Add new no-get rule

README.md

@@ -89,6 +89,7 @@ The `--fix` option on the command line automatically fixes problems reported by
 | :white_check_mark: | [new-module-imports](./docs/rules/new-module-imports.md) |  Use "New Module Imports" from Ember RFC #176 |
 |  | [no-empty-attrs](./docs/rules/no-empty-attrs.md) | Prevents usage of empty attributes in ember data models |
 | :white_check_mark: | [no-function-prototype-extensions](./docs/rules/no-function-prototype-extensions.md) | Prevents usage of Ember's `function` prototype extensions |
+|  | [no-get](./docs/rules/no-get.md) | Disallow unnecessary usage of Ember's `get` function |
 | :white_check_mark: | [no-global-jquery](./docs/rules/no-global-jquery.md) | Prevents usage of global jQuery object |
 |  | [no-jquery](./docs/rules/no-jquery.md) | Disallow any usage of jQuery |
 |  | [no-new-mixins](./docs/rules/no-new-mixins.md) | Prevents creation of new mixins |

docs/rules/no-get.md

@@ -0,0 +1,44 @@
+# no-get
+
+Starting in Ember 3.1, native ES5 getters are available, which eliminates much of the need to use `get` on Ember objects.
+
+## Rule Details
+
+This rule disallows using `this.get('someProperty')` when `this.someProperty` can be used.
+
+**WARNING**: there are a number of circumstances where `get` still needs to be used, and you may need to manually disable the rule for these:
+
+* Ember proxy objects (`ObjectProxy`, `ArrayProxy`)
+* Objects implementing the `unknownProperty` method
+
+## Examples
+
+Examples of **incorrect** code for this rule:
+
+```js
+const foo = this.get('someProperty');
+```
+
+```js
+import { get } from '@ember/object';
+const foo = get(this, 'someProperty');
+```
+
+Examples of **correct** code for this rule:
+
+
+```js
+const foo = this.someProperty;
+```
+
+```js
+const foo = this.get('some.nested.property'); // Allowed because of nested path.
+```
+
+## References
+
+* [Ember 3.1 Release Notes](https://blog.emberjs.com/2018/04/13/ember-3-1-released.html) describing "ES5 Getters for Computed Properties"
+* [Ember get Spec](https://api.emberjs.com/ember/release/functions/@ember%2Fobject/get)
+* [Ember ES5 Getter RFC](https://github.com/emberjs/rfcs/blob/master/text/0281-es5-getters.md)
+* [es5-getter-ember-codemod](https://github.com/rondale-sc/es5-getter-ember-codemod)
+* [More context](https://github.com/emberjs/ember.js/issues/16148) about the proxy object exception to this rule

lib/index.js

@@ -21,6 +21,7 @@ module.exports = {
     'no-ember-testing-in-module-scope': require('./rules/no-ember-testing-in-module-scope'),
     'no-empty-attrs': require('./rules/no-empty-attrs'),
     'no-function-prototype-extensions': require('./rules/no-function-prototype-extensions'),
+    'no-get': require('./rules/no-get'),
     'no-global-jquery': require('./rules/no-global-jquery'),
     'no-invalid-debug-function-arguments': require('./rules/no-invalid-debug-function-arguments'),
     'no-jquery': require('./rules/no-jquery'),

lib/recommended-rules.js

@@ -23,6 +23,7 @@ module.exports = {
   "ember/no-ember-testing-in-module-scope": "error",
   "ember/no-empty-attrs": "off",
   "ember/no-function-prototype-extensions": "error",
+  "ember/no-get": "off",
   "ember/no-global-jquery": "error",
   "ember/no-invalid-debug-function-arguments": "off",
   "ember/no-jquery": "off",

lib/rules/no-get.js

@@ -0,0 +1,51 @@
+'use strict';
+
+const utils = require('../utils/utils');
+
+function makeErrorMessage(property, isImportedGet) {
+  return isImportedGet
+    ? `Use \`this.${property}\` instead of \`get(this, '${property}')\``
+    : `Use \`this.${property}\` instead of \`this.get('${property}')\``;
+}
+
+module.exports = {
+  makeErrorMessage,
+  meta: {
+    docs: {
+      description: "Disallow unnecessary usage of Ember's `get` function",
+      category: 'Best Practices',
+      recommended: false
+    }
+  },
+  create(context) {
+    return {
+      CallExpression(node) {
+        if (
+          utils.isMemberExpression(node.callee) &&
+          utils.isThisExpression(node.callee.object) &&
+          node.callee.property.name === 'get' &&
+          node.arguments.length === 1 &&
+          utils.isLiteral(node.arguments[0]) &&
+          typeof node.arguments[0].value === 'string' &&
+          !node.arguments[0].value.includes('.')
+        ) {
+          // Example: this.get('foo');
+          context.report(node, makeErrorMessage(node.arguments[0].value), false);
+        }
+
+        if (
+          utils.isIdentifier(node.callee) &&
+          node.callee.name === 'get' &&
+          node.arguments.length === 2 &&
+          utils.isThisExpression(node.arguments[0]) &&
+          utils.isLiteral(node.arguments[1]) &&
+          typeof node.arguments[1].value === 'string' &&
+          !node.arguments[1].value.includes('.')
+        ) {
+          // Example: get(this, 'foo');
+          context.report(node, makeErrorMessage(node.arguments[1].value, true));
+        }
+      }
+    };
+  }
+};

tests/lib/rules/no-get.js

@@ -0,0 +1,46 @@
+const rule = require('../../../lib/rules/no-get');
+const RuleTester = require('eslint').RuleTester;
+
+const { makeErrorMessage } = rule;
+
+const ruleTester = new RuleTester();
+
+ruleTester.run('no-get', rule, {
+  valid: [
+    // Nested property path.
+    "this.get('foo.bar');",
+    "get(this, 'foo.bar');",
+
+    // Not `this`.
+    "foo.get('bar');",
+    "get(foo, 'bar');",
+
+    // Not `get`.
+    "this.foo('bar');",
+    "foo(this, 'bar');",
+
+    // Unknown extra argument.
+    "this.get('foo', 'bar');",
+    "get(this, 'foo', 'bar');",
+
+    // Unexpected argument type.
+    'this.get(5);',
+    'get(this, 5);',
+
+    // Unknown sub-function call:
+    "this.get.foo('bar');",
+    "get.foo(this, 'bar');",
+  ],
+  invalid: [
+    {
+      code: "this.get('foo');",
+      output: null,
+      errors: [{ message: makeErrorMessage('foo', false) }]
+    },
+    {
+      code: "get(this, 'foo');",
+      output: null,
+      errors: [{ message: makeErrorMessage('foo', true) }]
+    }
+  ]
+});