Mock serial console websocket with MSW

app/components/Terminal.tsx

@@ -104,7 +104,11 @@ export default function Terminal({ ws }: TerminalProps) {
 
   return (
     <>
-      <div className="h-full w-[calc(100%-3rem)] text-mono-code" ref={terminalRef} />
+      <div
+        role="application"
+        className="h-full w-[calc(100%-3rem)] text-mono-code"
+        ref={terminalRef}
+      />
       <div className="absolute right-0 top-0 space-y-2 text-default">
         <ScrollButton onClick={() => term?.scrollToTop()} aria-label="Scroll to top">
           <DirectionUpIcon aria-hidden />

app/msw-mock-api.ts

@@ -54,10 +54,17 @@ const randomStatus = () => {
 
 const sleep = async (ms: number) => new Promise((res) => setTimeout(res, ms))
 
+async function streamString(socket: WebSocket, s: string, delayMs = 50) {
+  for (const c of s) {
+    socket.send(c)
+    await sleep(delayMs)
+  }
+}
+
 export async function startMockAPI() {
   // dynamic imports to make extremely sure none of this code ends up in the prod bundle
   const { handlers } = await import('../mock-api/msw/handlers')
-  const { http, HttpResponse } = await import('msw')
+  const { http, HttpResponse, ws } = await import('msw')
   const { setupWorker } = await import('msw/browser')
 
   // defined in here because it depends on the dynamic import
@@ -77,8 +84,27 @@ export async function startMockAPI() {
     // don't return anything means fall through to the real handlers
   })
 
+  // serial console
+  const secure = window.location.protocol === 'https:'
+  const protocol = secure ? 'wss' : 'ws'
+  const serialConsole = `${protocol}://${window.location.host}/v1/instances/:instance/serial-console/stream`
+
   // https://mswjs.io/docs/api/setup-worker/start#options
-  await setupWorker(interceptAll, ...handlers).start({
+  await setupWorker(
+    interceptAll,
+    ...handlers,
+
+    ws.link(serialConsole).addEventListener('connection', async ({ client }) => {
+      client.addEventListener('message', (event) => {
+        // Mirror client messages back (lets you type in the terminal). If it's
+        // an enter key, send a newline.
+        // eslint-disable-next-line @typescript-eslint/no-base-to-string
+        client.send(event.data.toString() === '13' ? '\r\n' : event.data)
+      })
+      await sleep(1000) // make sure everything is ready first (especially a problem in CI)
+      await streamString(client.socket, 'Wake up Neo...')
+    })
+  ).start({
     quiet: true, // don't log successfully handled requests
     // custom handler only to make logging less noisy. unhandled requests still
     // pass through to the server

test/e2e/instance-serial.e2e.ts

@@ -5,7 +5,9 @@
  *
  * Copyright Oxide Computer Company
  */
-import { clickRowAction, expect, test } from './utils'
+import { expect, test, type Page } from '@playwright/test'
+
+import { clickRowAction } from './utils'
 
 test('serial console can connect while starting', async ({ page }) => {
   // create an instance
@@ -29,11 +31,10 @@ test('serial console can connect while starting', async ({ page }) => {
   await expect(page.getByText('The instance is starting')).toBeVisible()
   await expect(page.getByText('The instance is')).toBeHidden()
 
-  // Here it would be nice to test that the serial console connects, but we
-  // can't mock websockets with MSW yet: https://github.com/mswjs/msw/pull/2011
+  await testSerialConsole(page)
 })
 
-test('links in instance actions', async ({ page }) => {
+test('serial console for existing instance', async ({ page }) => {
   await page.goto('/projects/mock-project/instances')
   await clickRowAction(page, 'db1', 'View serial console')
   await expect(page).toHaveURL('/projects/mock-project/instances/db1/serial-console')
@@ -42,4 +43,23 @@ test('links in instance actions', async ({ page }) => {
   await page.getByRole('button', { name: 'Instance actions' }).click()
   await page.getByRole('menuitem', { name: 'View serial console' }).click()
   await expect(page).toHaveURL('/projects/mock-project/instances/db1/serial-console')
+
+  await testSerialConsole(page)
 })
+
+async function testSerialConsole(page: Page) {
+  const xterm = page.getByRole('application')
+
+  // MSW mocks a message. use first() because there are multiple copies on screen
+  await expect(xterm.getByText('Wake up Neo...').first()).toBeVisible()
+
+  // we need to do this for our keypresses to land
+  await page.locator('.xterm-helper-textarea').focus()
+
+  await xterm.pressSequentially('abc')
+  await expect(xterm.getByText('Wake up Neo...abc').first()).toBeVisible()
+  await xterm.press('Enter')
+  await xterm.pressSequentially('def')
+  await expect(xterm.getByText('Wake up Neo...abc').first()).toBeVisible()
+  await expect(xterm.getByText('def').first()).toBeVisible()
+}

vite.config.ts

@@ -134,15 +134,6 @@ export default defineConfig(({ mode }) => ({
           apiMode === 'dogfood' ? `https://${DOGFOOD_HOST}` : 'http://localhost:12220',
         changeOrigin: true,
       },
-      '^/v1/instances/[^/]+/serial-console/stream': {
-        target:
-          // in msw mode, serial console is served by tools/deno/mock-serial-console.ts
-          apiMode === 'dogfood'
-            ? `wss://${DOGFOOD_HOST}`
-            : 'ws://127.0.0.1:' + (apiMode === 'msw' ? 6036 : 12220),
-        changeOrigin: true,
-        ws: true,
-      },
     },
   },
   preview: { headers },