Add allowThis option to no-mutation

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 `allowThis` option to [`no-mutation`]
 
 ## [1.2.0] - 2016-06-21
 ### Added

docs/rules/no-mutation.md

@@ -8,13 +8,16 @@ This rule supports the following options:
 
 `commonjs`: If set to `true`, then this rule will not report when assigning to or to a (sub-) property of `exports` or `module.exports`. Note that this will not report when reassigning or overwriting previous exports.
 
+`allowThis`: If set to `true`, then this rule will not report when assigning to or to a (sub-) property of `this`.
+
 `exceptions`: List of objects that describe exceptions to the rule. Each exception should have either or both `object` and `property` field set.
 
 You can set the options like this:
 
 ```js
 "fp/no-mutation": ["error", {
   "commonjs": true,
+  "allowThis": true,
   "exceptions": [
     {"object": "foo", "property": "bar"}
   ]

rules/no-mutation.js

@@ -71,6 +71,9 @@ module.exports = function (context) {
   var options = context.options[0] || {};
   var acceptCommonJs = options.commonjs;
   var exceptions = _.map(makeException, options.exceptions);
+  if (options.allowThis) {
+    exceptions.push(_.matches({type: 'MemberExpression', object: {type: 'ThisExpression'}}));
+  }
   return {
     AssignmentExpression: function (node) {
       var isCommonJs = isCommonJsExport(node);
@@ -97,6 +100,9 @@ module.exports.schema = [{
     commonjs: {
       type: 'boolean'
     },
+    allowThis: {
+      type: 'boolean'
+    },
     exceptions: {
       type: 'array',
       items: {

test/no-mutation.js

@@ -93,6 +93,18 @@ ruleTester.run('no-mutation', rule, {
         {object: 'foo', property: 'bar'},
         {object: 'module', property: 'exports'}
       ]}]
+    },
+    {
+      code: 'this.foo = 100;',
+      options: [{allowThis: true}]
+    },
+    {
+      code: 'this.foo.bar = 100;',
+      options: [{allowThis: true}]
+    },
+    {
+      code: 'function bar() { this.foo = 100; }',
+      options: [{allowThis: true}]
     }
   ],
   invalid: [
@@ -217,6 +229,18 @@ ruleTester.run('no-mutation', rule, {
       code: 'baz.propTypes = {};',
       options: [{exceptions: [{}]}],
       errors: [reassignmentError]
+    },
+    {
+      code: 'this.foo = 100;',
+      errors: [reassignmentError]
+    },
+    {
+      code: 'this.foo.bar = 100;',
+      errors: [reassignmentError]
+    },
+    {
+      code: 'function bar() { this.foo = 100; }',
+      errors: [reassignmentError]
     }
   ]
 });