[a-zA-Z]+$/, '')                // Remove simple extension
-        .replace(/[^\.\w-]+/g, '-')                 // Replace illegal characters
+        .replace(/[^.\w-]+/g, '-')                 // Replace illegal characters
         .replace(/\./g, ':');                       // Replace dots with colons(for valid id)
 }
 
 export function addDataAttr(options, tag) {
     if (!tag) {return;} // in case of tag is null or undefined
     for (const opt in tag.dataset) {
-        if (tag.dataset.hasOwnProperty(opt)) {
+        if (Object.prototype.hasOwnProperty.call(tag.dataset, opt)) {
             if (opt === 'env' || opt === 'dumpLineNumbers' || opt === 'rootpath' || opt === 'errorReporting') {
                 options[opt] = tag.dataset[opt];
             } else {

packages/less/src/less-node/file-manager.js

@@ -61,6 +61,23 @@ FileManager.prototype = Object.assign(new AbstractFileManager(), {
 
         function getFileData(fulfill, reject) {
             (function tryPathIndex(i) {
+                function tryWithExtension() {
+                    const extFilename = options.ext ? self.tryAppendExtension(fullFilename, options.ext) : fullFilename;
+
+                    if (extFilename !== fullFilename && !explicit && paths[i] === '.') {
+                        try {
+                            fullFilename = require.resolve(extFilename);
+                            isNodeModule = true;
+                        }
+                        catch (e) {
+                            filenamesTried.push(npmPrefix + extFilename);
+                            fullFilename = extFilename;
+                        }
+                    }
+                    else {
+                        fullFilename = extFilename;
+                    }
+                }
                 if (i < paths.length) {
                     (function tryPrefix(j) {
                         if (j < prefixes.length) {
@@ -83,25 +100,7 @@ FileManager.prototype = Object.assign(new AbstractFileManager(), {
                             }
                             else {
                                 tryWithExtension();
-                            }
+                            }                            
-
-                            function tryWithExtension() {
-                                const extFilename = options.ext ? self.tryAppendExtension(fullFilename, options.ext) : fullFilename;
-
-                                if (extFilename !== fullFilename && !explicit && paths[i] === '.') {
-                                    try {
-                                        fullFilename = require.resolve(extFilename);
-                                        isNodeModule = true;
-                                    }
-                                    catch (e) {
-                                        filenamesTried.push(npmPrefix + extFilename);
-                                        fullFilename = extFilename;
-                                    }
-                                }
-                                else {
-                                    fullFilename = extFilename;
-                                }
-                            }
 
                             const readFileArgs = [fullFilename];
                             if (!options.rawBuffer) {

packages/less/src/less-node/lessc-helper.js

@@ -88,4 +88,5 @@ const lessc_helper = {
 };
 
 // Exports helper functions
+// eslint-disable-next-line no-prototype-builtins
 for (const h in lessc_helper) { if (lessc_helper.hasOwnProperty(h)) { exports[h] = lessc_helper[h]; }}

packages/less/src/less-node/url-file-manager.js

@@ -1,3 +1,8 @@
+/* eslint-disable no-unused-vars */
+/**
+ * @todo - remove top eslint rule when FileManagers have JSDoc type
+ * and are TS-type-checked
+ */
 const isUrlRe = /^(?:https?:)?\/\//i;
 import url from 'url';
 let request;

packages/less/src/less/contexts.js

@@ -6,7 +6,7 @@ const copyFromOriginal = function copyFromOriginal(original, destination, proper
     if (!original) { return; }
 
     for (let i = 0; i < propertiesToCopy.length; i++) {
-        if (original.hasOwnProperty(propertiesToCopy[i])) {
+        if (Object.prototype.hasOwnProperty.call(original, propertiesToCopy[i])) {
             destination[propertiesToCopy[i]] = original[propertiesToCopy[i]];
         }
     }
@@ -113,7 +113,7 @@ contexts.Eval.prototype.pathRequiresRewrite = function (path) {
 contexts.Eval.prototype.rewritePath = function (path, rootpath) {
     let newPath;
 
-    rootpath = rootpath || '';
+    rootpath = rootpath || '';
     newPath = this.normalizePath(rootpath + path);
 
     // If a path was explicit relative and the rootpath was not an absolute path

packages/less/src/less/default-options.js

@@ -67,4 +67,4 @@ export default function() {
         /* This option allows you to specify a argument to go on to every URL.  */
         urlArgs: ''
     }
-};
+}

packages/less/src/less/environment/abstract-file-manager.js

@@ -15,7 +15,7 @@ class AbstractFileManager {
     }
 
     tryAppendExtension(path, ext) {
-        return /(\.[a-z]*$)|([\?;].*)$/.test(path) ? path : path + ext;
+        return /(\.[a-z]*$)|([?;].*)$/.test(path) ? path : path + ext;
     }
 
     tryAppendLessExtension(path) {
@@ -71,7 +71,13 @@ class AbstractFileManager {
         return diff;
     }
 
-    // helper function, not part of API
+    /**
+     * Helper function, not part of API.
+     * This should be replaceable by newer Node / Browser APIs
+     * 
+     * @param {string} url 
+     * @param {string} baseUrl
+     */
     extractUrlParts(url, baseUrl) {
         // urlParts[1] = protocol://hostname/ OR /
         // urlParts[2] = / if path relative to host base
@@ -79,7 +85,7 @@ class AbstractFileManager {
         // urlParts[4] = filename
         // urlParts[5] = parameters
 
-        const urlPartsRegex = /^((?:[a-z-]+:)?\/{2}(?:[^\/\?#]*\/)|([\/\\]))?((?:[^\/\\\?#]*[\/\\])*)([^\/\\\?#]*)([#\?].*)?$/i;
+        const urlPartsRegex = /^((?:[a-z-]+:)?\/{2}(?:[^/?#]*\/)|([/\\]))?((?:[^/\\?#]*[/\\])*)([^/\\?#]*)([#?].*)?$/i;
 
         const urlParts = url.match(urlPartsRegex);
         const returner = {};

packages/less/src/less/environment/environment-api.js

@@ -1,25 +0,0 @@
-export default {
-    /**
-     * Converts a string to a base 64 string
-     * @param str
-     */
-    encodeBase64: function(str) {
-    },
-    /**
-     * Lookup the mime-type of a filename
-     * @param filename
-     */
-    mimeLookup: function (filename) {
-    },
-    /**
-     * Look up the charset of a mime type
-     * @param mime
-     */
-    charsetLookup: function (mime) {
-    },
-    /**
-     * Gets a source map generator
-     */
-    getSourceMapGenerator: function getSourceMapGenerator() {
-    }
-};

packages/less/src/less/environment/environment-api.ts

@@ -0,0 +1,21 @@
+export interface Environment {
+    /**
+     * Converts a string to a base 64 string
+     */
+    encodeBase64(str: string): string
+    /**
+     * Lookup the mime-type of a filename
+     */
+    mimeLookup(filename: string): string
+    /**
+     * Look up the charset of a mime type
+     * @param mime
+     */
+    charsetLookup(mime: string): string
+    /**
+     * Gets a source map generator
+     *
+     * @todo - Figure out precise type
+     */
+    getSourceMapGenerator(): any
+}

packages/less/src/less/environment/file-manager-api.js

@@ -1,103 +0,0 @@
-export default {
-    /**
-     * Given the full path to a file, return the path component
-     * Provided by AbstractFileManager
-     * @param {string} filename
-     * @returns {string}
-     */
-    getPath: function(filename) {
-    },
-    /**
-     * Append a .less extension if appropriate. Only called if less thinks one could be added.
-     * Provided by AbstractFileManager
-     * @param filename
-     * @returns {string}
-     */
-    tryAppendLessExtension: function(filename) {
-    },
-    /**
-     * Whether the rootpath should be converted to be absolute.
-     * The browser ovverides this to return true because urls must be absolute.
-     * Provided by AbstractFileManager (returns false)
-     * @returns {bool}
-     */
-    alwaysMakePathsAbsolute: function() {
-    },
-    /**
-     * Returns whether a path is absolute
-     * Provided by AbstractFileManager
-     * @param {string} path
-     * @returns {bool}
-     */
-    isPathAbsolute: function(path) {
-    },
-    /**
-     * joins together 2 paths
-     * Provided by AbstractFileManager
-     * @param {string} basePath
-     * @param {string} laterPath
-     */
-    join: function(basePath, laterPath) {
-    },
-    /**
-     * Returns the difference between 2 paths
-     * E.g. url = a/ baseUrl = a/b/ returns ../
-     * url = a/b/ baseUrl = a/ returns b/
-     * Provided by AbstractFileManager
-     * @param {string} url
-     * @param {string} baseUrl
-     * @returns {string}
-     */
-    pathDiff: function(url, baseUrl) {
-    },
-    /**
-     * Returns whether this file manager supports this file for syncronous file retrieval
-     * If true is returned, loadFileSync will then be called with the file.
-     * Provided by AbstractFileManager (returns false)
-     * @param {string} filename
-     * @param {string} currentDirectory
-     * @param {object} options
-     * @param {less.environment.environment} environment
-     * @returns {bool}
-     */
-    supportsSync: function(filename, currentDirectory, options, environment) {
-    },
-    /**
-     *
-     * @param {string} filename
-     * @param {string} currentDirectory
-     * @param {object} options
-     * @param {less.environment.environment} environment
-     * @returns {bool}
-     */
-    supports: function(filename, currentDirectory, options, environment) {
-    },
-    /**
-     * Loads a file asynchronously. Expects a promise that either rejects with an error or fulfills with an
-     * object containing
-     *  { filename: - full resolved path to file
-     *    contents: - the contents of the file, as a string }
-     *
-     * @param {string} filename
-     * @param {string} currentDirectory
-     * @param {object} options
-     * @param {less.environment.environment} environment
-     * @returns {Promise}
-     */
-    loadFile: function(filename, currentDirectory, options, environment) {
-    },
-    /**
-     * Loads a file synchronously. Expects an immediate return with an object containing
-     *  { error: - error object if an error occurs
-     *    filename: - full resolved path to file
-     *    contents: - the contents of the file, as a string }
-     *
-     * @param {string} filename
-     * @param {string} currentDirectory
-     * @param {object} options
-     * @param {less.environment.environment} environment
-     * @returns {object} should be an object containing error or contents and filename
-     */
-    loadFileSync: function(filename, currentDirectory, options, environment) {
-    }
-};

packages/less/src/less/environment/file-manager-api.ts

@@ -0,0 +1,77 @@
+import type { Environment } from './environment-api'
+
+export interface FileManager {
+    /**
+     * Given the full path to a file, return the path component
+     * Provided by AbstractFileManager
+     */
+    getPath(filename: string): string
+    /**
+     * Append a .less extension if appropriate. Only called if less thinks one could be added.
+     * Provided by AbstractFileManager
+     */
+    tryAppendLessExtension(filename: string): string
+    /**
+     * Whether the rootpath should be converted to be absolute.
+     * The browser ovverides this to return true because urls must be absolute.
+     * Provided by AbstractFileManager (returns false)
+     */
+    alwaysMakePathsAbsolute(): boolean
+    /**
+     * Returns whether a path is absolute
+     * Provided by AbstractFileManager
+     */
+    isPathAbsolute(path: string): boolean
+    /**
+     * joins together 2 paths
+     * Provided by AbstractFileManager
+     */
+    join(basePath: string, laterPath: string): string
+    /**
+     * Returns the difference between 2 paths
+     * E.g. url = a/ baseUrl = a/b/ returns ../
+     * url = a/b/ baseUrl = a/ returns b/
+     * Provided by AbstractFileManager
+     */
+    pathDiff(url: string, baseUrl: string): string
+    /**
+     * Returns whether this file manager supports this file for syncronous file retrieval
+     * If true is returned, loadFileSync will then be called with the file.
+     * Provided by AbstractFileManager (returns false)
+     * 
+     * @todo - Narrow Options type
+     */
+    supportsSync(
+        filename: string,
+        currentDirectory: string,
+        options: Record<string, any>,
+        environment: Environment
+    ): boolean
+    /**
+     * If file manager supports async file retrieval for this file type
+     */
+    supports(
+        filename: string,
+        currentDirectory: string,
+        options: Record<string, any>,
+        environment: Environment
+    ): boolean
+    /**
+     * Loads a file asynchronously.
+     */
+    loadFile(
+        filename: string,
+        currentDirectory: string,
+        options: Record<string, any>,
+        environment: Environment
+    ): Promise<{ filename: string, contents: string }>
+    /**
+     * Loads a file synchronously. Expects an immediate return with an object
+     */
+    loadFileSync(
+        filename: string,
+        currentDirectory: string,
+        options: Record<string, any>,
+        environment: Environment
+    ): { error?: unknown, filename: string, contents: string }
+}

packages/less/src/less/functions/color-blending.js

@@ -76,6 +76,7 @@ const colorBlendModeFunctions = {
 };
 
 for (const f in colorBlendModeFunctions) {
+    // eslint-disable-next-line no-prototype-builtins
     if (colorBlendModeFunctions.hasOwnProperty(f)) {
         colorBlend[f] = colorBlend.bind(null, colorBlendModeFunctions[f]);
     }

packages/less/src/less/functions/color.js

@@ -121,6 +121,25 @@ colorFunctions = {
         }
     },
     hsla: function (h, s, l, a) {
+        let m1;
+        let m2;
+
+        function hue(h) {
+            h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
+            if (h * 6 < 1) {
+                return m1 + (m2 - m1) * h * 6;
+            }
+            else if (h * 2 < 1) {
+                return m2;
+            }
+            else if (h * 3 < 2) {
+                return m1 + (m2 - m1) * (2 / 3 - h) * 6;
+            }
+            else {
+                return m1;
+            }
+        }
+
         try {
             if (h instanceof Color) {
                 if (s) {
@@ -131,25 +150,6 @@ colorFunctions = {
                 return new Color(h.rgb, a, 'hsla');
             }
 
-            let m1;
-            let m2;
-
-            function hue(h) {
-                h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
-                if (h * 6 < 1) {
-                    return m1 + (m2 - m1) * h * 6;
-                }
-                else if (h * 2 < 1) {
-                    return m2;
-                }
-                else if (h * 3 < 2) {
-                    return m1 + (m2 - m1) * (2 / 3 - h) * 6;
-                }
-                else {
-                    return m1;
-                }
-            }
-
             h = (number(h) % 360) / 360;
             s = clamp(number(s));l = clamp(number(l));a = clamp(number(a));
 

packages/less/src/less/functions/function-registry.js

@@ -6,6 +6,7 @@ function makeRegistry( base ) {
             // the registry by function-caller uses lower case as well.
             name = name.toLowerCase();
 
+            // eslint-disable-next-line no-prototype-builtins
             if (this._data.hasOwnProperty(name)) {
                 // TODO warn
             }

packages/less/src/less/functions/list.js

@@ -142,14 +142,14 @@ export default {
                     false, false, this.index, this.currentFileInfo));
             }
 
-            rules.push(new Ruleset([ new(Selector)([ new Element("", '&') ]) ],
+            rules.push(new Ruleset([ new(Selector)([ new Element('', '&') ]) ],
                 newRules,
                 rs.strictImports,
                 rs.visibilityInfo()
             ));
         }
 
-        return new Ruleset([ new(Selector)([ new Element("", '&') ]) ],
+        return new Ruleset([ new(Selector)([ new Element('', '&') ]) ],
             rules,
             rs.strictImports,
             rs.visibilityInfo()

packages/less/src/less/functions/math.js

@@ -15,6 +15,7 @@ const mathFunctions = {
 };
 
 for (const f in mathFunctions) {
+    // eslint-disable-next-line no-prototype-builtins
     if (mathFunctions.hasOwnProperty(f)) {
         mathFunctions[f] = mathHelper.bind(null, Math[f], mathFunctions[f]);
     }

packages/less/src/less/functions/svg.js

@@ -4,7 +4,7 @@ import Expression from '../tree/expression';
 import Quoted from '../tree/quoted';
 import URL from '../tree/url';
 
-export default environment => {
+export default () => {
     return { 'svg-gradient': function(direction) {
         let stops;
         let gradientDirectionSvg;

packages/less/src/less/import-manager.js

@@ -180,4 +180,4 @@ export default function(environment) {
     }
 
     return ImportManager;
-};
+}

packages/less/src/less/index.js

@@ -95,4 +95,4 @@ export default function(environment, fileManagers) {
     initial.render = initial.render.bind(api);
 
     return api;
-};
+}

packages/less/src/less/less-error.js

@@ -62,8 +62,7 @@ const LessError = function(e, fileContentMap, currentFilename) {
                 func();
             } catch (e) {
                 const match = e.stack.match(anonymousFunc);
-                var line = parseInt(match[2]);
+                lineAdjust = 1 - parseInt(match[2]);
-                lineAdjust = 1 - line;
             }
 
             if (found) {

packages/less/src/less/parse-tree.js

@@ -54,7 +54,7 @@ export default function(SourceMapBuilder) {
 
             result.imports = [];
             for (const file in this.imports.files) {
-                if (this.imports.files.hasOwnProperty(file) && file !== this.imports.rootFilename) {
+                if (Object.prototype.hasOwnProperty.call(this.imports.files, file) && file !== this.imports.rootFilename) {
                     result.imports.push(file);
                 }
             }
@@ -63,4 +63,4 @@ export default function(SourceMapBuilder) {
     }
 
     return ParseTree;
-};
+}

packages/less/src/less/parse.js

@@ -39,7 +39,7 @@ export default function(environment, ParseTree, ImportManager) {
                 rootFileInfo = options.rootFileInfo;
             } else {
                 const filename = options.filename || 'input';
-                const entryPath = filename.replace(/[^\/\\]*$/, '');
+                const entryPath = filename.replace(/[^/\\]*$/, '');
                 rootFileInfo = {
                     filename,
                     rewriteUrls: context.rewriteUrls,
@@ -84,4 +84,4 @@ export default function(environment, ParseTree, ImportManager) {
         }
     };
     return parse;
-};
+}

packages/less/src/less/parser/chunker.js

@@ -119,4 +119,4 @@ export default function (input, fail) {
 
     emitChunk(true);
     return chunks;
-};
+}

packages/less/src/less/parser/parser-input.js

@@ -182,13 +182,14 @@ export default () => {
                 case '\r':
                 case '\n':
                     break;
-                case startChar:
+                case startChar: {
                     const str = input.substr(currentPosition, i + 1);
                     if (!loc && loc !== 0) {
                         skipWhitespace(i + 1);
                         return str
                     }
                     return [startChar, str];
+                }
                 default:
             }
         }
@@ -220,7 +221,6 @@ export default () => {
         }
 
         do {
-            let prevChar;
             let nextChar = input.charAt(i);
             if (blockDepth === 0 && testChar(nextChar)) {
                 returnVal = input.substr(lastPos, i - lastPos);
@@ -286,7 +286,7 @@ export default () => {
                         break;
                     case '}':
                     case ')':
-                    case ']':
+                    case ']': {
                         const expected = blockStack.pop();
                         if (nextChar === expected) {
                             blockDepth--;
@@ -296,13 +296,13 @@ export default () => {
                             returnVal = expected;
                             loop = false;
                         }
+                    }
                 }
                 i++;
                 if (i > length) {
                     loop = false;
                 }
             }
-            prevChar = nextChar;
         } while (loop);
 
         return returnVal ? returnVal : null;

packages/less/src/less/parser/parser.js

@@ -154,7 +154,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                         error('@plugin statements are not allowed when disablePluginRule is set to true');
                     }
                 }
-            };
+            }
 
             globalVars = (additionalData && additionalData.globalVars) ? `${Parser.serializeVars(additionalData.globalVars)}\n` : '';
             modifyVars = (additionalData && additionalData.modifyVars) ? `\n${Parser.serializeVars(additionalData.modifyVars)}` : '';
@@ -422,7 +422,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
 
                     parserInput.save();
 
-                    name = parserInput.$re(/^([\w-]+|%|~|progid:[\w\.]+)\(/);
+                    name = parserInput.$re(/^([\w-]+|%|~|progid:[\w.]+)\(/);
                     if (!name) {
                         parserInput.forget();
                         return;
@@ -576,7 +576,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     }
 
                     value = this.quoted() || this.variable() || this.property() ||
-                            parserInput.$re(/^(?:(?:\\[\(\)'"])|[^\(\)'"])+/) || '';
+                            parserInput.$re(/^(?:(?:\\[()'"])|[^()'"])+/) || '';
 
                     parserInput.autoCommentAbsorb = true;
 
@@ -661,7 +661,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     let rgb;
                     parserInput.save();
 
-                    if (parserInput.currentChar() === '#' && (rgb = parserInput.$re(/^#([A-Fa-f0-9]{8}|[A-Fa-f0-9]{6}|[A-Fa-f0-9]{3,4})([\w.#\[])?/))) {
+                    if (parserInput.currentChar() === '#' && (rgb = parserInput.$re(/^#([A-Fa-f0-9]{8}|[A-Fa-f0-9]{6}|[A-Fa-f0-9]{3,4})([\w.#[])?/))) {
                         if (!rgb[2]) {
                             parserInput.forget();
                             return new(tree.Color)(rgb[1], undefined, rgb[0]);
@@ -712,7 +712,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 unicodeDescriptor: function () {
                     let ud;
 
-                    ud = parserInput.$re(/^U\+[0-9a-fA-F?]+(\-[0-9a-fA-F?]+)?/);
+                    ud = parserInput.$re(/^U\+[0-9a-fA-F?]+(-[0-9a-fA-F?]+)?/);
                     if (ud) {
                         return new(tree.UnicodeDescriptor)(ud[0]);
                     }
@@ -1161,7 +1161,6 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
 
                 ruleLookups: function() {
                     let rule;
-                    let args;
                     const lookups = [];
 
                     if (parserInput.currentChar() !== '[') {
@@ -1170,7 +1169,6 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
 
                     while (true) {
                         parserInput.save();
-                        args = null;
                         rule = this.lookupValue();
                         if (!rule && rule !== '') {
                             parserInput.restore();
@@ -1268,9 +1266,10 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 c = this.combinator();
 
                 e = parserInput.$re(/^(?:\d+\.\d+|\d+)%/) ||
+                    // eslint-disable-next-line no-control-regex
                     parserInput.$re(/^(?:[.#]?|:*)(?:[\w-]|[^\x00-\x9f]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/) ||
                     parserInput.$char('*') || parserInput.$char('&') || this.attribute() ||
-                    parserInput.$re(/^\([^&()@]+\)/) ||  parserInput.$re(/^[\.#:](?=@)/) ||
+                    parserInput.$re(/^\([^&()@]+\)/) ||  parserInput.$re(/^[.#:](?=@)/) ||
                     this.entities.variableCurly();
 
                 if (!e) {
@@ -1389,11 +1388,11 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     }
                     parserInput.commentStore.length = 0;
                     if (s.condition && selectors.length > 1) {
-                        error("Guards are only currently allowed on a single selector.");
+                        error('Guards are only currently allowed on a single selector.');
                     }
                     if (!parserInput.$char(',')) { break; }
                     if (s.condition) {
-                        error("Guards are only currently allowed on a single selector.");
+                        error('Guards are only currently allowed on a single selector.');
                     }
                     parserInput.commentStore.length = 0;
                 }
@@ -1413,7 +1412,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 let cif;
 
                 if (!(key = entities.variableCurly())) {
-                    key = expect(/^(?:[_A-Za-z0-9-\*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
+                    key = expect(/^(?:[_A-Za-z0-9-*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
                 }
 
                 op = parserInput.$re(/^[|~*$^]?=/);
@@ -1580,7 +1579,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
             },
             anonymousValue: function () {
                 const index = parserInput.i;
-                const match = parserInput.$re(/^([^.#@\$+\/'"*`(;{}-]*);/);
+                const match = parserInput.$re(/^([^.#@$+/'"*`(;{}-]*);/);
                 if (match) {
                     return new(tree.Anonymous)(match[1], index + currentIndex);
                 }
@@ -1890,7 +1889,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     parserInput.restore();
                     return null;
                 }
-                const args = parserInput.$re(/^\s*([^\);]+)\)\s*/);
+                const args = parserInput.$re(/^\s*([^);]+)\)\s*/);
                 if (args[1]) {
                     parserInput.forget();
                     return args[1].trim();
@@ -2057,7 +2056,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 if (m) {
                     isSpaced = parserInput.isWhitespace(-1);
                     while (true) {
-                        if (parserInput.peek(/^\/[*\/]/)) {
+                        if (parserInput.peek(/^\/[*/]/)) {
                             break;
                         }
 
@@ -2232,7 +2231,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 parserInput.forget();
                 return body;
             },
-            atomicCondition: function (needsParens) {
+            atomicCondition: function () {
                 const entities = this.entities;
                 const index = parserInput.i;
                 let a;
@@ -2240,10 +2239,9 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 let c;
                 let op;
 
-                function cond() {
+                const cond = (function() {
                     return this.addition() || entities.keyword() || entities.quoted() || entities.mixinLookup();
-                }
+                }).bind(this)
-                cond = cond.bind(this);
 
                 a = cond();
                 if (a) {
@@ -2292,7 +2290,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                 const entities = this.entities;
                 let negate;
 
-                if (parserInput.peek(/^-[@\$\(]/)) {
+                if (parserInput.peek(/^-[@$(]/)) {
                     negate = parserInput.$char('-');
                 }
 
@@ -2338,7 +2336,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     if (e) {
                         entities.push(e);
                         // operations do not allow keyword "/" dimension (e.g. small/20px) so we support that here
-                        if (!parserInput.peek(/^\/[\/*]/)) {
+                        if (!parserInput.peek(/^\/[/*]/)) {
                             delim = parserInput.$char('/');
                             if (delim) {
                                 entities.push(new(tree.Anonymous)(delim, index + currentIndex));
@@ -2382,7 +2380,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
 
                 match(/^(\*?)/);
                 while (true) {
-                    if (!match(/^((?:[\w-]+)|(?:[@\$]\{[\w-]+\}))/)) {
+                    if (!match(/^((?:[\w-]+)|(?:[@$]\{[\w-]+\}))/)) {
                         break;
                     }
                 }

packages/less/src/less/render.js

@@ -1,6 +1,6 @@
 import * as utils from './utils';
 
-export default function(environment, ParseTree, ImportManager) {
+export default function(environment, ParseTree) {
     const render = function (input, options, callback) {
         if (typeof options === 'function') {
             callback = options;
@@ -38,4 +38,4 @@ export default function(environment, ParseTree, ImportManager) {
     };
 
     return render;
-};
+}

packages/less/src/less/source-map-builder.js

@@ -79,4 +79,4 @@ export default function (SourceMapOutput, environment) {
     }
 
     return SourceMapBuilder;
-};
+}

packages/less/src/less/source-map-output.js

@@ -116,6 +116,7 @@ export default function (environment) {
 
             if (this._outputSourceFiles) {
                 for (const filename in this._contentsMap) {
+                    // eslint-disable-next-line no-prototype-builtins
                     if (this._contentsMap.hasOwnProperty(filename)) {
                         let source = this._contentsMap[filename];
                         if (this._contentsIgnoredCharsMap[filename]) {
@@ -147,4 +148,4 @@ export default function (environment) {
     }
 
     return SourceMapOutput;
-};
+}

packages/less/src/less/transform-tree.js

@@ -54,7 +54,7 @@ export default function(root, options) {
      */
     if (options.pluginManager) {
         visitorIterator = options.pluginManager.visitor();
-        for (var i = 0; i < 2; i++) {
+        for (let i = 0; i < 2; i++) {
             visitorIterator.first();
             while ((v = visitorIterator.get())) {
                 if (v.isPreEvalVisitor) {
@@ -79,7 +79,7 @@ export default function(root, options) {
 
     evaldRoot = root.eval(evalEnv);
 
-    for (var i = 0; i < visitors.length; i++) {
+    for (let i = 0; i < visitors.length; i++) {
         visitors[i].run(evaldRoot);
     }
 
@@ -94,4 +94,4 @@ export default function(root, options) {
     }
 
     return evaldRoot;
-};
+}

packages/less/src/less/tree/attribute.js

@@ -32,7 +32,7 @@ Attribute.prototype = Object.assign(new Node(), {
         }
 
         if (this.cif) {
-            value = value + " " + this.cif;
+            value = value + ' ' + this.cif;
         }
 
         return `[${value}]`;

packages/less/src/less/tree/call.js

@@ -58,6 +58,7 @@ Call.prototype = Object.assign(new Node(), {
                 result = funcCaller.call(this.args);
                 exitCalc();
             } catch (e) {
+                // eslint-disable-next-line no-prototype-builtins
                 if (e.hasOwnProperty('line') && e.hasOwnProperty('column')) {
                     throw e;
                 }

packages/less/src/less/tree/color.js

@@ -96,6 +96,7 @@ Color.prototype = Object.assign(new Node(), {
                 break;
             case 'hsla':
                 args.push(clamp(alpha, 1));
+            // eslint-disable-next-line no-fallthrough
             case 'hsl':
                 color = this.toHSL();
                 args = [
@@ -212,6 +213,7 @@ Color.prototype = Object.assign(new Node(), {
 Color.fromKeyword = function(keyword) {
     let c;
     const key = keyword.toLowerCase();
+    // eslint-disable-next-line no-prototype-builtins
     if (colors.hasOwnProperty(key)) {
         c = new Color(colors[key].slice(1));
     }

packages/less/src/less/tree/debug-info.js

@@ -7,9 +7,9 @@ function asMediaQuery(ctx) {
     if (!/^[a-z]+:\/\//i.test(filenameWithProtocol)) {
         filenameWithProtocol = `file://${filenameWithProtocol}`;
     }
-    return `@media -sass-debug-info{filename{font-family:${filenameWithProtocol.replace(/([.:\/\\])/g, function (a) {
+    return `@media -sass-debug-info{filename{font-family:${filenameWithProtocol.replace(/([.:/\\])/g, function (a) {
         if (a == '\\') {
-            a = '\/';
+            a = '/';
         }
         return `\\${a}`;
     })}}line{font-family:\\00003${ctx.debugInfo.lineNumber}}}\n`;

packages/less/src/less/tree/dimension.js

@@ -1,3 +1,4 @@
+/* eslint-disable no-prototype-builtins */
 import Node from './node';
 import unitConversions from '../data/unit-conversions';
 import Unit from './unit';
@@ -23,6 +24,8 @@ Dimension.prototype = Object.assign(new Node(), {
         this.unit = visitor.visit(this.unit);
     },
 
+    // remove when Nodes have JSDoc types
+    // eslint-disable-next-line no-unused-vars
     eval(context) {
         return this;
     },
@@ -81,7 +84,7 @@ Dimension.prototype = Object.assign(new Node(), {
                 other = other.convertTo(this.unit.usedUnits());
 
                 if (context.strictUnits && other.unit.toString() !== unit.toString()) {
-                    throw new Error(`Incompatible units. Change the units or use the unit function. `
+                    throw new Error('Incompatible units. Change the units or use the unit function. '
                         + `Bad units: '${unit.toString()}' and '${other.unit.toString()}'.`);
                 }
 
@@ -144,7 +147,6 @@ Dimension.prototype = Object.assign(new Node(), {
             conversions = derivedConversions;
         }
         applyUnit = function (atomicUnit, denominator) {
-            /* jshint loopfunc:true */
             if (group.hasOwnProperty(atomicUnit)) {
                 if (denominator) {
                     value = value / (group[atomicUnit] / group[targetUnit]);

packages/less/src/less/tree/extend.js

@@ -35,6 +35,8 @@ Extend.prototype = Object.assign(new Node(), {
         return new Extend(this.selector.eval(context), this.option, this.getIndex(), this.fileInfo(), this.visibilityInfo());
     },
 
+    // remove when Nodes have JSDoc types
+    // eslint-disable-next-line no-unused-vars
     clone(context) {
         return new Extend(this.selector, this.option, this.getIndex(), this.fileInfo(), this.visibilityInfo());
     },

packages/less/src/less/tree/import.js

@@ -31,7 +31,7 @@ const Import = function(path, features, options, index, currentFileInfo, visibil
         this.css = !this.options.less || this.options.inline;
     } else {
         const pathValue = this.getPath();
-        if (pathValue && /[#\.\&\?]css([\?;].*)?$/.test(pathValue)) {
+        if (pathValue && /[#.&?]css([?;].*)?$/.test(pathValue)) {
             this.css = true;
         }
     }

packages/less/src/less/tree/js-eval-node.js

@@ -29,8 +29,8 @@ JsEvalNode.prototype = Object.assign(new Node(), {
 
         const variables = context.frames[0].variables();
         for (const k in variables) {
+            // eslint-disable-next-line no-prototype-builtins
             if (variables.hasOwnProperty(k)) {
-                /* jshint loopfunc:true */
                 evalContext[k.slice(1)] = {
                     value: variables[k].value,
                     toJS: function () {

packages/less/src/less/tree/namespace-value.js

@@ -14,7 +14,7 @@ NamespaceValue.prototype = Object.assign(new Node(), {
     type: 'NamespaceValue',
 
     eval(context) {
-        let i, j, name, rules = this.value.eval(context);
+        let i, name, rules = this.value.eval(context);
         
         for (i = 0; i < this.lookups.length; i++) {
             name = this.lookups[i];

packages/less/src/less/tree/node.js

@@ -1,10 +1,8 @@
-import * as utils from '../utils';
-
 /**
  * The reason why Node is a class and other nodes simply do not extend
  * from Node (since we're transpiling) is due to this issue:
  * 
- * https://github.com/less/less.js/issues/3434
+ * @see https://github.com/less/less.js/issues/3434
  */
 class Node {
     constructor() {
@@ -50,6 +48,8 @@ class Node {
     toCSS(context) {
         const strs = [];
         this.genCSS(context, {
+            // remove when genCSS has JSDoc types
+            // eslint-disable-next-line no-unused-vars
             add: function(chunk, fileInfo, index) {
                 strs.push(chunk);
             },

packages/less/src/less/tree/quoted.js

@@ -1,8 +1,6 @@
 import Node from './node';
 import Variable from './variable';
 import Property from './property';
-import * as utils from '../utils';
-
 
 const Quoted = function(str, content, escaped, index, currentFileInfo) {
     this.escaped = (escaped === undefined) ? true : escaped;

packages/less/src/less/tree/ruleset.js

@@ -45,7 +45,6 @@ Ruleset.prototype = Object.assign(new Node(), {
     },
 
     eval(context) {
-        const that = this;
         let selectors;
         let selCnt;
         let selector;
@@ -62,7 +61,7 @@ Ruleset.prototype = Object.assign(new Node(), {
 
             for (i = 0; i < selCnt; i++) {
                 selector = this.selectors[i].eval(context);
-                for (var j = 0; j < selector.elements.length; j++) {
+                for (let j = 0; j < selector.elements.length; j++) {
                     if (selector.elements[j].isVariable) {
                         hasVariable = true;
                         break;
@@ -84,7 +83,7 @@ Ruleset.prototype = Object.assign(new Node(), {
                 const selectorFileInfo = selectors[0].fileInfo();
                 new Parser(context, this.parse.importManager, selectorFileInfo, startingIndex).parseNode(
                     toParseSelectors.join(','),
-                    ["selectors"],
+                    ['selectors'],
                     function(err, result) {
                         if (result) {
                             selectors = utils.flattenArray(result);
@@ -201,7 +200,7 @@ Ruleset.prototype = Object.assign(new Node(), {
                 if (rule.selectors[0] && rule.selectors[0].isJustParentSelector()) {
                     rsRules.splice(i--, 1);
 
-                    for (var j = 0; (subRule = rule.rules[j]); j++) {
+                    for (let j = 0; (subRule = rule.rules[j]); j++) {
                         if (subRule instanceof Node) {
                             subRule.copyVisibilityInfo(rule.visibilityInfo());
                             if (!(subRule instanceof Declaration) || !subRule.variable) {
@@ -296,6 +295,7 @@ Ruleset.prototype = Object.assign(new Node(), {
                 if (r.type === 'Import' && r.root && r.root.variables) {
                     const vars = r.root.variables();
                     for (const name in vars) {
+                        // eslint-disable-next-line no-prototype-builtins
                         if (vars.hasOwnProperty(name)) {
                             hash[name] = r.root.variable(name);
                         }

packages/less/src/less/tree/selector.js

@@ -95,7 +95,7 @@ Selector.prototype = Object.assign(new Node(), {
 
         let elements = this.elements.map( function(v) {
             return v.combinator.value + (v.value.value || v.value);
-        }).join('').match(/[,&#\*\.\w-]([\w-]|(\\.))*/g);
+        }).join('').match(/[,&#*.\w-]([\w-]|(\\.))*/g);
 
         if (elements) {
             if (elements[0] === '&') {

packages/less/src/less/tree/unit.js

@@ -78,7 +78,7 @@ Unit.prototype = Object.assign(new Node(), {
         let groupName;
 
         mapUnit = function (atomicUnit) {
-            /* jshint loopfunc:true */
+            // eslint-disable-next-line no-prototype-builtins
             if (group.hasOwnProperty(atomicUnit) && !result[groupName]) {
                 result[groupName] = atomicUnit;
             }
@@ -87,6 +87,7 @@ Unit.prototype = Object.assign(new Node(), {
         };
 
         for (groupName in unitConversions) {
+            // eslint-disable-next-line no-prototype-builtins
             if (unitConversions.hasOwnProperty(groupName)) {
                 group = unitConversions[groupName];
 
@@ -116,6 +117,7 @@ Unit.prototype = Object.assign(new Node(), {
         this.denominator = [];
 
         for (atomicUnit in counter) {
+            // eslint-disable-next-line no-prototype-builtins
             if (counter.hasOwnProperty(atomicUnit)) {
                 const count = counter[atomicUnit];
 

packages/less/src/less/tree/url.js

@@ -1,7 +1,7 @@
 import Node from './node';
 
 function escapePath(path) {
-    return path.replace(/[\(\)'"\s]/g, function(match) { return `\\${match}`; });
+    return path.replace(/[()'"\s]/g, function(match) { return `\\${match}`; });
 }
 
 const URL = function(val, index, currentFileInfo, isEvald) {
@@ -33,7 +33,7 @@ URL.prototype = Object.assign(new Node(), {
             rootpath = this.fileInfo() && this.fileInfo().rootpath;
             if (typeof rootpath === 'string' &&
                 typeof val.value === 'string' &&
-                context.pathRequiresRewrite(val.value)) {
+                context.pathRequiresRewrite(val.value)) {
                 if (!val.quote) {
                     rootpath = escapePath(rootpath);
                 }

packages/less/src/less/utils.js

@@ -35,7 +35,7 @@ export function copyArray(arr) {
 export function clone(obj) {
     const cloned = {};
     for (const prop in obj) {
-        if (obj.hasOwnProperty(prop)) {
+        if (Object.prototype.hasOwnProperty.call(obj, prop)) {
             cloned[prop] = obj[prop];
         }
     }
@@ -100,7 +100,7 @@ export function copyOptions(obj1, obj2) {
 
 export function merge(obj1, obj2) {
     for (const prop in obj2) {
-        if (obj2.hasOwnProperty(prop)) {
+        if (Object.prototype.hasOwnProperty.call(obj2, prop)) {
             obj1[prop] = obj2[prop];
         }
     }

packages/less/src/less/visitors/extend-visitor.js

@@ -1,3 +1,7 @@
+/* eslint-disable no-unused-vars */
+/**
+ * @todo - Remove unused when JSDoc types are added for visitor methods
+ */
 import tree from '../tree';
 import Visitor from './visitor';
 import logger from '../logger';

packages/less/src/less/visitors/import-visitor.js

@@ -1,3 +1,7 @@
+/* eslint-disable no-unused-vars */
+/**
+ * @todo - Remove unused when JSDoc types are added for visitor methods
+ */
 import contexts from '../contexts';
 import Visitor from './visitor';
 import ImportSequencer from './import-sequencer';

packages/less/src/less/visitors/join-selector-visitor.js

@@ -1,3 +1,7 @@
+/* eslint-disable no-unused-vars */
+/**
+ * @todo - Remove unused when JSDoc types are added for visitor methods
+ */
 import Visitor from './visitor';
 
 class JoinSelectorVisitor {

packages/less/src/less/visitors/to-css-visitor.js

@@ -1,3 +1,7 @@
+/* eslint-disable no-unused-vars */
+/**
+ * @todo - Remove unused when JSDoc types are added for visitor methods
+ */
 import tree from '../tree';
 import Visitor from './visitor';
 

packages/less/test/browser/generator/benchmark.config.js

@@ -3,48 +3,48 @@ module.exports = {
     current: {
     // src is used to build list of less files to compile
         src: [
-            "benchmark/benchmark.less"
+            'benchmark/benchmark.less'
         ],
         options: {
-            helpers: "benchmark/browseroptions.js",
+            helpers: 'benchmark/browseroptions.js',
-            specs: "benchmark/browserspec.js",
+            specs: 'benchmark/browserspec.js',
-            outfile: "tmp/browser/test-runner-benchmark-current.html"
+            outfile: 'tmp/browser/test-runner-benchmark-current.html'
         }
     },
     v3_10_3: {
         // src is used to build list of less files to compile
         src: [
-            "benchmark/benchmark.less"
+            'benchmark/benchmark.less'
         ],
         options: {
-            helpers: "benchmark/browseroptions.js",
+            helpers: 'benchmark/browseroptions.js',
-            specs: "benchmark/browserspec.js",
+            specs: 'benchmark/browserspec.js',
-            outfile: "tmp/browser/test-runner-benchmark-v3_10_3.html",
+            outfile: 'tmp/browser/test-runner-benchmark-v3_10_3.html',
-            less: "https://cdnjs.cloudflare.com/ajax/libs/less.js/3.10.3/less.min.js"
+            less: 'https://cdnjs.cloudflare.com/ajax/libs/less.js/3.10.3/less.min.js'
         }
     },
     v3_9_0: {
         // src is used to build list of less files to compile
         src: [
-            "benchmark/benchmark.less"
+            'benchmark/benchmark.less'
         ],
         options: {
-            helpers: "benchmark/browseroptions.js",
+            helpers: 'benchmark/browseroptions.js',
-            specs: "benchmark/browserspec.js",
+            specs: 'benchmark/browserspec.js',
-            outfile: "tmp/browser/test-runner-benchmark-v3_9_0.html",
+            outfile: 'tmp/browser/test-runner-benchmark-v3_9_0.html',
-            less: "https://cdnjs.cloudflare.com/ajax/libs/less.js/3.9.0/less.min.js"
+            less: 'https://cdnjs.cloudflare.com/ajax/libs/less.js/3.9.0/less.min.js'
         }
     },
     v2_7_3: {
         // src is used to build list of less files to compile
         src: [
-            "benchmark/benchmark.less"
+            'benchmark/benchmark.less'
         ],
         options: {
-            helpers: "benchmark/browseroptions.js",
+            helpers: 'benchmark/browseroptions.js',
-            specs: "benchmark/browserspec.js",
+            specs: 'benchmark/browserspec.js',
-            outfile: "tmp/browser/test-runner-benchmark-v2_7_3.html",
+            outfile: 'tmp/browser/test-runner-benchmark-v2_7_3.html',
-            less: "https://cdnjs.cloudflare.com/ajax/libs/less.js/2.7.3/less.min.js"
+            less: 'https://cdnjs.cloudflare.com/ajax/libs/less.js/2.7.3/less.min.js'
         }
     }
 }

packages/less/test/browser/generator/runner.config.js

@@ -19,168 +19,168 @@ module.exports = {
             `!${lessFolder}/_main/empty.less`
         ],
         options: {
-            helpers: "test/browser/runner-main-options.js",
+            helpers: 'test/browser/runner-main-options.js',
-            specs: "test/browser/runner-main-spec.js",
+            specs: 'test/browser/runner-main-spec.js',
-            outfile: "tmp/browser/test-runner-main.html"
+            outfile: 'tmp/browser/test-runner-main.html'
         }
     },
     legacy: {
         src: [`${lessFolder}/legacy/*.less`],
         options: {
-            helpers: "test/browser/runner-legacy-options.js",
+            helpers: 'test/browser/runner-legacy-options.js',
-            specs: "test/browser/runner-legacy-spec.js",
+            specs: 'test/browser/runner-legacy-spec.js',
-            outfile: "tmp/browser/test-runner-legacy.html"
+            outfile: 'tmp/browser/test-runner-legacy.html'
         }
     },
     strictUnits: {
         src: [`${lessFolder}/strict-units/*.less`],
         options: {
-            helpers: "test/browser/runner-strict-units-options.js",
+            helpers: 'test/browser/runner-strict-units-options.js',
-            specs: "test/browser/runner-strict-units-spec.js",
+            specs: 'test/browser/runner-strict-units-spec.js',
-            outfile: "tmp/browser/test-runner-strict-units.html"
+            outfile: 'tmp/browser/test-runner-strict-units.html'
         }
     },
     errors: {
         src: [
             `${lessFolder}/errors/*.less`,
             `${testFolder}/errors/javascript-error.less`,
-            "test/browser/less/errors/*.less"
+            'test/browser/less/errors/*.less'
         ],
         options: {
             timeout: 20000,
-            helpers: "test/browser/runner-errors-options.js",
+            helpers: 'test/browser/runner-errors-options.js',
-            specs: "test/browser/runner-errors-spec.js",
+            specs: 'test/browser/runner-errors-spec.js',
-            outfile: "tmp/browser/test-runner-errors.html"
+            outfile: 'tmp/browser/test-runner-errors.html'
         }
     },
     noJsErrors: {
         src: [`${lessFolder}/no-js-errors/*.less`],
         options: {
-            helpers: "test/browser/runner-no-js-errors-options.js",
+            helpers: 'test/browser/runner-no-js-errors-options.js',
-            specs: "test/browser/runner-no-js-errors-spec.js",
+            specs: 'test/browser/runner-no-js-errors-spec.js',
-            outfile: "tmp/browser/test-runner-no-js-errors.html"
+            outfile: 'tmp/browser/test-runner-no-js-errors.html'
         }
     },
     browser: {
         src: [
-            "test/browser/less/*.less",
+            'test/browser/less/*.less',
-            "test/browser/less/plugin/*.less"
+            'test/browser/less/plugin/*.less'
         ],
         options: {
-            helpers: "test/browser/runner-browser-options.js",
+            helpers: 'test/browser/runner-browser-options.js',
-            specs: "test/browser/runner-browser-spec.js",
+            specs: 'test/browser/runner-browser-spec.js',
-            outfile: "tmp/browser/test-runner-browser.html"
+            outfile: 'tmp/browser/test-runner-browser.html'
         }
     },
     relativeUrls: {
-        src: ["test/browser/less/relative-urls/*.less"],
+        src: ['test/browser/less/relative-urls/*.less'],
         options: {
-            helpers: "test/browser/runner-relative-urls-options.js",
+            helpers: 'test/browser/runner-relative-urls-options.js',
-            specs: "test/browser/runner-relative-urls-spec.js",
+            specs: 'test/browser/runner-relative-urls-spec.js',
-            outfile: "tmp/browser/test-runner-relative-urls.html"
+            outfile: 'tmp/browser/test-runner-relative-urls.html'
         }
     },
     rewriteUrls: {
-        src: ["test/browser/less/rewrite-urls/*.less"],
+        src: ['test/browser/less/rewrite-urls/*.less'],
         options: {
-            helpers: "test/browser/runner-rewrite-urls-options.js",
+            helpers: 'test/browser/runner-rewrite-urls-options.js',
-            specs: "test/browser/runner-rewrite-urls-spec.js",
+            specs: 'test/browser/runner-rewrite-urls-spec.js',
-            outfile: "tmp/browser/test-runner-rewrite-urls.html"
+            outfile: 'tmp/browser/test-runner-rewrite-urls.html'
         }
     },
     rootpath: {
-        src: ["test/browser/less/rootpath/*.less"],
+        src: ['test/browser/less/rootpath/*.less'],
         options: {
-            helpers: "test/browser/runner-rootpath-options.js",
+            helpers: 'test/browser/runner-rootpath-options.js',
-            specs: "test/browser/runner-rootpath-spec.js",
+            specs: 'test/browser/runner-rootpath-spec.js',
-            outfile: "tmp/browser/test-runner-rootpath.html"
+            outfile: 'tmp/browser/test-runner-rootpath.html'
         }
     },
     rootpathRelative: {
-        src: ["test/browser/less/rootpath-relative/*.less"],
+        src: ['test/browser/less/rootpath-relative/*.less'],
         options: {
-            helpers: "test/browser/runner-rootpath-relative-options.js",
+            helpers: 'test/browser/runner-rootpath-relative-options.js',
-            specs: "test/browser/runner-rootpath-relative-spec.js",
+            specs: 'test/browser/runner-rootpath-relative-spec.js',
-            outfile: "tmp/browser/test-runner-rootpath-relative.html"
+            outfile: 'tmp/browser/test-runner-rootpath-relative.html'
         }
     },
     rootpathRewriteUrls: {
-        src: ["test/browser/less/rootpath-rewrite-urls/*.less"],
+        src: ['test/browser/less/rootpath-rewrite-urls/*.less'],
         options: {
             helpers:
-            "test/browser/runner-rootpath-rewrite-urls-options.js",
+            'test/browser/runner-rootpath-rewrite-urls-options.js',
-            specs: "test/browser/runner-rootpath-rewrite-urls-spec.js",
+            specs: 'test/browser/runner-rootpath-rewrite-urls-spec.js',
             outfile:
-            "tmp/browser/test-runner-rootpath-rewrite-urls.html"
+            'tmp/browser/test-runner-rootpath-rewrite-urls.html'
         }
     },
     production: {
-        src: ["test/browser/less/production/*.less"],
+        src: ['test/browser/less/production/*.less'],
         options: {
-            helpers: "test/browser/runner-production-options.js",
+            helpers: 'test/browser/runner-production-options.js',
-            specs: "test/browser/runner-production-spec.js",
+            specs: 'test/browser/runner-production-spec.js',
-            outfile: "tmp/browser/test-runner-production.html"
+            outfile: 'tmp/browser/test-runner-production.html'
         }
     },
     modifyVars: {
-        src: ["test/browser/less/modify-vars/*.less"],
+        src: ['test/browser/less/modify-vars/*.less'],
         options: {
-            helpers: "test/browser/runner-modify-vars-options.js",
+            helpers: 'test/browser/runner-modify-vars-options.js',
-            specs: "test/browser/runner-modify-vars-spec.js",
+            specs: 'test/browser/runner-modify-vars-spec.js',
-            outfile: "tmp/browser/test-runner-modify-vars.html"
+            outfile: 'tmp/browser/test-runner-modify-vars.html'
         }
     },
     globalVars: {
-        src: ["test/browser/less/global-vars/*.less"],
+        src: ['test/browser/less/global-vars/*.less'],
         options: {
-            helpers: "test/browser/runner-global-vars-options.js",
+            helpers: 'test/browser/runner-global-vars-options.js',
-            specs: "test/browser/runner-global-vars-spec.js",
+            specs: 'test/browser/runner-global-vars-spec.js',
-            outfile: "tmp/browser/test-runner-global-vars.html"
+            outfile: 'tmp/browser/test-runner-global-vars.html'
         }
     },
     postProcessorPlugin: {
         src: [`${lessFolder}/postProcessorPlugin/*.less`],
         options: {
             helpers: [
-                `test/plugins/postprocess/index.js`,
+                'test/plugins/postprocess/index.js',
-                "test/browser/runner-postProcessorPlugin-options.js"
+                'test/browser/runner-postProcessorPlugin-options.js'
             ],
-            specs: "test/browser/runner-postProcessorPlugin.js",
+            specs: 'test/browser/runner-postProcessorPlugin.js',
             outfile:
-            "tmp/browser/test-runner-post-processor-plugin.html"
+            'tmp/browser/test-runner-post-processor-plugin.html'
         }
     },
     preProcessorPlugin: {
         src: [`${lessFolder}/preProcessorPlugin/*.less`],
         options: {
             helpers: [
-                `test/plugins/preprocess/index.js`,
+                'test/plugins/preprocess/index.js',
-                "test/browser/runner-preProcessorPlugin-options.js"
+                'test/browser/runner-preProcessorPlugin-options.js'
             ],
-            specs: "test/browser/runner-preProcessorPlugin.js",
+            specs: 'test/browser/runner-preProcessorPlugin.js',
-            outfile: "tmp/browser/test-runner-pre-processor-plugin.html"
+            outfile: 'tmp/browser/test-runner-pre-processor-plugin.html'
         }
     },
     visitorPlugin: {
         src: [`${lessFolder}/visitorPlugin/*.less`],
         options: {
             helpers: [
-                `test/plugins/visitor/index.js`,
+                'test/plugins/visitor/index.js',
-                "test/browser/runner-VisitorPlugin-options.js"
+                'test/browser/runner-VisitorPlugin-options.js'
             ],
-            specs: "test/browser/runner-VisitorPlugin.js",
+            specs: 'test/browser/runner-VisitorPlugin.js',
-            outfile: "tmp/browser/test-runner-visitor-plugin.html"
+            outfile: 'tmp/browser/test-runner-visitor-plugin.html'
         }
     },
     filemanagerPlugin: {
         src: [`${lessFolder}/filemanagerPlugin/*.less`],
         options: {
             helpers: [
-                `test/plugins/filemanager/index.js`,
+                'test/plugins/filemanager/index.js',
-                "test/browser/runner-filemanagerPlugin-options.js"
+                'test/browser/runner-filemanagerPlugin-options.js'
             ],
-            specs: "test/browser/runner-filemanagerPlugin.js",
+            specs: 'test/browser/runner-filemanagerPlugin.js',
-            outfile: "tmp/browser/test-runner-filemanager-plugin.html"
+            outfile: 'tmp/browser/test-runner-filemanager-plugin.html'
         }
     }
 }

packages/less/test/browser/runner-rewrite-urls-spec.js

@@ -1,3 +1,3 @@
-describe("less.js browser test - rewrite urls", function() {
+describe('less.js browser test - rewrite urls', function() {
     testLessEqualsInDocument();
 });

packages/less/test/plugins/filemanager/index.js

@@ -1,7 +1,7 @@
 (function(exports) {
     var plugin = function(less) {
         var FileManager = less.FileManager, TestFileManager = new FileManager();
-        function TestFileManager() { };
+        function TestFileManager() { }
         TestFileManager.loadFile = function (filename, currentDirectory, options, environment, callback) {
             if (filename.match(/.*\.test$/)) {
                 return less.environment.fileManagers[0].loadFile('colors.test', currentDirectory, options, environment, callback);

packages/less/test/test-es6.ts

@@ -2,16 +2,16 @@
 console.log('Testing ES6 imports...')
 
 import less from '..';
-let lessRender = less.render;
+const lessRender = less.render;
 
 // then I call lessRender on something
-let y = lessRender(`
+lessRender(`
 body {
     a: 1;
     b: 2;
     c: 30;
     d: 4;
-}`, {sourceMap: {}},  function(error, output) {
+}`, {sourceMap: {}},  function(error: any, output: any) {
-  if (error)
+    if (error)
-    console.error(error)
+        console.error(error)
 })

packages/less/tsconfig.build.json

@@ -0,0 +1,7 @@
+{
+  "extends": "./tsconfig",
+  "compilerOptions": {
+    "rootDir": "./src",
+  },
+  "include": ["src/**/*"]
+}

packages/less/tsconfig.json

@@ -1,12 +1,13 @@
 {
   "compilerOptions": {
     "outDir": "./lib",
-    "rootDir": "./src",
+    "rootDir": ".",
     "allowJs": true,
     "sourceMap": true,
     "inlineSources": true,
     "esModuleInterop": true,
     "importHelpers": true,
+    "noImplicitAny": true,
     "target": "ES5"
   },
   "ts-node": {
@@ -14,6 +15,6 @@
       "rootDir": "."
     }
   },
-  "include": ["src/**/*"],
+  "include": ["**/*"],
-  "exclude": ["node_modules"]
+  "exclude": ["node_modules", "lib/**/*"]
 }