[eslint config] [breaking] add no-duplicate-imports rule.

README.md

@@ -1075,6 +1075,27 @@ Other Style Guides
     export default es6;
     ```
 
+  <a name="modules--no-duplicate-imports"></a>
+  - [10.4](#modules--no-duplicate-imports) Only import from a path in one place.
+ eslint: [`no-duplicate-imports`](http://eslint.org/docs/rules/no-duplicate-imports)
+    > Why? Having multiple lines that import from the same path can make code harder to maintain.
+
+    ```javascript
+    // bad
+    import foo from 'foo';
+    // … some other imports … //
+    import { named1, named2 } from 'foo';
+
+    // good
+    import foo, { named1, named2 } from 'foo';
+
+    // good
+    import foo, {
+      named1,
+      named2,
+    } from 'foo';
+    ```
+
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 ## Iterators and Generators

packages/eslint-config-airbnb/rules/es6.js

@@ -35,6 +35,9 @@ module.exports = {
     }],
     // disallow modifying variables that are declared using const
     'no-const-assign': 2,
+    // disallow importing from the same path more than once
+    // http://eslint.org/docs/rules/no-duplicate-imports
+    'no-duplicate-imports': 2,
     // disallow symbol constructor
     // http://eslint.org/docs/rules/no-new-symbol
     'no-new-symbol': 2,