Create a babel-preset for plugins and presets we use. (vercel#445)

* Create a babel-preset for plugins and presets we use.
Anyone could get it via 'next/babel'

* Remove  'use strict' from the source.

* Add next/router to alias resolver in our babel preset.

Author: arunoda

babel.js

@@ -0,0 +1 @@
+module.exports = require('./dist/server/build/babel/preset')

server/build/babel.js

@@ -0,0 +1,39 @@
+import { resolve, join, dirname } from 'path'
+import { readFile, writeFile } from 'mz/fs'
+import { transform } from 'babel-core'
+import chokidar from 'chokidar'
+import mkdirp from 'mkdirp-then'
+
+export default babel
+
+async function babel (dir, { dev = false } = {}) {
+  dir = resolve(dir)
+
+  let src
+  try {
+    src = await readFile(join(dir, 'pages', '_document.js'), 'utf8')
+  } catch (err) {
+    if (err.code === 'ENOENT') {
+      src = await readFile(join(__dirname, '..', '..', '..', 'pages', '_document.js'), 'utf8')
+    } else {
+      throw err
+    }
+  }
+
+  const { code } = transform(src, {
+    babelrc: false,
+    sourceMaps: dev ? 'inline' : false,
+    presets: [require.resolve('./preset')]
+  })
+
+  const file = join(dir, '.next', 'dist', 'pages', '_document.js')
+  await mkdirp(dirname(file))
+  await writeFile(file, code)
+}
+
+export function watch (dir) {
+  return chokidar.watch('pages/_document.js', {
+    cwd: dir,
+    ignoreInitial: true
+  })
+}

server/build/babel/index.js

@@ -0,0 +1,34 @@
+const babelRuntimePath = require.resolve('babel-runtime/package')
+  .replace(/[\\/]package\.json$/, '')
+
+module.exports = {
+  presets: [
+    require.resolve('babel-preset-es2015'),
+    require.resolve('babel-preset-react')
+  ],
+  plugins: [
+    require.resolve('babel-plugin-react-require'),
+    require.resolve('babel-plugin-transform-async-to-generator'),
+    require.resolve('babel-plugin-transform-object-rest-spread'),
+    require.resolve('babel-plugin-transform-class-properties'),
+    require.resolve('babel-plugin-transform-runtime'),
+    require.resolve('styled-jsx/babel'),
+    [
+      require.resolve('babel-plugin-module-resolver'),
+      {
+        alias: {
+          'babel-runtime': babelRuntimePath,
+          react: require.resolve('react'),
+          'react-dom': require.resolve('react-dom'),
+          'next/link': require.resolve('../../../lib/link'),
+          'next/prefetch': require.resolve('../../../lib/prefetch'),
+          'next/css': require.resolve('../../../lib/css'),
+          'next/head': require.resolve('../../../lib/head'),
+          'next/document': require.resolve('../../../server/document'),
+          'next/router': require.resolve('../../../server/router'),
+          'styled-jsx/style': require.resolve('styled-jsx/style')
+        }
+      }
+    ]
+  ]
+}

server/build/babel/preset.js

@@ -81,9 +81,6 @@ export default async function createCompiler (dir, { dev = false } = {}) {
     )
   }
 
-  const babelRuntimePath = require.resolve('babel-runtime/package')
-  .replace(/[\\/]package\.json$/, '')
-
   const loaders = (dev ? [{
     test: /\.js(\?[^?]*)?$/,
     loader: 'hot-self-accept-loader',
@@ -137,30 +134,8 @@ export default async function createCompiler (dir, { dev = false } = {}) {
     query: {
       babelrc: false,
       sourceMaps: dev ? 'both' : false,
-      presets: ['es2015', 'react'],
-      plugins: [
-        require.resolve('babel-plugin-react-require'),
-        require.resolve('babel-plugin-transform-async-to-generator'),
-        require.resolve('babel-plugin-transform-object-rest-spread'),
-        require.resolve('babel-plugin-transform-class-properties'),
-        require.resolve('babel-plugin-transform-runtime'),
-        require.resolve('styled-jsx/babel'),
-        [
-          require.resolve('babel-plugin-module-resolver'),
-          {
-            alias: {
-              'babel-runtime': babelRuntimePath,
-              react: require.resolve('react'),
-              'react-dom': require.resolve('react-dom'),
-              'next/link': require.resolve('../../lib/link'),
-              'next/prefetch': require.resolve('../../lib/prefetch'),
-              'next/css': require.resolve('../../lib/css'),
-              'next/head': require.resolve('../../lib/head'),
-              'next/document': require.resolve('../../server/document'),
-              'styled-jsx/style': require.resolve('styled-jsx/style')
-            }
-          }
-        ]
+      presets: [
+        require.resolve('./babel/preset')
       ]
     }
   }])