perf: cache successful device readiness checks (#465)

Author: thymikee

src/daemon/__tests__/device-ready.test.ts

@@ -1,6 +1,106 @@
-import { test } from 'vitest';
+import { afterEach, beforeEach, expect, test, vi } from 'vitest';
 import assert from 'node:assert/strict';
-import { parseIosReadyPayload, resolveIosReadyHint } from '../device-ready.ts';
+import { promises as fs } from 'node:fs';
+import type { DeviceInfo } from '../../utils/device.ts';
+
+vi.mock('../../utils/exec.ts', () => ({
+  runCmd: vi.fn(),
+}));
+vi.mock('../../platforms/ios/index.ts', () => ({
+  ensureBootedSimulator: vi.fn(async () => {}),
+}));
+vi.mock('../../platforms/android/devices.ts', () => ({
+  waitForAndroidBoot: vi.fn(async () => {}),
+}));
+
+import { runCmd } from '../../utils/exec.ts';
+import { waitForAndroidBoot } from '../../platforms/android/devices.ts';
+import { ensureBootedSimulator } from '../../platforms/ios/index.ts';
+import { ANDROID_EMULATOR, IOS_DEVICE, IOS_SIMULATOR } from '../../__tests__/test-utils/index.ts';
+import {
+  clearDeviceReadyCacheForTests,
+  DEVICE_READY_CACHE_TTL_MS,
+  ensureDeviceReady,
+  parseIosReadyPayload,
+  resolveIosReadyHint,
+} from '../device-ready.ts';
+
+const mockRunCmd = vi.mocked(runCmd);
+const mockEnsureBootedSimulator = vi.mocked(ensureBootedSimulator);
+const mockWaitForAndroidBoot = vi.mocked(waitForAndroidBoot);
+
+beforeEach(() => {
+  vi.useFakeTimers();
+  vi.setSystemTime(new Date('2026-04-01T10:00:00.000Z'));
+  clearDeviceReadyCacheForTests();
+  mockRunCmd.mockReset();
+  mockEnsureBootedSimulator.mockReset();
+  mockEnsureBootedSimulator.mockResolvedValue(undefined);
+  mockWaitForAndroidBoot.mockReset();
+  mockWaitForAndroidBoot.mockResolvedValue(undefined);
+});
+
+afterEach(() => {
+  clearDeviceReadyCacheForTests();
+  vi.useRealTimers();
+});
+
+test('ensureDeviceReady caches successful simulator readiness checks', async () => {
+  const device: DeviceInfo = { ...IOS_SIMULATOR, simulatorSetPath: '/tmp/simset-a' };
+
+  await ensureDeviceReady(device);
+  await ensureDeviceReady({ ...device });
+
+  expect(mockEnsureBootedSimulator).toHaveBeenCalledTimes(1);
+});
+
+test('ensureDeviceReady caches successful iOS physical device readiness checks', async () => {
+  mockRunCmd.mockImplementation(async (_cmd, args) => {
+    const jsonPath = args[args.indexOf('--json-output') + 1];
+    await fs.writeFile(
+      jsonPath,
+      JSON.stringify({
+        result: {
+          connectionProperties: {
+            tunnelState: 'connected',
+          },
+        },
+      }),
+    );
+    return { stdout: '', stderr: '', exitCode: 0 };
+  });
+
+  await ensureDeviceReady(IOS_DEVICE);
+  await ensureDeviceReady({ ...IOS_DEVICE, simulatorSetPath: '/ignored-for-physical-device' });
+
+  expect(mockRunCmd).toHaveBeenCalledTimes(1);
+});
+
+test('ensureDeviceReady includes simulator set path in the cache key', async () => {
+  await ensureDeviceReady({ ...IOS_SIMULATOR, simulatorSetPath: '/tmp/simset-a' });
+  await ensureDeviceReady({ ...IOS_SIMULATOR, simulatorSetPath: '/tmp/simset-b' });
+
+  expect(mockEnsureBootedSimulator).toHaveBeenCalledTimes(2);
+});
+
+test('ensureDeviceReady expires cached readiness checks after the ttl', async () => {
+  await ensureDeviceReady(ANDROID_EMULATOR);
+  vi.setSystemTime(new Date(Date.now() + DEVICE_READY_CACHE_TTL_MS - 1));
+  await ensureDeviceReady({ ...ANDROID_EMULATOR });
+  vi.setSystemTime(new Date(Date.now() + 1));
+  await ensureDeviceReady({ ...ANDROID_EMULATOR });
+
+  expect(mockWaitForAndroidBoot).toHaveBeenCalledTimes(2);
+});
+
+test('ensureDeviceReady does not cache failed readiness checks', async () => {
+  mockEnsureBootedSimulator.mockRejectedValueOnce(new Error('boot failed'));
+
+  await expect(ensureDeviceReady(IOS_SIMULATOR)).rejects.toThrow('boot failed');
+  await ensureDeviceReady(IOS_SIMULATOR);
+
+  expect(mockEnsureBootedSimulator).toHaveBeenCalledTimes(2);
+});
 
 test('parseIosReadyPayload reads tunnelState from direct connectionProperties', () => {
   const parsed = parseIosReadyPayload({

src/daemon/device-ready.ts

@@ -14,24 +14,61 @@ const IOS_DEVICE_READY_TIMEOUT_MS = resolveTimeoutMs(
 );
 const IOS_DEVICE_READY_COMMAND_TIMEOUT_BUFFER_MS = 3_000;
 
+// Exported so unit tests can assert TTL behavior without duplicating the value.
+export const DEVICE_READY_CACHE_TTL_MS = 5_000;
+
+const readyCache = new Map<string, number>();
+
 export async function ensureDeviceReady(device: DeviceInfo): Promise<void> {
+  const cacheKey = deviceReadyCacheKey(device);
+  const cachedUntil = readyCache.get(cacheKey);
+  if (cachedUntil !== undefined) {
+    if (cachedUntil > Date.now()) {
+      return;
+    }
+    readyCache.delete(cacheKey);
+  }
+
   if (device.platform === 'ios') {
     if (device.kind === 'simulator') {
       const { ensureBootedSimulator } = await import('../platforms/ios/index.ts');
       await ensureBootedSimulator(device);
+      markDeviceReady(cacheKey);
       return;
     }
     if (device.kind === 'device') {
       await ensureIosDeviceReady(device.id);
+      markDeviceReady(cacheKey);
       return;
     }
   }
   if (device.platform === 'android') {
     const { waitForAndroidBoot } = await import('../platforms/android/devices.ts');
     await waitForAndroidBoot(device.id);
+    markDeviceReady(cacheKey);
   }
 }
 
+// Test-only reset hook for this daemon-local cache.
+export function clearDeviceReadyCacheForTests(): void {
+  readyCache.clear();
+}
+
+function markDeviceReady(cacheKey: string): void {
+  readyCache.set(cacheKey, Date.now() + DEVICE_READY_CACHE_TTL_MS);
+}
+
+function deviceReadyCacheKey(device: DeviceInfo): string {
+  const simulatorSetPath = device.kind === 'simulator' ? (device.simulatorSetPath ?? '') : '';
+  return JSON.stringify([
+    device.platform,
+    device.kind,
+    device.id,
+    device.target ?? '',
+    simulatorSetPath,
+  ]);
+}
+
 async function ensureIosDeviceReady(deviceId: string): Promise<void> {
   const jsonPath = path.join(
     os.tmpdir(),