Add support for getStaticProps in pages/404

packages/next/build/index.ts

@@ -549,12 +549,12 @@ export default async function build(dir: string, conf = null): Promise<void> {
           }
 
           if (hasPages404 && page === '/404') {
-            if (!result.isStatic) {
+            if (!result.isStatic && !result.hasStaticProps) {
               throw new Error(PAGES_404_GET_INITIAL_PROPS_ERROR)
             }
             // we need to ensure the 404 lambda is present since we use
             // it when _app has getInitialProps
-            if (customAppGetInitialProps) {
+            if (customAppGetInitialProps && !result.hasStaticProps) {
               staticPages.delete(page)
             }
           }

packages/next/lib/constants.ts

@@ -30,4 +30,4 @@ export const SERVER_PROPS_GET_INIT_PROPS_CONFLICT = `You can not use getInitialP
 
 export const SERVER_PROPS_SSG_CONFLICT = `You can not use getStaticProps with getServerSideProps. To use SSG, please remove getServerSideProps`
 
-export const PAGES_404_GET_INITIAL_PROPS_ERROR = `\`pages/404\` can not have getInitialProps/getServerSideProps/getStaticProps, https://err.sh/zeit/next.js/404-get-initial-props`
+export const PAGES_404_GET_INITIAL_PROPS_ERROR = `\`pages/404\` can not have getInitialProps/getServerSideProps, https://err.sh/zeit/next.js/404-get-initial-props`

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

@@ -418,10 +418,7 @@ export async function renderToHTML(
       renderOpts.nextExport = true
     }
 
-    if (
-      pathname === '/404' &&
-      (hasPageGetInitialProps || getServerSideProps || isSSG)
-    ) {
+    if (pathname === '/404' && (hasPageGetInitialProps || getServerSideProps)) {
       throw new Error(PAGES_404_GET_INITIAL_PROPS_ERROR)
     }
   }

test/integration/404-page-ssg/next.config.js

@@ -0,0 +1 @@
+module.exports = {}

test/integration/404-page-ssg/pages/404.js

@@ -0,0 +1,4 @@
+export const getStaticProps = () => ({ props: { hello: 'world' } })
+
+const page = () => `custom 404 page ${Math.random()}`
+export default page

test/integration/404-page-ssg/pages/_app.js

@@ -0,0 +1,12 @@
+const App = ({ Component, pageProps }) => <Component {...pageProps} />
+
+App.getInitialProps = async ({ Component, ctx }) => {
+  if (Component.getInitialProps) {
+    await Component.getInitialProps(ctx)
+  }
+  return {
+    pageProps: {},
+  }
+}
+
+export default App

test/integration/404-page-ssg/pages/err.js

@@ -0,0 +1,5 @@
+const page = () => 'err page'
+page.getInitialProps = () => {
+  throw new Error('oops')
+}
+export default page

test/integration/404-page-ssg/pages/index.js

@@ -0,0 +1 @@
+export default () => 'hello from index'

test/integration/404-page-ssg/test/index.test.js

@@ -0,0 +1,180 @@
+/* eslint-env jest */
+/* global jasmine */
+import fs from 'fs-extra'
+import { join } from 'path'
+import {
+  killApp,
+  findPort,
+  launchApp,
+  nextStart,
+  nextBuild,
+  renderViaHTTP,
+  fetchViaHTTP,
+} from 'next-test-utils'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
+
+const appDir = join(__dirname, '../')
+const nextConfig = join(appDir, 'next.config.js')
+const gip404Err = /`pages\/404` can not have getInitialProps\/getServerSideProps/
+
+let nextConfigContent
+let stdout
+let stderr
+let buildId
+let appPort
+let app
+
+const runTests = isDev => {
+  it('should respond to 404 correctly', async () => {
+    const res = await fetchViaHTTP(appPort, '/404')
+    expect(res.status).toBe(404)
+    expect(await res.text()).toContain('custom 404 page')
+  })
+
+  it('should render error correctly', async () => {
+    const text = await renderViaHTTP(appPort, '/err')
+    expect(text).toContain(isDev ? 'oops' : 'An unexpected error has occurred')
+  })
+
+  it('should not show an error in the logs for 404 SSG', async () => {
+    await renderViaHTTP(appPort, '/non-existent')
+    expect(stderr).not.toMatch(gip404Err)
+    expect(stdout).not.toMatch(gip404Err)
+  })
+
+  it('should render index page normal', async () => {
+    const html = await renderViaHTTP(appPort, '/')
+    expect(html).toContain('hello from index')
+  })
+
+  if (!isDev) {
+    it('should not revalidate custom 404 page', async () => {
+      const res1 = await renderViaHTTP(appPort, '/non-existent')
+      const res2 = await renderViaHTTP(appPort, '/non-existent')
+      const res3 = await renderViaHTTP(appPort, '/non-existent')
+      const res4 = await renderViaHTTP(appPort, '/non-existent')
+
+      expect(res1 === res2 && res2 === res3 && res3 === res4).toBe(true)
+
+      expect(res1).toContain('custom 404 page')
+    })
+
+    it('should set pages404 in routes-manifest correctly', async () => {
+      const data = await fs.readJSON(join(appDir, '.next/routes-manifest.json'))
+      expect(data.pages404).toBe(true)
+    })
+
+    it('should have 404 page in prerender-manifest', async () => {
+      const data = await fs.readJSON(
+        join(appDir, '.next/prerender-manifest.json')
+      )
+      expect(data.routes['/404']).toEqual({
+        initialRevalidateSeconds: false,
+        srcRoute: null,
+        dataRoute: `/_next/data/${buildId}/404.json`,
+      })
+    })
+  }
+}
+
+describe('404 Page Support SSG', () => {
+  describe('server mode', () => {
+    afterAll(() => killApp(app))
+
+    it('should build successfully', async () => {
+      nextConfigContent = await fs.readFile(nextConfig, 'utf8')
+      const {
+        code,
+        stderr: buildStderr,
+        stdout: buildStdout,
+      } = await nextBuild(appDir, [], {
+        stderr: true,
+        stdout: true,
+      })
+
+      expect(code).toBe(0)
+      expect(buildStderr).not.toMatch(gip404Err)
+      expect(buildStdout).not.toMatch(gip404Err)
+
+      appPort = await findPort()
+      stderr = ''
+      stdout = ''
+
+      app = await nextStart(appDir, appPort, {
+        onStdout(msg) {
+          stdout += msg
+        },
+        onStderr(msg) {
+          stderr += msg
+        },
+      })
+      buildId = await fs.readFile(join(appDir, '.next/BUILD_ID'), 'utf8')
+    })
+
+    runTests()
+  })
+
+  describe('serverless mode', () => {
+    afterAll(async () => {
+      await fs.writeFile(nextConfig, nextConfigContent)
+      await killApp(app)
+    })
+
+    it('should build successfully', async () => {
+      nextConfigContent = await fs.readFile(nextConfig, 'utf8')
+      await fs.writeFile(
+        nextConfig,
+        `
+        module.exports = { target: 'experimental-serverless-trace' }
+      `
+      )
+      const {
+        code,
+        stderr: buildStderr,
+        stdout: buildStdout,
+      } = await nextBuild(appDir, [], {
+        stderr: true,
+        stdout: true,
+      })
+
+      expect(code).toBe(0)
+      expect(buildStderr).not.toMatch(gip404Err)
+      expect(buildStdout).not.toMatch(gip404Err)
+
+      appPort = await findPort()
+      stderr = ''
+      stdout = ''
+      app = await nextStart(appDir, appPort, {
+        onStdout(msg) {
+          stdout += msg
+        },
+        onStderr(msg) {
+          stderr += msg
+        },
+      })
+      buildId = await fs.readFile(join(appDir, '.next/BUILD_ID'), 'utf8')
+    })
+
+    runTests()
+  })
+
+  describe('dev mode', () => {
+    beforeAll(async () => {
+      appPort = await findPort()
+      stderr = ''
+      stdout = ''
+      app = await launchApp(appDir, appPort, {
+        onStdout(msg) {
+          stdout += msg
+        },
+        onStderr(msg) {
+          stderr += msg
+        },
+      })
+    })
+    afterAll(() => killApp(app))
+
+    runTests(true)
+  })
+})

test/integration/404-page/test/index.test.js

@@ -182,7 +182,7 @@ describe('404 Page Support', () => {
     expect(stderr).toMatch(gip404Err)
   })
 
-  it('shows error with getStaticProps in pages/404 build', async () => {
+  it('does not show error with getStaticProps in pages/404 build', async () => {
     await fs.move(pages404, `${pages404}.bak`)
     await fs.writeFile(
       pages404,
@@ -196,11 +196,11 @@ describe('404 Page Support', () => {
     await fs.remove(pages404)
     await fs.move(`${pages404}.bak`, pages404)
 
-    expect(stderr).toMatch(gip404Err)
-    expect(code).toBe(1)
+    expect(stderr).not.toMatch(gip404Err)
+    expect(code).toBe(0)
   })
 
-  it('shows error with getStaticProps in pages/404 dev', async () => {
+  it('does not show error with getStaticProps in pages/404 dev', async () => {
     await fs.move(pages404, `${pages404}.bak`)
     await fs.writeFile(
       pages404,
@@ -226,7 +226,7 @@ describe('404 Page Support', () => {
     await fs.remove(pages404)
     await fs.move(`${pages404}.bak`, pages404)
 
-    expect(stderr).toMatch(gip404Err)
+    expect(stderr).not.toMatch(gip404Err)
   })
 
   it('shows error with getServerSideProps in pages/404 build', async () => {