Enable import/no-unresolved and import/export rules

These come from eslint-plugin-import. We've been using these rules for a
while at Airbnb so it seems like a good time to include them in this
configuration. We've found the no-unresolved rule in particular to be
very helpful when working across a large codebase.

  https://github.com/benmosher/eslint-plugin-import

Since the no-unresolved rule works on commonjs, I decided to include it
in the node configuration as well.

I think there are some more rules from this plugin that are worth
enabling, but this seems like a great place to start.

packages/eslint-config-airbnb/README.md

@@ -11,23 +11,24 @@ We export three ESLint configurations for your usage.
 ### eslint-config-airbnb
 
 Our default export contains all of our ESLint rules, including EcmaScript 6+
-and React. It requires `eslint`, `eslint-plugin-react`, and `eslint-plugin-jsx-a11y`.
+and React. It requires `eslint`, `eslint-plugin-import`, `eslint-plugin-react`,
+and `eslint-plugin-jsx-a11y`.
 
-1. `npm install --save-dev eslint-config-airbnb eslint-plugin-react eslint-plugin-jsx-a11y eslint`
+1. `npm install --save-dev eslint-config-airbnb eslint-plugin-import eslint-plugin-react eslint-plugin-jsx-a11y eslint`
 2. add `"extends": "airbnb"` to your .eslintrc
 
 ### eslint-config-airbnb/base
 
 Lints ES6+ but does not lint React. Requires `eslint`.
 
-1. `npm install --save-dev eslint-config-airbnb eslint`
+1. `npm install --save-dev eslint-config-airbnb eslint-plugin-import eslint`
 2. add `"extends": "airbnb/base"` to your .eslintrc
 
 ### eslint-config-airbnb/legacy
 
 Lints ES5 and below. Only requires `eslint`.
 
-1. `npm install --save-dev eslint-config-airbnb eslint`
+1. `npm install --save-dev eslint-config-airbnb eslint-plugin-import eslint`
 2. add `"extends": "airbnb/legacy"` to your .eslintrc
 
 See [Airbnb's Javascript styleguide](https://github.com/airbnb/javascript) and

packages/eslint-config-airbnb/package.json

@@ -45,6 +45,7 @@
     "babel-tape-runner": "^1.3.1",
     "eslint": "^2.7.0",
     "eslint-plugin-jsx-a11y": "^0.6.2",
+    "eslint-plugin-import": "^1.4.0",
     "eslint-plugin-react": "^4.3.0",
     "react": "^0.14.8",
     "tape": "^4.5.1",
@@ -53,6 +54,7 @@
   "peerDependencies": {
     "eslint": "^2.7.0",
     "eslint-plugin-jsx-a11y": "^0.6.2",
+    "eslint-plugin-import": "^1.4.0",
     "eslint-plugin-react": "^4.3.0"
   }
 }

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

@@ -11,6 +11,9 @@ module.exports = {
       'objectLiteralDuplicateProperties': false
     }
   },
+  'plugins': [
+    'import'
+  ],
   'rules': {
     // enforces no braces where they can be omitted
     // http://eslint.org/docs/rules/arrow-body-style
@@ -83,6 +86,19 @@ module.exports = {
     'template-curly-spacing': 2,
     // enforce spacing around the * in yield* expressions
     // http://eslint.org/docs/rules/yield-star-spacing
-    'yield-star-spacing': [2, 'after']
+    'yield-star-spacing': [2, 'after'],
+    // disallow invalid exports, e.g. multiple defaults
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/export.md
+    'import/export': 2,
+    // ensure imports point to files/modules that can be resolved
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-unresolved.md
+    'import/no-unresolved': [2, { 'commonjs': true }]
+  },
+  'settings': {
+    'import/resolver': {
+      'node': {
+        'extensions': ['.js', '.json']
+      }
+    }
   }
 };

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

@@ -2,6 +2,9 @@ module.exports = {
   'env': {
     'node': true
   },
+  'plugins': [
+    'import'
+  ],
   'rules': {
     // enforce return after a callback
     'callback-return': 0,
@@ -19,5 +22,15 @@ module.exports = {
     'no-restricted-modules': 0,
     // disallow use of synchronous methods (off by default)
     'no-sync': 0
+    // ensure imports point to files/modules that can be resolved
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-unresolved.md
+    'import/no-unresolved': [2, { 'commonjs': true }],
+  },
+  'settings': {
+    'import/resolver': {
+      'node': {
+        'extensions': ['.js', '.json']
+      }
+    }
   }
 };

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

@@ -166,5 +166,12 @@ module.exports = {
       assignment: true,
       return: true
     }],
+  },
+  'settings': {
+    'import/resolver': {
+      'node': {
+        'extensions': ['.js', '.jsx', '.json']
+      }
+    }
   }
 };