feat(rules): add 'no-array-finder-methods' rule

README.md

@@ -40,6 +40,7 @@ Rule                         | Default Error Level | Auto-fixable | Options
 [no-browser-pause][]         | 2                   |              |
 [correct-chaining][]         | 2                   | Yes          |
 [no-invalid-selectors][]     | 2                   |              |
+[no-array-finder-methods][]  | 2                   |              |
 [missing-wait-message][]     | 1 (Warning)         |              |
 [no-browser-sleep][]         | 1                   |              |
 [no-by-xpath][]              | 1                   |              |
@@ -106,6 +107,7 @@ See [configuring rules][] for more information.
 [no-angular-attributes]: docs/rules/no-angular-attributes.md
 [no-invalid-selectors]: docs/rules/no-invalid-selectors.md
 [use-promise-all]: docs/rules/use-promise-all.md
+[no-array-finder-methods]: docs/rules/no-array-finder-methods.md
 [configuring rules]: http://eslint.org/docs/user-guide/configuring#configuring-rules
 
 ## Recommended configuration

docs/rules/no-array-finder-methods.md

@@ -0,0 +1,41 @@
+# Disallow using `ElementArrayFinder` methods on `ElementFinder`
+
+This rule is inspired by [this problem](http://stackoverflow.com/questions/39710881/protractor-locator-issues) when `ElementArrayFinder` methods were unintentionally used on `ElementFinder`.
+
+This rule is especially useful if ESLint is configured in your IDE to scan on the fly - you would catch these kinds of problems early.
+
+## Rule details
+
+Here is the current list of methods the rule is looking for:   
+
+    'first', 'last', 'get', 'filter', 'map', 'each', 'reduce', 'count'
+
+Any use of the following patterns are considered warnings:
+
+```js
+element(by.css(".class")).get(0);
+$(".class").first();
+element(by.css(".class")).last();
+element(by.css(".class")).map(function (elm) {});
+$(".class").filter(function (elm) {});
+element(by.css(".class")).each(function (elm) {});
+element(by.css(".class1")).element(by.css(".class2")).first();
+element(by.css(".class1")).$(".class2").first();
+$(".class1").element(by.css(".class2")).first();
+$(".class1").$(".class2").first();
+```
+
+The following patterns are not warnings:
+
+```js
+element.all(by.css(".class")).get(0);
+$$(".class").first();
+element.all(by.css(".class")).last();
+element.all(by.css(".class")).map(function (elm) {});
+$$(".class").filter(function (elm) {});
+element.all(by.css(".class")).each(function (elm) {});
+element(by.css(".class1")).element.all(by.css(".class2")).first();
+element(by.css(".class1")).$$(".class2").first();
+$(".class1").element.all(by.css(".class2")).first();
+$(".class1").$$(".class2").first();
+```

index.js

@@ -26,6 +26,7 @@ var noGetInnerOuterHtml = require('./lib/rules/no-get-inner-outer-html')
 var noAngularAttributes = require('./lib/rules/no-angular-attributes')
 var noInvalidSelectors = require('./lib/rules/no-invalid-selectors')
 var usePromiseAll = require('./lib/rules/use-promise-all')
+var noArrayFinderMethods = require('./lib/rules/no-array-finder-methods')
 
 module.exports = {
   rules: {
@@ -54,7 +55,8 @@ module.exports = {
     'no-get-inner-outer-html': noGetInnerOuterHtml,
     'no-angular-attributes': noAngularAttributes,
     'no-invalid-selectors': noInvalidSelectors,
-    'use-promise-all': usePromiseAll
+    'use-promise-all': usePromiseAll,
+    'no-array-finder-methods': noArrayFinderMethods
   },
   configs: {
     recommended: {
@@ -63,6 +65,7 @@ module.exports = {
         'protractor/no-browser-pause': 2,
         'protractor/correct-chaining': 2,
         'protractor/no-invalid-selectors': 2,
+        'protractor/no-array-finder-methods': 2,
         'protractor/missing-wait-message': 1,
         'protractor/no-browser-sleep': 1,
         'protractor/no-by-xpath': 1,

lib/is-element-finder.js

@@ -0,0 +1,26 @@
+'use strict'
+
+/**
+ * Checks if a given node is an ElementFinder instance.
+ *
+ * @fileoverview Utility function to determine if a node is an ElementFinder
+ * @author Alexander Afanasyev
+ */
+module.exports = function (node) {
+  // handling $ shortcut
+  var callee = node.callee
+  if (callee) {
+    if (callee.name === '$' || callee.name === 'element') {
+      return true
+    }
+
+    // handling $ and element chaining
+    if (callee.type === 'MemberExpression' && callee.property) {
+      if (callee.property.name === '$' || callee.property.name === 'element') {
+        return true
+      }
+    }
+  }
+
+  return false
+}

lib/rules/no-array-finder-methods.js

@@ -0,0 +1,41 @@
+'use strict'
+
+/**
+ * @fileoverview Disallow using `ElementArrayFinder` methods on `ElementFinder`
+ * @author Alexander Afanasyev
+ */
+
+var isElementFinder = require('../is-element-finder')
+var elementArrayFinderMethods = [
+  'first',
+  'last',
+  'get',
+  'filter',
+  'map',
+  'each',
+  'reduce',
+  'count'
+]
+
+module.exports = {
+  meta: {
+    schema: []
+  },
+
+  create: function (context) {
+    return {
+      MemberExpression: function (node) {
+        var property = node.property
+
+        if (property && elementArrayFinderMethods.indexOf(property.name) > -1) {
+          if (isElementFinder(node.object)) {
+            context.report({
+              node: node,
+              message: 'Unexpected "' + property.name + '()" call on ElementFinder'
+            })
+          }
+        }
+      }
+    }
+  }
+}

test/rules/no-array-finder-methods.js

@@ -0,0 +1,104 @@
+'use strict'
+
+var rule = require('../../lib/rules/no-array-finder-methods')
+var RuleTester = require('eslint').RuleTester
+
+var eslintTester = new RuleTester()
+
+eslintTester.run('no-array-finder-methods', rule, {
+  valid: [
+    'element.all(by.css(".class")).get(0);',
+    '$$(".class").first();',
+    'element.all(by.css(".class")).last();',
+    'element.all(by.css(".class")).map(function (elm) {});',
+    '$$(".class").filter(function (elm) {});',
+    'element.all(by.css(".class")).each(function (elm) {});',
+    'element(by.css(".class1")).element.all(by.css(".class2")).first();',
+    'element(by.css(".class1")).$$(".class2").first();',
+    '$(".class1").element.all(by.css(".class2")).first();',
+    '$(".class1").$$(".class2").first();'
+  ],
+
+  invalid: [
+    {
+      code: 'element(by.css(".class")).get(0);',
+      errors: [
+        {
+          message: 'Unexpected "get()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: '$(".class").first();',
+      errors: [
+        {
+          message: 'Unexpected "first()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: 'element(by.css(".class")).last();',
+      errors: [
+        {
+          message: 'Unexpected "last()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: 'element(by.css(".class")).map(function (elm) {});',
+      errors: [
+        {
+          message: 'Unexpected "map()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: '$(".class").filter(function (elm) {});',
+      errors: [
+        {
+          message: 'Unexpected "filter()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: 'element(by.css(".class")).each(function (elm) {});',
+      errors: [
+        {
+          message: 'Unexpected "each()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: 'element(by.css(".class1")).element(by.css(".class2")).first();',
+      errors: [
+        {
+          message: 'Unexpected "first()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: 'element(by.css(".class1")).$(".class2").first();',
+      errors: [
+        {
+          message: 'Unexpected "first()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: '$(".class1").element(by.css(".class2")).first();',
+      errors: [
+        {
+          message: 'Unexpected "first()" call on ElementFinder'
+        }
+      ]
+    },
+    {
+      code: '$(".class1").$(".class2").first();',
+      errors: [
+        {
+          message: 'Unexpected "first()" call on ElementFinder'
+        }
+      ]
+    }
+  ]
+})