feat(rules): add 'correct-chaining' rule

Author: alecxe

README.md

@@ -38,6 +38,7 @@ Rule                         | Default       | Options
 ----                         | -------       | ---------
 [missing-perform][]          | 2             |
 [no-browser-pause][]         | 2             |
+[correct-chaining][]         | 2             |
 [missing-wait-message][]     | 1             |
 [no-browser-sleep][]         | 1             |
 [no-by-xpath][]              | 1             |
@@ -93,6 +94,7 @@ See [configuring rules][] for more information.
 [no-expect-in-po]: docs/rules/no-expect-in-po.md
 [no-promise-in-if]: docs/rules/no-promise-in-if.md
 [no-execute-script]: docs/rules/no-execute-script.md
+[correct-chaining]: docs/rules/correct-chaining.md
 [configuring rules]: http://eslint.org/docs/user-guide/configuring#configuring-rules
 
 ## Recommended configuration

docs/rules/correct-chaining.md

@@ -0,0 +1,37 @@
+# Prohibit incorrect chaining of `element` and `element.all`
+
+A rather common mistake can occur when it is needed to [find multiple elements in the context of an element using chaining](https://github.com/angular/protractor/blob/master/docs/locators.md#finding-sub-elements). Example:
+
+```js
+element(by.css('.parent')).element.all(by.css('.child'));
+//    element IS NOT NEEDED^^^^^^^
+```
+
+Correct chaining:
+
+```js
+element(by.css('.parent')).all(by.css('.child'));
+```
+
+**Fixable:** This rule is automatically fixable using the `--fix` flag on the command line.
+
+## Rule details
+
+Any use of the following patterns are considered warnings:
+
+```js
+element(by.css('.parent')).element.all(by.css('.child'));
+$('.parent').element.all(by.css('.child'));
+element.all(by.css('.child')).first().element.all(by.css('.child'));
+$$('.parent').first().element.all(by.css('.child'));
+```
+
+The following patterns are not warnings:
+
+```js
+element(by.css('.parent')).all(by.css('.child'));
+$('.parent').all(by.css('.child'));
+element.all(by.css('.child')).first().all(by.css('.child'));
+$$('.parent').first().all(by.css('.child'));
+element(by.css('.parent')).element(by.css('.child'));
+```

index.js

@@ -19,6 +19,7 @@ var noAbsoluteURL = require('./lib/rules/no-absolute-url')
 var noExpectInPO = require('./lib/rules/no-expect-in-po')
 var noPromiseInIf = require('./lib/rules/no-promise-in-if')
 var noExecuteScript = require('./lib/rules/no-execute-script')
+var correctChaining = require('./lib/rules/correct-chaining')
 
 module.exports = {
   rules: {
@@ -40,13 +41,15 @@ module.exports = {
     'no-absolute-url': noAbsoluteURL,
     'no-expect-in-po': noExpectInPO,
     'no-promise-in-if': noPromiseInIf,
-    'no-execute-script': noExecuteScript
+    'no-execute-script': noExecuteScript,
+    'correct-chaining': correctChaining
   },
   configs: {
     recommended: {
       rules: {
         'protractor/missing-perform': 2,
         'protractor/no-browser-pause': 2,
+        'protractor/correct-chaining': 2,
         'protractor/missing-wait-message': 1,
         'protractor/no-browser-sleep': 1,
         'protractor/no-by-xpath': 1,

lib/rules/correct-chaining.js

@@ -0,0 +1,52 @@
+'use strict'
+
+/**
+ * @fileoverview Prohibit incorrect chaining of `element` and `element.all`
+ * @author Alexander Afanasyev
+ */
+
+module.exports = {
+  meta: {
+    fixable: 'code',
+    schema: []
+  },
+
+  create: function (context) {
+    function isElementAllChained (node) {
+      var property = node.property
+      if (property && property.name === 'element') {
+        var parent = node.parent
+        if (parent && parent.type === 'MemberExpression') {
+          var parentProperty = parent.property
+          return parentProperty && parentProperty.name === 'all'
+        }
+      }
+      return false
+    }
+
+    function createCorrectChainingAutoFixFunction (node) {
+      var property = node.property
+      var startRange = property.range[0] - 1  // -1 to get the "." as well
+      var endRange = property.range[1]
+
+      return function (fixer) {
+        // remove .element from .element.all incorrect chain
+        if (property && property.name === 'element') {  // self-check
+          return fixer.removeRange([startRange, endRange])
+        }
+      }
+    }
+
+    return {
+      MemberExpression: function (node) {
+        if (isElementAllChained(node)) {
+          context.report({
+            node: node,
+            message: 'Incorrect "element" and "element.all" chaining detected',
+            fix: createCorrectChainingAutoFixFunction(node)
+          })
+        }
+      }
+    }
+  }
+}

test/rules/correct-chaining.js

@@ -0,0 +1,58 @@
+'use strict'
+
+var rule = require('../../lib/rules/correct-chaining')
+var RuleTester = require('eslint').RuleTester
+
+var eslintTester = new RuleTester()
+
+eslintTester.run('correct-chaining', rule, {
+  valid: [
+    'element(by.css(".parent")).all(by.css(".child"));',
+    '$(".parent").all(by.css(".child"));',
+    'element.all(by.css(".child")).first().all(by.css(".child"));',
+    '$$(".parent").first().all(by.css(".child"));',
+    'element(by.css(".parent")).element(by.css(".child"));',
+    'element(by.css(".parent"))',
+    'element.all(by.css(".child"))',
+    'element.all(by.css(".parent")).all(by.css(".child"))'
+  ],
+
+  invalid: [
+    {
+      code: 'element(by.css(".parent")).element.all(by.css(".child"));',
+      errors: [
+        {
+          message: 'Incorrect "element" and "element.all" chaining detected'
+        }
+      ],
+      output: 'element(by.css(".parent")).all(by.css(".child"));'
+    },
+    {
+      code: '$(".parent").element.all(by.css(".child"));',
+      errors: [
+        {
+          message: 'Incorrect "element" and "element.all" chaining detected'
+        }
+      ],
+      output: '$(".parent").all(by.css(".child"));'
+    },
+    {
+      code: 'element.all(by.css(".child")).first().element.all(by.css(".child"));',
+      errors: [
+        {
+          message: 'Incorrect "element" and "element.all" chaining detected'
+        }
+      ],
+      output: 'element.all(by.css(".child")).first().all(by.css(".child"));'
+    },
+    {
+      code: '$$(".parent").first().element.all(by.css(".child"));',
+      errors: [
+        {
+          message: 'Incorrect "element" and "element.all" chaining detected'
+        }
+      ],
+      output: '$$(".parent").first().all(by.css(".child"));'
+    }
+  ]
+})