test(web): prove Vite never binds a port

apps/web/tests/vite-entry.e2e.ts

@@ -2,11 +2,28 @@
 
 import { fileURLToPath } from 'node:url'
 import { join } from 'node:path'
+import { createServer } from 'node:net'
 import { execa } from 'execa'
 import { describe, expect, it } from 'vitest'
 
 const WEB_ROOT = fileURLToPath(new URL('..', import.meta.url))
 
+/** Reserve an available loopback port, then release it for the child invocation. */
+async function freePort(): Promise<number> {
+  const server = createServer()
+  await new Promise<void>((resolve, reject) => {
+    server.once('error', reject)
+    server.listen(0, '127.0.0.1', resolve)
+  })
+  const address = server.address()
+  if (address === null || typeof address === 'string') throw new Error('port probe returned no address')
+  await new Promise<void>((resolve, reject) => server.close((error) => {
+    if (error === undefined) resolve()
+    else reject(error)
+  }))
+  return address.port
+}
+
 describe('Web development entry', () => {
   it('rejects the package dev alias with the full-host correction', async () => {
     const result = await execa('pnpm', ['run', 'dev'], { cwd: WEB_ROOT, reject: false })
@@ -16,14 +33,24 @@ describe('Web development entry', () => {
   })
 
   it('rejects the standalone Vite server with the full-host correction', async () => {
-    const result = await execa(join(WEB_ROOT, 'node_modules/.bin/vite'), ['--host', '127.0.0.1', '--port', '0'], {
+    const port = await freePort()
+    const result = await execa(join(WEB_ROOT, 'node_modules/.bin/vite'), ['--host', '127.0.0.1', '--port', String(port)], {
       cwd: WEB_ROOT,
       reject: false,
-      timeout: 2_000,
+      timeout: 10_000,
     })
+    expect(result.timedOut).toBe(false)
     expect(result.exitCode).not.toBe(0)
     expect(result.stderr).toContain('apps/web is not a standalone application')
     expect(result.stderr).toContain('dsh web')
     expect(result.stderr).toContain('window.__DSH_BOOT__')
+    await expect(new Promise<void>((resolve, reject) => {
+      const probe = createServer()
+      probe.once('error', reject)
+      probe.listen(port, '127.0.0.1', () => probe.close((error) => {
+        if (error === undefined) resolve()
+        else reject(error)
+      }))
+    })).resolves.toBeUndefined()
   })
 })

apps/web/vite.config.ts

@@ -10,12 +10,11 @@ const STANDALONE_ERROR = 'apps/web is not a standalone application: bare Vite ca
 
 /** Fail before a Vite dev or preview server can expose the boot-manifest-free shell. */
 function rejectStandaloneServe(): Plugin {
-  const reject = (): never => { throw new Error(STANDALONE_ERROR) }
   return {
     name: 'dsh-reject-standalone-web-serve',
-    apply: 'serve',
-    configureServer: reject,
-    configurePreviewServer: reject,
+    config(_config, env) {
+      if (env.command === 'serve') throw new Error(STANDALONE_ERROR)
+    },
   }
 }