Add no-events rule

Author: jfmengels

CHANGELOG.md

@@ -4,7 +4,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 This change log adheres to standards from [Keep a CHANGELOG](http://keepachangelog.com).
 
 ## [Unreleased]
-- (none)
+### Added
+- Added [`no-events`] rule
 
 ## [1.1.0] - 2016-06-16
 ### Added

docs/rules/no-events.md

@@ -0,0 +1,13 @@
+# Forbid the use of the `events` module
+
+The use of `EventEmitter` with the `events` module provided by Node.js promotes implicit side-effects by emitting and listening to events. Instead of `events`, you should prefer activating the wanted effects by calling the functions you wish to use explicitly.
+
+The rule will simply warn whenever the `events` module is imported.
+
+### Fail
+
+```js
+import EventEmitter from 'events';
+
+const EventEmitter = require('events')
+```

index.js

@@ -4,6 +4,7 @@ module.exports = {
   rules: {
     'no-class': require('./rules/no-class'),
     'no-delete': require('./rules/no-delete'),
+    'no-events': require('./rules/no-let'),
     'no-let': require('./rules/no-let'),
     'no-loops': require('./rules/no-loops'),
     'no-mutating-assign': require('./rules/no-mutating-assign'),
@@ -19,6 +20,7 @@ module.exports = {
         'no-var': 'error',
         'fp/no-class': 'error',
         'fp/no-delete': 'error',
+        'fp/no-events': 'error',
         'fp/no-let': 'error',
         'fp/no-loops': 'error',
         'fp/no-mutating-assign': 'error',

readme.md

@@ -27,6 +27,7 @@ Configure it in `package.json`.
       "no-var": "error",
       "fp/no-class": "error",
       "fp/no-delete": "error",
+      "fp/no-events": "error",
       "fp/no-let": "error",
       "fp/no-loops": "error",
       "fp/no-mutating-assign": "error",
@@ -45,6 +46,7 @@ Configure it in `package.json`.
 
 - [no-class](docs/rules/no-class.md) - Forbid the use of `class`.
 - [no-delete](docs/rules/no-delete.md) - Forbid the use of `delete`.
+- [no-events](docs/rules/no-events.md) - Forbid the use of the `events` module.
 - [no-let](docs/rules/no-let.md) - Forbid the use of `let`.
 - [no-loops](docs/rules/no-loops.md) - Forbid the use of loops.
 - [no-mutating-assign](docs/rules/no-mutating-assign.md) - Forbid the use of [`Object.assign()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign) with a variable as first argument.

rules/no-events.js

@@ -0,0 +1,32 @@
+'use strict';
+
+function isStaticRequire(node) {
+  return node &&
+    node.callee &&
+    node.callee.type === 'Identifier' &&
+    node.callee.name === 'require' &&
+    node.arguments.length === 1 &&
+    node.arguments[0].type === 'Literal';
+}
+
+function report(context, node) {
+  context.report({
+    node: node,
+    message: 'Unallowed use of `events`'
+  });
+}
+
+module.exports = function (context) {
+  return {
+    ImportDeclaration: function (node) {
+      if (node.source.value === 'events') {
+        report(context, node);
+      }
+    },
+    CallExpression: function (node) {
+      if (isStaticRequire(node) && node.arguments[0].value === 'events') {
+        report(context, node);
+      }
+    }
+  };
+};

test/no-events.js

@@ -0,0 +1,44 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/no-events';
+
+const ruleTester = avaRuleTester(test, {
+  env: {
+    es6: true
+  },
+  parserOptions: {
+    sourceType: 'module'
+  }
+});
+
+const error = {
+  ruleId: 'no-events',
+  message: 'Unallowed use of `events`'
+};
+
+ruleTester.run('no-events', rule, {
+  valid: [
+    'import foo from "foo"',
+    'import {bar} from "foo"',
+    'import events from "eventsE"',
+    'import events from "Eevents"',
+    'require("foo");',
+    'require("eventsE");',
+    'require("Efoo");',
+    'var events;'
+  ],
+  invalid: [
+    {
+      code: 'import EventEmitter from "events";',
+      errors: [error]
+    },
+    {
+      code: 'import {listen} from "events";',
+      errors: [error]
+    },
+    {
+      code: 'require("events");',
+      errors: [error]
+    }
+  ]
+});