add prefer-lodash-method and prefer-lodash-typecheck (implements wix-incubator#3)

Author: ganimomer

README.md

@@ -45,7 +45,9 @@ Finally, enable all of the rules that you would like to use.
     "lodash3/prefer-map": 1,
     "lodash3/prefer-wrapper-method": 1,
     "lodash3/prefer-invoke": 1,
-    "lodash3/prefer-thru": 1
+    "lodash3/prefer-thru": 1,
+    "lodash3/prefer-lodash-method": 1,
+    "lodash3/prefer-lodash-typecheck": 1
   }
 }
 ```
@@ -67,6 +69,8 @@ Finally, enable all of the rules that you would like to use.
 * [prefer-wrapper-method](docs/rules/prefer-wrapper-method.md): Prefer using array and string methods in the chain and not the initial value, e.g. `_(str).split(' ')...`
 * [prefer-invoke](docs/rules/prefer-invoke.md): Prefer using `_.invoke` over `_.map` with a method call inside.
 * [prefer-thru](docs/rules/prefer-thru.md): Prefer using `_.prototype.thru` in the chain and not call functions in the initial value, e.g. `_(x).thru(f).map(g)...`
+* [prefer-lodash-method](docs/rules/prefer-lodash-method.md): Prefer using Lodash collection methods (e.g. `_.map`) over native array methods.
+* [prefer-lodash-typecheck](docs/rules/prefer-lodash-typecheck.md): Prefer using `_.is*` methods over `typeof` and `instanceof` checks when applicable.
 
 
 # License

docs/rules/prefer-lodash-method.md

@@ -0,0 +1,34 @@
+# Prefer Lodash method
+
+When using native functions like forEach and map, it's often better to use the Lodash implementation. 
+
+## Rule Details
+
+This rule takes no arguments.
+
+The following patterns are considered warnings:
+
+```js
+
+var b = a.map(f);
+
+if (arr.some(f)) {
+  // ...
+}
+
+```
+
+The following patterns are not considered warnings:
+
+```js
+
+_.map(a, f);
+ 
+ _(arr).map(f).reduce(g);
+
+```
+
+
+## When Not To Use It
+
+If you do not want to enforce using Lodash methods, you should not use this rule.

docs/rules/prefer-lodash-typecheck.md

@@ -0,0 +1,36 @@
+# Prefer Lodash typecheck
+
+Getting the specific type of a variable or expression can be done with `typeof` or `instanceof`. However, it's often more expressive to use the Lodash equivalent function
+
+## Rule Details
+
+This rule takes no arguments.
+
+The following patterns are considered warnings:
+
+```js
+
+if (typeof a === 'number') {
+  // ...
+}
+
+var isNotString = typeof b !== 'string';
+
+var isArray = a instanceof Array;
+
+```
+
+The following patterns are not considered warnings:
+
+```js
+
+var areSameType = typeof a === typeof b;
+ 
+var isCar = truck instanceof Car; 
+
+```
+
+
+## When Not To Use It
+
+If you do not want to enforce using Lodash methods for type checks, you should not use this rule.

lib/rules/prefer-lodash-method.js

@@ -0,0 +1,23 @@
+/**
+ * @fileoverview Rule to check if there's a method in the chain start that can be in the chain
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = function (context) {
+    var lodashUtil = require('../util/lodashUtil');
+    var astUtil = require('../util/astUtil');
+
+    var REPORT_MESSAGE = 'Prefer \'_.{{method}}\' over the native function.';
+
+    return {
+        CallExpression: function (node) {
+            if (!lodashUtil.isLodashCall(node) && !lodashUtil.isLodashWrapper(astUtil.getCaller(node)) && lodashUtil.canBeLodashMethod(astUtil.getMethodName(node))) {
+                context.report(node, REPORT_MESSAGE, {method: astUtil.getMethodName(node)});
+            }
+        }
+    };
+};

lib/rules/prefer-lodash-typecheck.js

@@ -0,0 +1,47 @@
+/**
+ * @fileoverview Rule to check if there's a method in the chain start that can be in the chain
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = function (context) {
+    var lodashUtil = require('../util/lodashUtil');
+
+    function isTypeOf(node) {
+        return node && node.type === 'UnaryExpression' && node.operator === 'typeof';
+    }
+
+    function isLiteral(node) {
+        return node && node.type === 'Literal';
+    }
+
+    function isStrictComparison(node) {
+        return (node.operator === '===' || node.operator === '!==');
+    }
+
+    function isCompareTypeOfToLiteral(node) {
+        return isStrictComparison(node) &&
+            ((isTypeOf(node.left) && isLiteral(node.right)) || (isTypeOf(node.right) && isLiteral(node.left)));
+    }
+
+    var REPORT_MESSAGE = 'Prefer \'_.{{method}}\' over {{actual}}.';
+
+    return {
+        BinaryExpression: function (node) {
+            if (isCompareTypeOfToLiteral(node)) {
+                context.report(node, REPORT_MESSAGE, {
+                    method: lodashUtil.getIsTypeMethod(isLiteral(node.left) ? node.left.value : node.right.value),
+                    actual: '\'typeof\' comparison'
+                });
+            } else if (node.operator === 'instanceof') {
+                var lodashEquivalent = lodashUtil.getIsTypeMethod(node.right.name);
+                if (node.right.type === 'Identifier' && lodashEquivalent) {
+                    context.report(node, REPORT_MESSAGE, {method: lodashEquivalent, actual: '\'instanceof ' + node.right.name + '\''});
+                }
+            }
+        }
+    };
+};

lib/util/lodashUtil.js

@@ -54,7 +54,14 @@ function isCallToMethod(node, method) {
 function isLodashWrapperMethod(node) {
     return _.includes(aliasMap.WRAPPER_METHODS, astUtil.getMethodName(node)) && node.type === 'CallExpression';
 }
+function getIsTypeMethod(name) {
+    var types = ['number', 'boolean', 'function', 'Function', 'string', 'object', 'undefined', 'Date', 'Array', 'Error', 'Element'];
+    return _.includes(types, name) ? 'is' + _.capitalize(name) : null;
+}
 
+function canBeLodashMethod(name) {
+    return _.includes(['forEach', 'map', 'reduce', 'filter', 'every', 'some'], name);
+}
 module.exports = {
     isLodashCall: isLodashCall,
     isLodashChainStart: isLodashChainStart,
@@ -65,5 +72,7 @@ module.exports = {
     isChainBreaker: isChainBreaker,
     isExplicitMethodChaining: isExplicitMethodChaining,
     isCallToMethod: isCallToMethod,
-    isLodashWrapperMethod: isLodashWrapperMethod
+    isLodashWrapperMethod: isLodashWrapperMethod,
+    getIsTypeMethod: getIsTypeMethod,
+    canBeLodashMethod: canBeLodashMethod
 };

tests/lib/rules/prefer-lodash-method.js

@@ -0,0 +1,32 @@
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var rule = require('../../../lib/rules/prefer-lodash-method');
+var RuleTester = require('eslint').RuleTester;
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+var ruleTester = new RuleTester();
+var errors = [{message: 'Prefer \'_.map\' over the native function.'}];
+ruleTester.run('prefer-lodash-method', rule, {
+    valid: [{
+        code: 'var x = _.map(arr, f)'
+    }, {
+        code: 'var x = _(arr).map(f).reduce(g)'
+    }, {
+        code: 'var x = _.chain(arr).map(f).reduce(g).value()'
+    }],
+    invalid: [{
+        code: 'var x = a.map(function(x) {return x.f()});',
+        errors: errors
+    }, {
+        code: 'var x = arr.map(x => x.f())',
+        ecmaFeatures: {arrowFunctions: true},
+        errors: errors
+    }]
+});

tests/lib/rules/prefer-lodash-typecheck.js

@@ -0,0 +1,37 @@
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var rule = require('../../../lib/rules/prefer-lodash-typecheck');
+var RuleTester = require('eslint').RuleTester;
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+var ruleTester = new RuleTester();
+var errors = {
+    typeof: [{message: 'Prefer \'_.isNumber\' over \'typeof\' comparison.'}],
+    instanceof: [{message: 'Prefer \'_.isArray\' over \'instanceof Array\'.'}]
+};
+ruleTester.run('prefer-lodash-typecheck', rule, {
+    valid: [{
+        code: 'var x = a instanceof B'
+    }, {
+        code: 'var x = a > b ? a : b'
+    }, {
+        code: 'var x = typeof a === typeof b'
+    }],
+    invalid: [{
+        code: 'var x = typeof a === "number"',
+        errors: errors.typeof
+    }, {
+        code: 'var x = "number" !== typeof a',
+        errors: errors.typeof
+    }, {
+        code: 'var x = a instanceof Array',
+        errors: errors.instanceof
+    }]
+});