Don't convert error to string

packages/next/build/output/log.ts

@@ -10,30 +10,30 @@ export const prefixes = {
   trace: chalk.magenta('trace') + ' -',
 }
 
-export function wait(...message: string[]) {
+export function wait(...message: any[]) {
   console.log(prefixes.wait, ...message)
 }
 
-export function error(...message: string[]) {
+export function error(...message: any[]) {
   console.error(prefixes.error, ...message)
 }
 
-export function warn(...message: string[]) {
+export function warn(...message: any[]) {
   console.warn(prefixes.warn, ...message)
 }
 
-export function ready(...message: string[]) {
+export function ready(...message: any[]) {
   console.log(prefixes.ready, ...message)
 }
 
-export function info(...message: string[]) {
+export function info(...message: any[]) {
   console.log(prefixes.info, ...message)
 }
 
-export function event(...message: string[]) {
+export function event(...message: any[]) {
   console.log(prefixes.event, ...message)
 }
 
-export function trace(...message: string[]) {
+export function trace(...message: any[]) {
   console.log(prefixes.trace, ...message)
 }

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

@@ -693,7 +693,7 @@ export default class DevServer extends Server {
   ) {
     let usedOriginalStack = false
 
-    if (isError(err) && err.name && err.stack && err.message) {
+    if (isError(err) && err.stack) {
       try {
         const frames = parseStack(err.stack!)
         const frame = frames[0]
@@ -751,11 +751,11 @@ export default class DevServer extends Server {
 
     if (!usedOriginalStack) {
       if (type === 'warning') {
-        Log.warn(err + '')
+        Log.warn(err)
       } else if (type) {
-        Log.error(`${type}:`, err + '')
+        Log.error(`${type}:`, err)
       } else {
-        Log.error(err + '')
+        Log.error(err)
       }
     }
   }

test/integration/custom-server/server.js

@@ -18,6 +18,11 @@ app.prepare().then(() => {
       return app.render(req, res, '/no-query')
     }
 
+    if (req.url === '/unhandled-rejection') {
+      Promise.reject(new Error('unhandled rejection'))
+      return res.end('ok')
+    }
+
     if (/setAssetPrefix/.test(req.url)) {
       app.setAssetPrefix(`http://127.0.0.1:${port}`)
     } else if (/setEmptyAssetPrefix/.test(req.url)) {

test/integration/custom-server/test/index.test.js

@@ -216,4 +216,26 @@ describe('Custom Server', () => {
       expect(data).toMatch(/hello world/)
     })
   })
+
+  describe('unhandled rejection', () => {
+    afterEach(() => killApp(server))
+
+    it('stderr should include error message and stack trace', async () => {
+      let stderr = ''
+      await startServer(
+        {},
+        {
+          onStderr(msg) {
+            stderr += msg || ''
+          },
+        }
+      )
+      await fetchViaHTTP(appPort, '/unhandled-rejection')
+      await check(() => stderr, /unhandledRejection/)
+      expect(stderr).toContain(
+        'error - unhandledRejection: Error: unhandled rejection'
+      )
+      expect(stderr).toContain('server.js:22:22')
+    })
+  })
 })

test/integration/server-side-dev-errors/pages/uncaught-empty-exception.js

@@ -0,0 +1,12 @@
+export default function Page() {
+  return <p>getServerSideProps page</p>
+}
+
+export async function getServerSideProps() {
+  setTimeout(() => {
+    throw new Error()
+  }, 10)
+  return {
+    props: {},
+  }
+}

test/integration/server-side-dev-errors/pages/uncaught-empty-rejection.js

@@ -0,0 +1,12 @@
+export default function Page() {
+  return <p>getServerSideProps page</p>
+}
+
+export async function getServerSideProps() {
+  setTimeout(() => {
+    Promise.reject(new Error())
+  }, 10)
+  return {
+    props: {},
+  }
+}

test/integration/server-side-dev-errors/test/index.test.js

@@ -11,6 +11,7 @@ import {
   hasRedbox,
   getRedboxSource,
 } from 'next-test-utils'
+import stripAnsi from 'strip-ansi'
 
 const appDir = join(__dirname, '../')
 const gspPage = join(appDir, 'pages/gsp.js')
@@ -213,6 +214,22 @@ describe('server-side dev errors', () => {
     }, 'success')
   })
 
+  it('should show server-side error for uncaught empty rejection correctly', async () => {
+    const stderrIdx = stderr.length
+    await webdriver(appPort, '/uncaught-empty-rejection')
+
+    await check(async () => {
+      const cleanStderr = stripAnsi(stderr.slice(stderrIdx))
+
+      return cleanStderr.includes('pages/uncaught-empty-rejection.js') &&
+        cleanStderr.includes('7:19') &&
+        cleanStderr.includes('getServerSideProps') &&
+        cleanStderr.includes('new Error()')
+        ? 'success'
+        : cleanStderr
+    }, 'success')
+  })
+
   it('should show server-side error for uncaught exception correctly', async () => {
     const stderrIdx = stderr.length
     await webdriver(appPort, '/uncaught-exception')
@@ -228,4 +245,20 @@ describe('server-side dev errors', () => {
         : err
     }, 'success')
   })
+
+  it('should show server-side error for uncaught empty exception correctly', async () => {
+    const stderrIdx = stderr.length
+    await webdriver(appPort, '/uncaught-empty-exception')
+
+    await check(async () => {
+      const cleanStderr = stripAnsi(stderr.slice(stderrIdx))
+
+      return cleanStderr.includes('pages/uncaught-empty-exception.js') &&
+        cleanStderr.includes('7:10') &&
+        cleanStderr.includes('getServerSideProps') &&
+        cleanStderr.includes('new Error()')
+        ? 'success'
+        : cleanStderr
+    }, 'success')
+  })
 })