feat(transform): transform react-router imports

Author: ZauberNerd

.babelrc

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+{
+  "presets": ["es2015"],
+}

.gitignore

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+distribution/
+node_modules/

.npmignore

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+source/
+test/
+node_modules/
+.babelrc
+.gitignore

README.md

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+# babel-plugin-transform-react-router-optimize
+
+The [React Router][0] library exposes all methods on the top level import, but
+allows developers to use imports referencing files directly inside `/lib`,
+which can result in smaller bundle sizes as it doesn't import all of the
+Router's dependencies.
+
+See here for more information: [Minimizing Bundle Size][1].
+
+This plugin can be added to your `.babelrc` file and automatically transform
+ES2015 imports to their size optimized counterpart.
+
+## Example
+**In**
+```javascript
+import { Route, IndexRoute } from 'react-router';
+```
+
+**Out**
+```javascript
+import Route from 'react-router/lib/Route';
+import IndexRoute from 'react-router/lib/IndexRoute';
+```
+
+## Installation
+**Note** This plugin is built for babel 6 and does not work with babel 5.
+```sh
+npm install --save-dev babel-plugin-transform-react-router-optimize
+```
+
+## Usage
+
+### Via `.babelrc` (recommended)
+**.babelrc**
+```json
+{
+  "plugins": ["transform-react-router-optimize"]
+}
+```
+
+### Via CLI
+```sh
+babel --plugins transform-react-router-optimize script.js
+```
+
+### Via Node API
+```javascript
+require('babel-core').transform('code', {
+    plugins: ['transform-react-router-optimize']
+});
+```
+
+## License
+
+MIT
+
+[0]: https://github.com/reactjs/react-router/
+[1]: https://github.com/reactjs/react-router/blob/master/docs/guides/MinimizingBundleSize.md

package.json

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+{
+  "name": "babel-plugin-transform-react-router-optimize",
+  "description": "Babel plugin to optimize the bundle size of projects using react-router.",
+  "version": "1.0.0",
+  "license": "MIT",
+  "main": "distribution/index.js",
+  "scripts": {
+    "clean": "rm -rf distribution",
+    "build": "babel -d distribution source",
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "prepublish": "npm run clean && npm run build"
+  },
+  "author": {
+    "name": "Bjoern Brauer",
+    "email": "zaubernerd@nerdlabs.it"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/nerdlabs/babel-plugin-transform-react-router-optimize.git"
+  },
+  "bugs": {
+    "url": "https://github.com/nerdlabs/babel-plugin-transform-react-router-optimize/issues"
+  },
+  "homepage": "https://github.com/nerdlabs/babel-plugin-transform-react-router-optimize#readme",
+  "keywords": [
+    "babel-plugin",
+    "react-router",
+    "optimization",
+    "minify",
+    "react",
+    "reactjs"
+  ],
+  "devDependencies": {
+    "babel-cli": "^6.10.1",
+    "babel-core": "^6.9.1",
+    "babel-preset-es2015": "^6.9.0"
+  }
+}

source/index.js

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+export default function ({types: t}) {
+	const canReplace = (node) => {
+		return node.specifiers.every((specifier) => {
+			return t.isImportSpecifier(specifier)
+				&& specifier.imported.name !== 'default';
+		});
+	};
+
+	const replace = (specifiers) => {
+		return specifiers.map(({local, imported}) => {
+			return t.importDeclaration(
+				[t.importDefaultSpecifier(t.identifier(local.name))],
+				t.stringLiteral(`react-router/lib/${imported.name}`)
+			);
+		});
+	};
+
+	return {
+		visitor: {
+			ImportDeclaration(path) {
+				if (path.node.source.value === 'react-router') {
+					if (canReplace(path.node)) {
+						path.replaceWithMultiple(replace(path.node.specifiers));
+					}
+				}
+			}
+		}
+	};
+}