SSG Preview Mode

package.json

@@ -40,6 +40,7 @@
     "@babel/preset-react": "7.7.0",
     "@fullhuman/postcss-purgecss": "1.3.0",
     "@mdx-js/loader": "0.18.0",
+    "@types/cheerio": "0.22.16",
     "@types/http-proxy": "1.17.3",
     "@types/jest": "24.0.13",
     "@types/string-hash": "1.1.1",
@@ -59,6 +60,7 @@
     "caniuse-lite": "^1.0.30001019",
     "cheerio": "0.22.0",
     "clone": "2.1.2",
+    "cookie": "0.4.0",
     "coveralls": "3.0.3",
     "cross-env": "6.0.3",
     "cross-spawn": "6.0.5",

packages/next/build/entries.ts

@@ -1,12 +1,12 @@
 import chalk from 'chalk'
 import { join } from 'path'
 import { stringify } from 'querystring'
-
 import { API_ROUTE, DOT_NEXT_ALIAS, PAGES_DIR_ALIAS } from '../lib/constants'
+import { __ApiPreviewProps } from '../next-server/server/api-utils'
 import { isTargetLikeServerless } from '../next-server/server/config'
+import { normalizePagePath } from '../next-server/server/normalize-page-path'
 import { warn } from './output/log'
 import { ServerlessLoaderQuery } from './webpack/loaders/next-serverless-loader'
-import { normalizePagePath } from '../next-server/server/normalize-page-path'
 
 type PagesMapping = {
   [page: string]: string
@@ -63,6 +63,7 @@ export function createEntrypoints(
   pages: PagesMapping,
   target: 'server' | 'serverless' | 'experimental-serverless-trace',
   buildId: string,
+  previewMode: __ApiPreviewProps,
   config: any
 ): Entrypoints {
   const client: WebpackEntrypoints = {}
@@ -88,6 +89,7 @@ export function createEntrypoints(
           serverRuntimeConfig: config.serverRuntimeConfig,
         })
       : '',
+    previewProps: JSON.stringify(previewMode),
   }
 
   Object.keys(pages).forEach(page => {

packages/next/build/index.ts

@@ -1,5 +1,6 @@
 import chalk from 'chalk'
 import ciEnvironment from 'ci-info'
+import crypto from 'crypto'
 import escapeStringRegexp from 'escape-string-regexp'
 import findUp from 'find-up'
 import fs from 'fs'
@@ -41,9 +42,11 @@ import {
   getSortedRoutes,
   isDynamicRoute,
 } from '../next-server/lib/router/utils'
+import { __ApiPreviewProps } from '../next-server/server/api-utils'
 import loadConfig, {
   isTargetLikeServerless,
 } from '../next-server/server/config'
+import { normalizePagePath } from '../next-server/server/normalize-page-path'
 import {
   eventBuildCompleted,
   eventBuildOptimize,
@@ -67,7 +70,6 @@ import {
 } from './utils'
 import getBaseWebpackConfig from './webpack-config'
 import { writeBuildId } from './write-build-id'
-import { normalizePagePath } from '../next-server/server/normalize-page-path'
 
 const fsAccess = promisify(fs.access)
 const fsUnlink = promisify(fs.unlink)
@@ -97,6 +99,7 @@ export type PrerenderManifest = {
   version: number
   routes: { [route: string]: SsgRoute }
   dynamicRoutes: { [route: string]: DynamicSsgRoute }
+  preview: __ApiPreviewProps
 }
 
 export default async function build(dir: string, conf = null): Promise<void> {
@@ -198,8 +201,20 @@ export default async function build(dir: string, conf = null): Promise<void> {
   const allStaticPages = new Set<string>()
   let allPageInfos = new Map<string, PageInfo>()
 
+  const previewProps: __ApiPreviewProps = {
+    previewModeId: crypto.randomBytes(16).toString('hex'),
+    previewModeSigningKey: crypto.randomBytes(32).toString('hex'),
+    previewModeEncryptionKey: crypto.randomBytes(32).toString('hex'),
+  }
+
   const mappedPages = createPagesMapping(pagePaths, config.pageExtensions)
-  const entrypoints = createEntrypoints(mappedPages, target, buildId, config)
+  const entrypoints = createEntrypoints(
+    mappedPages,
+    target,
+    buildId,
+    previewProps,
+    config
+  )
   const pageKeys = Object.keys(mappedPages)
   const dynamicRoutes = pageKeys.filter(page => isDynamicRoute(page))
   const conflictingPublicFiles: string[] = []
@@ -802,6 +817,7 @@ export default async function build(dir: string, conf = null): Promise<void> {
       version: 1,
       routes: finalPrerenderRoutes,
       dynamicRoutes: finalDynamicRoutes,
+      preview: previewProps,
     }
 
     await fsWriteFile(
@@ -814,6 +830,7 @@ export default async function build(dir: string, conf = null): Promise<void> {
       version: 1,
       routes: {},
       dynamicRoutes: {},
+      preview: previewProps,
     }
     await fsWriteFile(
       path.join(distDir, PRERENDER_MANIFEST),

packages/next/build/webpack/loaders/next-serverless-loader.ts

@@ -1,14 +1,16 @@
-import { loader } from 'webpack'
+import devalue from 'devalue'
+import escapeRegexp from 'escape-string-regexp'
 import { join } from 'path'
 import { parse } from 'querystring'
+import { loader } from 'webpack'
+import { API_ROUTE } from '../../../lib/constants'
 import {
   BUILD_MANIFEST,
-  ROUTES_MANIFEST,
   REACT_LOADABLE_MANIFEST,
+  ROUTES_MANIFEST,
 } from '../../../next-server/lib/constants'
 import { isDynamicRoute } from '../../../next-server/lib/router/utils'
-import { API_ROUTE } from '../../../lib/constants'
-import escapeRegexp from 'escape-string-regexp'
+import { __ApiPreviewProps } from '../../../next-server/server/api-utils'
 
 export type ServerlessLoaderQuery = {
   page: string
@@ -23,6 +25,7 @@ export type ServerlessLoaderQuery = {
   canonicalBase: string
   basePath: string
   runtimeConfig: string
+  previewProps: string
 }
 
 const nextServerlessLoader: loader.Loader = function() {
@@ -39,6 +42,7 @@ const nextServerlessLoader: loader.Loader = function() {
     generateEtags,
     basePath,
     runtimeConfig,
+    previewProps,
   }: ServerlessLoaderQuery =
     typeof this.query === 'string' ? parse(this.query.substr(1)) : this.query
 
@@ -52,6 +56,10 @@ const nextServerlessLoader: loader.Loader = function() {
   const escapedBuildId = escapeRegexp(buildId)
   const pageIsDynamicRoute = isDynamicRoute(page)
 
+  const encodedPreviewProps = devalue(
+    JSON.parse(previewProps) as __ApiPreviewProps
+  )
+
   const runtimeConfigImports = runtimeConfig
     ? `
       const { setConfig } = require('next/dist/next-server/lib/runtime-config')
@@ -176,6 +184,7 @@ const nextServerlessLoader: loader.Loader = function() {
             res,
             Object.assign({}, parsedUrl.query, params ),
             resolver,
+            ${encodedPreviewProps},
             onError
           )
         } catch (err) {
@@ -243,6 +252,7 @@ const nextServerlessLoader: loader.Loader = function() {
         buildId: "${buildId}",
         assetPrefix: "${assetPrefix}",
         runtimeConfig: runtimeConfig.publicRuntimeConfig || {},
+        previewProps: ${encodedPreviewProps},
         ..._renderOpts
       }
       let _nextData = false

packages/next/next-server/lib/utils.ts

@@ -2,7 +2,6 @@ import { IncomingMessage, ServerResponse } from 'http'
 import { ParsedUrlQuery } from 'querystring'
 import { ComponentType } from 'react'
 import { format, URLFormatOptions, UrlObject } from 'url'
-
 import { ManifestItem } from '../server/load-components'
 import { NextRouter } from './router/router'
 
@@ -201,6 +200,23 @@ export type NextApiResponse<T = any> = ServerResponse & {
    */
   json: Send<T>
   status: (statusCode: number) => NextApiResponse<T>
+
+  /**
+   * Set preview data for Next.js' prerender mode
+   */
+  setPreviewData: (
+    data: object | string,
+    options?: {
+      /**
+       * Specifies the number (in seconds) for the preview session to last for.
+       * The given number will be converted to an integer by rounding down.
+       * By default, no maximum age is set and the preview session finishes
+       * when the client shuts down (browser is closed).
+       */
+      maxAge?: number
+    }
+  ) => NextApiResponse<T>
+  clearPreviewData: () => NextApiResponse<T>
 }
 
 /**