Update to merge props from GSSP methods with _app pageProps (#11709)

* Add warning for pageProps GSSP conflict

* Update warning

* Update to merge pageProps instead of warn on conflict

* bump

* Update merging

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

@@ -584,7 +584,7 @@ export async function renderToHTML(
         data.unstable_revalidate = false
       }
 
-      props.pageProps = data.props
+      props.pageProps = Object.assign({}, props.pageProps, data.props)
       // pass up revalidate and props for export
       // TODO: change this to a different passing mechanism
       ;(renderOpts as any).revalidate = data.unstable_revalidate
@@ -633,7 +633,7 @@ export async function renderToHTML(
         )
       }
 
-      props.pageProps = data.props
+      props.pageProps = Object.assign({}, props.pageProps, data.props)
       ;(renderOpts as any).pageData = props
     }
   } catch (err) {

test/integration/gssp-pageProps-merge/pages/_app.js

@@ -0,0 +1,10 @@
+const App = ({ Component, pageProps }) => <Component {...pageProps} />
+
+App.getInitialProps = () => ({
+  pageProps: {
+    hi: 'override me',
+    hello: 'world',
+  },
+})
+
+export default App

test/integration/gssp-pageProps-merge/pages/gsp.js

@@ -0,0 +1,2 @@
+export const getStaticProps = () => ({ props: { hi: 'hi' } })
+export default props => <p>{JSON.stringify(props)}</p>

test/integration/gssp-pageProps-merge/pages/gssp.js

@@ -0,0 +1,2 @@
+export const getServerSideProps = () => ({ props: { hi: 'hi' } })
+export default props => <p>{JSON.stringify(props)}</p>

test/integration/gssp-pageProps-merge/test/index.test.js

@@ -0,0 +1,81 @@
+/* eslint-env jest */
+/* global jasmine */
+import fs from 'fs-extra'
+import { join } from 'path'
+import cheerio from 'cheerio'
+import {
+  findPort,
+  launchApp,
+  killApp,
+  renderViaHTTP,
+  nextBuild,
+  nextStart,
+} from 'next-test-utils'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
+const appDir = join(__dirname, '..')
+const nextConfig = join(appDir, 'next.config.js')
+
+let appPort
+let app
+
+const runTests = () => {
+  it('should merge _app pageProps and getServerSideProps props', async () => {
+    const html = await renderViaHTTP(appPort, '/gssp')
+    const $ = cheerio.load(html)
+    expect(JSON.parse($('p').text())).toEqual({ hi: 'hi', hello: 'world' })
+  })
+
+  it('should merge _app pageProps and getStaticProps props', async () => {
+    const html = await renderViaHTTP(appPort, '/gsp')
+    const $ = cheerio.load(html)
+    expect(JSON.parse($('p').text())).toEqual({ hi: 'hi', hello: 'world' })
+  })
+}
+
+describe('pageProps GSSP conflict', () => {
+  describe('dev mode', () => {
+    beforeAll(async () => {
+      appPort = await findPort()
+      app = await launchApp(appDir, appPort)
+    })
+    afterAll(() => killApp(app))
+
+    runTests()
+  })
+
+  describe('production mode', () => {
+    beforeAll(async () => {
+      const { code } = await nextBuild(appDir)
+      if (code !== 0) throw new Error(`build failed with code ${code}`)
+
+      appPort = await findPort()
+      app = await nextStart(appDir, appPort)
+    })
+    afterAll(() => killApp(app))
+
+    runTests()
+  })
+
+  describe('serverless mode', () => {
+    beforeAll(async () => {
+      await fs.writeFile(
+        nextConfig,
+        `module.exports = {
+        target: 'experimental-serverless-trace'
+      }`
+      )
+      const { code } = await nextBuild(appDir)
+      if (code !== 0) throw new Error(`build failed with code ${code}`)
+
+      appPort = await findPort()
+      app = await nextStart(appDir, appPort)
+    })
+    afterAll(async () => {
+      await fs.remove(nextConfig)
+      await killApp(app)
+    })
+
+    runTests()
+  })
+})