Add no-extend rule. Closes #24

Author: brendo

README.md

@@ -41,6 +41,7 @@ Add `jquery` to the plugins section of your `.eslintrc` configuration file. You
     "jquery/no-deferred": 2,
     "jquery/no-delegate": 2,
     "jquery/no-each": 2,
+    "jquery/no-extend": 2,
     "jquery/no-fade": 2,
     "jquery/no-filter": 2,
     "jquery/no-find": 2,

index.js

@@ -15,6 +15,7 @@ module.exports = {
     'no-deferred': require('./rules/no-deferred'),
     'no-delegate': require('./rules/no-delegate'),
     'no-each': require('./rules/no-each'),
+    'no-extend': require('./rules/no-extend'),
     'no-fade': require('./rules/no-fade'),
     'no-filter': require('./rules/no-filter'),
     'no-find': require('./rules/no-find'),

rules/no-extend.js

@@ -0,0 +1,18 @@
+'use strict'
+
+module.exports = function(context) {
+  return {
+    CallExpression: function(node) {
+      if (node.callee.type !== 'MemberExpression') return
+      if (node.callee.object.name !== '$') return
+      if (node.callee.property.name !== 'extend') return
+
+      context.report({
+        node: node,
+        message: 'Prefer Object#assign or the spread operator to $.extend'
+      })
+    }
+  }
+}
+
+module.exports.schema = []

tests/no-extend.js

@@ -0,0 +1,17 @@
+'use strict'
+
+const rule = require('../rules/no-extend')
+const RuleTester = require('eslint').RuleTester
+
+const error = 'Prefer Object#assign or the spread operator to $.extend'
+
+const ruleTester = new RuleTester()
+ruleTester.run('no-extend', rule, {
+  valid: ['extend()', 'myMethod.extend()', 'myMethod.extend'],
+  invalid: [
+    {
+      code: '$.extend()',
+      errors: [{message: error, type: 'CallExpression'}]
+    }
+  ]
+})