Build: Improve ESLint configuration, check all test files as well

The new ESLint setup is largely based on the current jQuery Core one.

Closes jquerygh-339

Author: mgol

.eslintrc-browser.json

@@ -0,0 +1,30 @@
+{
+	"root": true,
+
+	"extends": "jquery",
+
+	// Support: IE <=9 only, Android <=4.0 only
+	// The above browsers are failing a lot of tests in the ES5
+	// test suite at http://test262.ecmascript.org.
+	"parserOptions": {
+		"ecmaVersion": 3
+	},
+
+	// The browser env is not enabled on purpose so that code takes
+	// all browser-only globals from window instead of assuming
+	// they're available as globals. This makes it possible to use
+	// jQuery with tools like jsdom which provide a custom window
+	// implementation.
+	"env": {},
+
+	"globals": {
+		"window": true,
+		"define": true,
+		"module": true
+	},
+
+	"rules": {
+		"one-var": ["error", {"var": "always"}],
+		"strict": ["error", "function"]
+	}
+}

.eslintrc-node.json

@@ -0,0 +1,18 @@
+{
+	"root": true,
+
+	"extends": "jquery",
+
+	"parserOptions": {
+		"ecmaVersion": 2017
+	},
+
+	"env": {
+		"es6": true,
+		"node": true
+	},
+
+	"rules": {
+		"strict": ["error", "global"]
+	}
+}

.eslintrc.json

@@ -1,8 +1,5 @@
 {
-	"extends": "jquery",
 	"root": true,
-	"env": {
-		"browser": false,
-		"node": true
-	}
+
+	"extends": "./.eslintrc-node.json"
 }

Gruntfile.js

@@ -1,7 +1,8 @@
-/*global module:false*/
-module.exports = function( grunt ) {
+"use strict";
+
+/* global module:false */
 
-	"use strict";
+module.exports = function( grunt ) {
 
 	var isTravis = process.env.TRAVIS;
 

build/release.js

@@ -3,6 +3,8 @@
  * JQuery Migrate Plugin Release Management
  */
 
+"use strict";
+
 // Debugging variables
 var	dryrun = false,
 	skipRemote = false;

dist/.eslintrc.json

@@ -3,6 +3,7 @@
 	"root": true,
 	"rules": {
 		// That is okay for the built version
-		"no-multiple-empty-lines": "off"
+		"no-multiple-empty-lines": "off",
+		"one-var": "off"
 	}
 }