[refactor] poweredByHeader (#3716) (#3807)

This reverts `fb7c862` per @timneutkens

- Removes the errors/*.md associated
- Puts back `poweredByHeader` for `next.config.js`
- Reincorporates test:

X-Powered-By header
    ✓ should set it by default (3ms)
    ✓ should not set it when poweredByHeader==false (5ms)

Also tested with `yarn link` and verified.

errors/powered-by-header-option-removed.md

@@ -1,15 +0,0 @@
-# The poweredByHeader has been removed
-
-#### Why This Error Occurred
-
-Starting at Next.js version 5.0.0 the `poweredByHeader` option has been removed.
-
-#### Possible Ways to Fix It
-
-If you still want to remove `x-powered-by` you can use one of the custom-server examples.
-
-And then manually remove the header using `res.removeHeader('x-powered-by')`
-
-### Useful Links
-
-- [Custom Server documentation + examples](https://github.com/zeit/next.js#custom-server-and-routing)

server/config.js

@@ -5,6 +5,7 @@ const cache = new Map()
 const defaultConfig = {
   webpack: null,
   webpackDevMiddleware: null,
+  poweredByHeader: true,
   distDir: '.next',
   assetPrefix: '',
   configOrigin: 'default',
@@ -33,9 +34,6 @@ function loadConfig (dir, customConfig) {
   if (path && path.length) {
     const userConfigModule = require(path)
     userConfig = userConfigModule.default || userConfigModule
-    if (userConfig.poweredByHeader === true || userConfig.poweredByHeader === false) {
-      console.warn('> the `poweredByHeader` option has been removed https://err.sh/zeit/next.js/powered-by-header-option-removed')
-    }
     userConfig.configOrigin = 'next.config.js'
   }
 

server/index.js

@@ -323,7 +323,9 @@ export default class Server {
       return
     }
 
-    res.setHeader('X-Powered-By', `Next.js ${pkg.version}`)
+    if (this.config.poweredByHeader) {
+      res.setHeader('X-Powered-By', `Next.js ${pkg.version}`)
+    }
     return sendHTML(req, res, html, req.method, this.renderOpts)
   }
 

test/integration/production/test/index.test.js

@@ -134,6 +134,26 @@ describe('Production Usage', () => {
       await app.render(req, res, req.url)
       expect(headers['X-Powered-By']).toEqual(`Next.js ${pkg.version}`)
     })
+
+    it('should not set it when poweredByHeader==false', async () => {
+      const req = { url: '/stateless', headers: {} }
+      const originalConfigValue = app.config.poweredByHeader
+      app.config.poweredByHeader = false
+      const res = {
+        getHeader () {
+          return false
+        },
+        setHeader (key, value) {
+          if (key === 'XPoweredBy') {
+            throw new Error('Should not set the XPoweredBy header')
+          }
+        },
+        end () {}
+      }
+
+      await app.render(req, res, req.url)
+      app.config.poweredByHeader = originalConfigValue
+    })
   })
 
   dynamicImportTests(context, (p, q) => renderViaHTTP(context.appPort, p, q))