Attach previewData to API Route request (#13373)

Co-authored-by: NJoe Haddad <timer150@gmail.com>
Co-authored-by: NTim Neutkens <timneutkens@me.com>

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

@@ -199,6 +199,12 @@ export interface NextApiRequest extends IncomingMessage {
   body: any
 
   env: Env
+
+  preview?: boolean
+  /**
+   * Preview data set on the request, if any
+   * */
+  previewData?: any
 }
 
 /**

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

@@ -46,7 +46,16 @@ export async function apiResolver(
     setLazyProp({ req: apiReq }, 'cookies', getCookieParser(req))
     // Parsing query string
     setLazyProp({ req: apiReq, params }, 'query', getQueryParser(req))
-    // // Parsing of body
+    // Parsing preview data
+    setLazyProp({ req: apiReq }, 'previewData', () =>
+      tryGetPreviewData(req, res, apiContext)
+    )
+    // Checking if preview mode is enabled
+    setLazyProp({ req: apiReq }, 'preview', () =>
+      apiReq.previewData !== false ? true : undefined
+    )
+
+    // Parsing of body
     if (bodyParser) {
       apiReq.body = await parseBody(
         apiReq,

test/integration/prerender-preview/pages/api/read.js

+export default (req, res) => {
+  const { preview, previewData } = req
+  res.json({
+    preview,
+    previewData,
+  })
+}

test/integration/prerender-preview/test/index.test.js

@@ -182,6 +182,27 @@ function runTests(startServer = nextStart) {
     expect(cookies[1]).not.toHaveProperty('Max-Age')
   })
 
+  it('should pass undefined to API routes when not in preview', async () => {
+    const res = await fetchViaHTTP(appPort, `/api/read`)
+    const json = await res.json()
+
+    expect(json).toMatchObject({})
+  })
+  it('should pass the preview data to API routes', async () => {
+    const res = await fetchViaHTTP(
+      appPort,
+      '/api/read',
+      {},
+      { headers: { Cookie: previewCookieString } }
+    )
+    const json = await res.json()
+
+    expect(json).toMatchObject({
+      preview: true,
+      previewData: { lets: 'goooo' },
+    })
+  })
+
   afterAll(async () => {
     await killApp(app)
   })