[build-tools] Stop Argent startup when the session is stopped

.changeset/argent-stop-during-startup.md

@@ -0,0 +1,5 @@
+---
+'@expo/build-tools': patch
+---
+
+Stop an Argent session that is still starting up when it is stopped.

packages/build-tools/src/__tests__/utils/startupWatch.ts

@@ -0,0 +1,22 @@
+import { type watchDeviceRunSessionStartup } from '../../steps/utils/deviceRunSessionStartup';
+import { DeviceRunSessionStoppedError } from '../../steps/utils/remoteDeviceRunSession';
+
+/**
+ * A `watchDeviceRunSessionStartup` stand-in that never polls. A test calls `stop` on the
+ * returned watch (`jest.mocked(watchDeviceRunSessionStartup).mock.results[0].value`) to act like
+ * a Stop request during startup.
+ */
+export function createStartupWatchMock({
+  startup,
+}: Parameters<typeof watchDeviceRunSessionStartup>[0]): ReturnType<
+  typeof watchDeviceRunSessionStartup
+> & { stop: () => void } {
+  const stopped = new DeviceRunSessionStoppedError('Stopped during startup.');
+  return {
+    stopped,
+    stop: () => startup.abort(stopped),
+    isStopped: () => startup.signal.reason === stopped,
+    completeAsync: jest.fn(async () => startup.signal.throwIfAborted()),
+    finishAsync: jest.fn(async () => {}),
+  };
+}