[eslint config] [base] [breaking] Enforce proper generator star spacing.

Fixes #887.

README.md

@@ -1219,6 +1219,50 @@ Other Style Guides
 
     > Why? They don't transpile well to ES5.
 
+  <a name="generators--spacing"></a>
+  - [11.3](#generators--spacing) If you must use generators, or if you disregard [our advice](#generators--nope), make sure their function signature is spaced properly. eslint: [`generator-star-spacing`](http://eslint.org/docs/rules/generator-star-spacing)
+
+    > Why? `function` and `*` are part of the same conceptual keyword - `*` is not a modifier for `function`, `function*` is a unique construct, different from `function`.
+
+    ```js
+    // bad
+    function * foo() {
+    }
+
+    const bar = function * () {
+    }
+
+    const baz = function *() {
+    }
+
+    const quux = function*() {
+    }
+
+    function*foo() {
+    }
+
+    function *foo() {
+    }
+
+    // very bad
+    function
+    *
+    foo() {
+    }
+
+    const wat = function
+    *
+    () {
+    }
+
+    // good
+    function* foo() {
+    }
+
+    const foo = function* () {
+    }
+    ```
+
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packages/eslint-config-airbnb-base/rules/es6.js

@@ -27,7 +27,8 @@ module.exports = {
     'constructor-super': 0,
 
     // enforce the spacing around the * in generator functions
-    'generator-star-spacing': 0,
+    // http://eslint.org/docs/rules/generator-star-spacing
+    'generator-star-spacing': [2, { 'before': false, 'after': true }],
 
     // disallow modifying variables of class declarations
     // http://eslint.org/docs/rules/no-class-assign