feat: add type to previewData (vercel#21574)

`previewData` was already [typed declare variable](https://github.com/vercel/next.js/compare/canary...tarunama:feature/remove-any1?expand=1#diff-bd7baf53ff559d84461af8b2fd62cade7e2d8eb203f489e24a27c5b83a79a9d3L1380).
So I have defined `PreviewData` type, and adapt for avoiding error by type safe.

Author: tarunama

errors/invalid-getstaticprops-value.md

@@ -12,7 +12,7 @@ Make sure to return the following shape from `getStaticProps`:
 export async function getStaticProps(ctx: {
   params?: ParsedUrlQuery
   preview?: boolean
-  previewData?: any
+  previewData?: PreviewData
 }) {
   return {
     props: { [key: string]: any }

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

@@ -8,6 +8,7 @@ import { NextRouter } from './router/router'
 import { Env } from '@next/env'
 import { BuildManifest } from '../server/get-page-files'
 import { DomainLocales } from '../server/config'
+import { PreviewData } from 'next/types'
 
 /**
  * Types used by both next and next-server
@@ -220,7 +221,7 @@ export interface NextApiRequest extends IncomingMessage {
   /**
    * Preview data set on the request, if any
    * */
-  previewData?: any
+  previewData?: PreviewData
 }
 
 /**

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

@@ -2,7 +2,7 @@ import { IncomingMessage, ServerResponse } from 'http'
 import { parse } from 'next/dist/compiled/content-type'
 import { CookieSerializeOptions } from 'next/dist/compiled/cookie'
 import getRawBody from 'raw-body'
-import { PageConfig } from 'next/types'
+import { PageConfig, PreviewData } from 'next/types'
 import { Stream } from 'stream'
 import { isResSent, NextApiRequest, NextApiResponse } from '../lib/utils'
 import { decryptWithSecret, encryptWithSecret } from './crypto-utils'
@@ -292,7 +292,7 @@ export function tryGetPreviewData(
   req: IncomingMessage,
   res: ServerResponse,
   options: __ApiPreviewProps
-): object | string | false {
+): PreviewData {
   // Read cached preview data if present
   if (SYMBOL_PREVIEW_DATA in req) {
     return (req as any)[SYMBOL_PREVIEW_DATA] as any

packages/next/next-server/server/next-server.ts

@@ -91,6 +91,7 @@ import { detectDomainLocale } from '../lib/i18n/detect-domain-locale'
 import cookie from 'next/dist/compiled/cookie'
 import escapePathDelimiters from '../lib/router/utils/escape-path-delimiters'
 import { getUtils } from '../../build/webpack/loaders/next-serverless-loader/utils'
+import { PreviewData } from 'next/types'
 
 const getCustomRouteMatcher = pathMatch(true)
 
@@ -1460,7 +1461,7 @@ export default class Server {
     const { i18n } = this.nextConfig
     const locales = i18n?.locales
 
-    let previewData: string | false | object | undefined
+    let previewData: PreviewData
     let isPreviewMode = false
 
     if (hasServerProps || isSSG) {

packages/next/next-server/server/render.tsx

@@ -15,7 +15,7 @@ import {
   UNSTABLE_REVALIDATE_RENAME_ERROR,
 } from '../../lib/constants'
 import { isSerializableProps } from '../../lib/is-serializable-props'
-import { GetServerSideProps, GetStaticProps } from '../../types'
+import { GetServerSideProps, GetStaticProps, PreviewData } from '../../types'
 import { isInAmpMode } from '../lib/amp'
 import { AmpStateContext } from '../lib/amp-context'
 import {
@@ -559,7 +559,7 @@ export async function renderToHTML(
   await Loadable.preloadAll() // Make sure all dynamic imports are loaded
 
   let isPreview
-  let previewData: string | false | object | undefined
+  let previewData: PreviewData
 
   if ((isSSG || getServerSideProps) && !isFallback) {
     // Reads of this are cached on the `req` object, so this should resolve

packages/next/types/index.d.ts

@@ -90,10 +90,12 @@ export {
   NextApiHandler,
 }
 
+export type PreviewData = string | false | object | undefined
+
 export type GetStaticPropsContext<Q extends ParsedUrlQuery = ParsedUrlQuery> = {
   params?: Q
   preview?: boolean
-  previewData?: any
+  previewData?: PreviewData
   locale?: string
   locales?: string[]
   defaultLocale?: string
@@ -141,7 +143,7 @@ export type GetServerSidePropsContext<
   params?: Q
   query: ParsedUrlQuery
   preview?: boolean
-  previewData?: any
+  previewData?: PreviewData
   resolvedUrl: string
   locale?: string
   locales?: string[]