Add default entries to main.js (#1343)

So, we don't need to add them to individual pages.
This also fix the issue where, error pages doesn't ping the server.

Author: arunoda

server/build/webpack.js

@@ -28,15 +28,22 @@ const relativeResolve = rootModuleRelativePath(require)
 export default async function createCompiler (dir, { dev = false, quiet = false, buildDir } = {}) {
   dir = resolve(dir)
   const config = getConfig(dir)
-  const defaultEntries = dev
-    ? [join(__dirname, '..', '..', 'client/webpack-hot-middleware-client')] : []
+  const defaultEntries = dev ? [
+    join(__dirname, '..', '..', 'client', 'webpack-hot-middleware-client'),
+    join(__dirname, '..', '..', 'client', 'on-demand-entries-client')
+  ] : []
   const mainJS = dev
     ? require.resolve('../../client/next-dev') : require.resolve('../../client/next')
 
   let minChunks
 
   const entry = async () => {
-    const entries = { 'main.js': mainJS }
+    const entries = {
+      'main.js': [
+        ...defaultEntries,
+        mainJS
+      ]
+    }
 
     const pages = await glob('pages/**/*.js', { cwd: dir })
     const devPages = pages.filter((p) => p === 'pages/_document.js' || p === 'pages/_error.js')
@@ -45,11 +52,11 @@ export default async function createCompiler (dir, { dev = false, quiet = false,
     // managing pages.
     if (dev) {
       for (const p of devPages) {
-        entries[join('bundles', p)] = [...defaultEntries, `./${p}?entry`]
+        entries[join('bundles', p)] = `./${p}?entry`
       }
     } else {
       for (const p of pages) {
-        entries[join('bundles', p)] = [...defaultEntries, `./${p}?entry`]
+        entries[join('bundles', p)] = `./${p}?entry`
       }
     }
 

server/on-demand-entry-handler.js

@@ -71,11 +71,7 @@ export default function onDemandEntryHandler (devMiddleware, compiler, {
       const pathname = await resolvePath(pagePath)
       const name = join('bundles', pathname.substring(dir.length))
 
-      const entry = [
-        join(__dirname, '..', 'client/webpack-hot-middleware-client'),
-        join(__dirname, '..', 'client', 'on-demand-entries-client'),
-        `${pathname}?entry`
-      ]
+      const entry = `${pathname}?entry`
 
       await new Promise((resolve, reject) => {
         const entryInfo = entries[page]