tools: add Node.js-specific ESLint rules

Add these rules:

* no-restricted-modules: See
http://eslint.org/docs/rules/no-restricted-modules. It has been
configured to prohibit the use of the deprecated `sys` and `_linklist`
modules.
* no-new-require: See http://eslint.org/docs/rules/no-new-require
* no-mixed-requires: http://eslint.org/docs/rules/no-mixed-requires

PR-URL: #5320
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

.eslintrc

@@ -31,6 +31,18 @@ rules:
   no-octal: 2
   no-redeclare: 2
 
+  # Variables
+  # http://eslint.org/docs/rules/#variables
+  no-delete-var: 2
+  no-undef: 2
+  no-unused-vars: [2, {"args": "none"}]
+
+  # Node.js and CommonJS
+  # http://eslint.org/docs/rules/#nodejs-and-commonjs
+  no-mixed-requires: 2
+  no-new-require: 2
+  no-restricted-modules: [2, "sys", "_linklist"]
+
   # Stylistic Issues
   # https://github.com/eslint/eslint/tree/master/docs/rules#stylistic-issues
   comma-spacing: 2
@@ -66,12 +78,6 @@ rules:
   # https://github.com/eslint/eslint/tree/master/docs/rules#strict-mode
   strict: [2, "global"]
 
-  # Variables
-  # https://github.com/eslint/eslint/tree/master/docs/rules#variables
-  no-delete-var: 2
-  no-undef: 2
-  no-unused-vars: [2, {"args": "none"}]
-
   # Custom rules in tools/eslint-rules
   require-buffer: 2
   new-with-error: [2, "Error", "RangeError", "TypeError", "SyntaxError", "ReferenceError"]

lib/timers.js

@@ -1,7 +1,7 @@
 'use strict';
 
 const Timer = process.binding('timer_wrap').Timer;
-const L = require('_linklist');
+const L = require('_linklist'); // eslint-disable-line no-restricted-modules
 const assert = require('assert').ok;
 const util = require('util');
 const debug = util.debuglog('timer');

test/parallel/test-sys.js

@@ -1,7 +1,7 @@
 'use strict';
 require('../common');
 var assert = require('assert');
-var sys = require('sys');
+var sys = require('sys'); // eslint-disable-line no-restricted-modules
 var util = require('util');
 
 assert.strictEqual(sys, util);

test/parallel/test-timers-linked-list.js

@@ -1,7 +1,7 @@
 'use strict';
 require('../common');
 const assert = require('assert');
-const L = require('_linklist');
+const L = require('_linklist'); // eslint-disable-line no-restricted-modules
 
 var list = { name: 'list' };
 var A = { name: 'A' };