rename rule no-unnecessary-bind to callback-binding with explanation …

…about shared settings

README.md

@@ -18,10 +18,26 @@ If you installed `ESLint` globally, you have to install lodash3 plugin globally
 # Configuration
 
 Add `plugins` section and specify ESLint-plugin-lodash3 as a plugin.
+You can additionally add settings for the plugin.
+
+### Shared Rule Settings
+
+#### Pragma
+Specifies the name you use for the Lodash variable in your code. Default is `_`.
+
+#### Version
+Specifies the major Lodash Version you are using (default is `4`). 
+If you wish to use this plugin with Lodash v3, change this value to 3.
 
 ```json
 {
-  "plugins": ["lodash3"]
+  "plugins": ["lodash3"],
+  "settings": {
+    "lodash": {
+      "version": 4,
+      "pragma": "_"
+    }
+  }
 }
 ```
 
@@ -39,7 +55,7 @@ Finally, enable all of the rules that you would like to use.
     "lodash3/no-single-chain": 2,
     "lodash3/prefer-reject": [2, 3],
     "lodash3/prefer-filter": [2, 3],
-    "lodash3/no-unnecessary-bind": 2,
+    "lodash3/callback-binding": 2,
     "lodash3/unwrap": 2,
     "lodash3/prefer-compact": 2,
     "lodash3/no-double-unwrap": 2,
@@ -74,7 +90,7 @@ Finally, enable all of the rules that you would like to use.
 * [no-single-chain](docs/rules/no-single-chain.md): Prevent chaining syntax for single method, e.g. `_(x).map().value()`
 * [prefer-reject](docs/rules/prefer-reject.md): Prefer `_.reject` over filter with `!(expression)` or `x.prop1 !== value`
 * [prefer-filter](docs/rules/prefer-filter.md): Prefer `_.filter` over `_.forEach` with an `if` statement inside.
-* [no-unnecessary-bind](docs/rules/no-unnecessary-bind.md): Prefer passing `thisArg` over binding.
+* [callback-binding](docs/rules/callback-binding.md): Use or avoid `thisArg` for Lodash method callbacks, depending on major version.
 * [unwrap](docs/rules/unwrap.md): Prevent chaining without evaluation via `value()` or non-chainable methods like `max()`.,
 * [prefer-compact](docs/rules/prefer-compact.md): Prefer `_.compact` over `_.filter` for only truthy values.
 * [no-double-unwrap](docs/rules/no-double-unwrap.md): Do not use `.value()` on chains that have already ended (e.g. with `max()` or `reduce()`)

docs/rules/callback-binding.md

@@ -0,0 +1,44 @@
+# Callback binding
+
+In Lodash version 3, it was possible to pass an additional parameter to methods that require binding, `thisArg`.
+However, in Lodash 4, this option was removed in favor of regular binding, and still using the old method could cause unexpected results.
+
+## Rule Details
+
+This rule takes no arguments. However, it is affected by the lodash `version` defined in the config's [shared settings for Lodash](/README.md#shared-rule-settings). 
+
+### Lodash Version 4 (default)
+In version 4, the following patterns are considered warnings:
+
+```js
+var r = _.filter(users, function (user) {
+    return user.age > this.age;
+}, this);
+
+var r = _.reduce(numbers, multiply, 1, this);
+```
+
+The following patterns are not considered warnings:
+
+```js
+var r = _.filter(users, function (user) {
+    return user.age > this.age;
+}.bind(this));
+```
+
+### Lodash version 3
+
+In version 3, the following patterns are considered warnings:
+```js
+var r = _.filter(users, function (user) {
+    return user.age > this.age;
+}, this);
+```
+
+The following patterns are not considered warnings:
+
+```js
+var r = _.filter(users, function (user) {
+    return user.age > this.age;
+}.bind(this));
+```

lib/rules/callback-binding.js

@@ -0,0 +1,41 @@
+/**
+ * @fileoverview Rule to disallow the use of a chain for a single method
+ */
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = function (context) {
+    var lodashUtil = require('../util/lodashUtil');
+    var astUtil = require('../util/astUtil');
+    var settingsUtil = require('../util/settingsUtil');
+
+    var lodashPragma = settingsUtil.getLodashPragma(context);
+    var majorVersion = settingsUtil.getMajorVersion(context);
+    var transformerMethods = ['reduce', 'reduceRight', 'transform'];
+
+    function isBound(node) {
+        return node && node.type === 'CallExpression' && astUtil.getMethodName(node) === 'bind' && node.arguments.length === 1;
+    }
+
+    var callExpressionReporters = {
+        3: function (node, iteratee) {
+            if (isBound(iteratee)) {
+                context.report(iteratee.callee.property, 'Unnecessary bind, pass `thisArg` to lodash method instead');
+            }
+        },
+        4: function (node, iteratee) {
+            var isTransformerMethod = transformerMethods.some(lodashUtil.isCallToMethod.bind(null, node));
+            var iterateeIndex = node.arguments.indexOf(iteratee);
+            if ((isTransformerMethod && node.arguments[iterateeIndex + 2]) || (!isTransformerMethod && node.arguments[iterateeIndex + 1])) {
+                context.report(iteratee, 'Do not use Lodash 3 thisArg, use binding instead');
+            }
+        }
+    };
+
+    return {
+        CallExpression: lodashUtil.getLodashMethodVisitor(lodashPragma, callExpressionReporters[majorVersion])
+    };
+};

tests/lib/rules/no-unnecessary-bind.js → tests/lib/rules/callback-binding.js

@@ -4,23 +4,29 @@
 // Requirements
 // ------------------------------------------------------------------------------
 
-var rule = require('../../../lib/rules/no-unnecessary-bind');
+var rule = require('../../../lib/rules/callback-binding');
 var RuleTester = require('eslint').RuleTester;
 
 // ------------------------------------------------------------------------------
 // Tests
 // ------------------------------------------------------------------------------
 
 var ruleTester = new RuleTester();
-var toErrorObject = require('../testUtil/toErrorObject').fromMessage('Unnecessary bind, pass `thisArg` to lodash method instead');
-ruleTester.run('no-unnecessary-bind', rule, {
+var optionsUtil = require('../testUtil/optionsUtil');
+ruleTester.run('callback-binding', rule, {
     valid: [
         'var x = _.map(arr, f)',
         'var r = _.find(themeStyleList, function (themeStyle) { return this.x; }, this);',
         'var r = _.find(arr, function (i) { return this.x; }.bind(this, x));'
-    ],
+    ].map(optionsUtil.fromVersion3).concat([
+        'var x = _.map(arr, f.bind(this))',
+        'var x = _.find(users, function(user) { return user.age > this.age}.bind(this));'
+    ]),
     invalid: [
         'var r = _.find(users, function (user) { return user.age > this.age; }.bind(this));',
         'var r = _.find(users, predicate.bind(this));'
-    ].map(toErrorObject)
+    ].map(optionsUtil.fromVersion3).map(optionsUtil.fromMessage('Unnecessary bind, pass `thisArg` to lodash method instead')).concat([
+        'var t = _.find(users, function(user) { return this.x === user}, this);',
+        'var t = _.reduce(users, func, initial, this);'
+    ].map(optionsUtil.fromMessage('Do not use Lodash 3 thisArg, use binding instead')))
 });