Pass through arguments of the next cli correctly (#6327)

Arguments that held the same name as one of the default commands were filtered out, causing issues.

For example `next build build` would get rid of the second `build` parameter.

Fixes #6263

packages/next/bin/next.ts

@@ -42,7 +42,7 @@ if (args['--version']) {
 }
 
 // Check if we are running `next <subcommand>` or `next`
-const foundCommand = args._.find((cmd) => commands.includes(cmd))
+const foundCommand = commands.includes(args._[0])
 
 // Makes sure the `next <subcommand> --help` case is covered
 // This help message is only showed for `next --help`
@@ -73,8 +73,8 @@ if (args['--inspect']) {
   nodeArguments.push('--inspect')
 }
 
-const command = foundCommand || defaultCommand
-const forwardedArgs = args._.filter((arg) => arg !== command)
+const command = foundCommand ? args._[0] : defaultCommand
+const forwardedArgs = foundCommand ? args._.slice(1) : args._
 
 // Make sure the `next <subcommand> --help` case is covered
 if (args['--help']) {

test/integration/production-build-dir/build/pages/index.js

@@ -0,0 +1 @@
+export default () => <div>Hello World</div>

test/integration/production-build-dir/test/index.test.js

@@ -0,0 +1,69 @@
+/* eslint-env jest */
+/* global jasmine */
+import { dirname, join } from 'path'
+import {
+  nextServer,
+  startApp,
+  stopApp,
+  renderViaHTTP
+} from 'next-test-utils'
+import spawn from 'cross-spawn'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 5
+
+function runNextCommand (argv, options = {}) {
+  return new Promise((resolve, reject) => {
+    console.log(`Running command "next ${argv.join(' ')}"`)
+    const instance = spawn('node', [join(dirname(require.resolve('next/package')), 'dist/bin/next'), ...argv], { ...options.spawnOptions, cwd: join(__dirname, '..'), stdio: ['ignore', 'pipe', 'pipe'] })
+
+    let stderrOutput = ''
+    if (options.stderr) {
+      instance.stderr.on('data', function (chunk) {
+        stderrOutput += chunk
+      })
+    }
+
+    let stdoutOutput = ''
+    if (options.stdout) {
+      instance.stdout.on('data', function (chunk) {
+        stdoutOutput += chunk
+      })
+    }
+
+    instance.on('close', () => {
+      resolve({
+        stdout: stdoutOutput,
+        stderr: stderrOutput
+      })
+    })
+
+    instance.on('error', (err) => {
+      err.stdout = stdoutOutput
+      err.stderr = stderrOutput
+      reject(err)
+    })
+  })
+}
+
+describe('Production Custom Build Directory', () => {
+  describe('With basic usage', () => {
+    it('should render the page', async () => {
+      const result = await runNextCommand(['build', 'build'], {stdout: true, stderr: true})
+      expect(result.stderr).toBe('')
+
+      const app = nextServer({
+        dir: join(__dirname, '../build'),
+        dev: false,
+        quiet: true
+      })
+
+      const server = await startApp(app)
+      const appPort = server.address().port
+
+      const html = await renderViaHTTP(appPort, '/')
+      expect(html).toMatch(/Hello World/)
+
+      await stopApp(server)
+    })
+  })
+})