fix(cli-platform-apple): do not re-pass -CurrentDeviceUDID to an already-booted simulator

packages/cli-platform-apple/src/commands/runCommand/__tests__/runOnSimulator.test.ts

@@ -37,11 +37,30 @@ beforeEach(() => {
   );
 });
 
-test('opens Simulator.app with the device UDID when it exists', async () => {
+test('opens Simulator.app with the device UDID when it is not already booted', async () => {
   (fs.existsSync as jest.Mock).mockImplementation((target) =>
     String(target).endsWith('Simulator.app'),
   );
 
+  await runOnSimulator(xcodeProject, 'ios', 'Debug', 'TestApp', args, {
+    ...simulator,
+    state: 'Shutdown',
+  });
+
+  expect(child_process.execFileSync).toHaveBeenCalledWith('open', [
+    `${developerDir}/Applications/Simulator.app`,
+    '--args',
+    '-CurrentDeviceUDID',
+    simulator.udid,
+  ]);
+});
+
+test('opens Simulator.app without -CurrentDeviceUDID when the device is already booted', async () => {
+  (fs.existsSync as jest.Mock).mockImplementation((target) =>
+    String(target).endsWith('Simulator.app'),
+  );
+
+  // `simulator` is already in the `Booted` state.
   await runOnSimulator(
     xcodeProject,
     'ios',
@@ -51,12 +70,16 @@ test('opens Simulator.app with the device UDID when it exists', async () => {
     simulator,
   );
 
+  // Bring the already-running Simulator.app to the foreground without re-issuing
+  // a boot for the booted device, which would otherwise trigger the
+  // "Unable to boot device in current state: Booted" modal alert.
   expect(child_process.execFileSync).toHaveBeenCalledWith('open', [
     `${developerDir}/Applications/Simulator.app`,
-    '--args',
-    '-CurrentDeviceUDID',
-    simulator.udid,
   ]);
+  expect(child_process.execFileSync).not.toHaveBeenCalledWith(
+    'open',
+    expect.arrayContaining(['-CurrentDeviceUDID']),
+  );
 });
 
 test('falls back to DeviceHub via devices:// deep link when Simulator.app is absent', async () => {

packages/cli-platform-apple/src/commands/runCommand/runOnSimulator.ts

@@ -27,8 +27,13 @@ export async function runOnSimulator(
    * that the Simulator.app is running.
    *
    * We also pass it `-CurrentDeviceUDID` so that when we launch it for the first time,
-   * it will not boot the "default" device, but the one we set. If the app is already running,
-   * this flag has no effect.
+   * it will not boot the "default" device, but the one we set.
+   *
+   * We only pass that flag when the target device is not already booted. Passing
+   * `-CurrentDeviceUDID` for an already-booted device makes Simulator.app re-issue a
+   * boot request, which CoreSimulator rejects with "Unable to boot device in current
+   * state: Booted" and surfaces as a modal alert on every subsequent run. When the
+   * device is already booted we just bring the running Simulator.app to the foreground.
    */
   const activeDeveloperDir = child_process
     .execFileSync('xcode-select', ['-p'], {encoding: 'utf8'})
@@ -51,12 +56,12 @@ export async function runOnSimulator(
   );
 
   if (fs.existsSync(simulatorApp)) {
-    child_process.execFileSync('open', [
-      simulatorApp,
-      '--args',
-      '-CurrentDeviceUDID',
-      simulator.udid,
-    ]);
+    child_process.execFileSync(
+      'open',
+      simulator.state === 'Booted'
+        ? [simulatorApp]
+        : [simulatorApp, '--args', '-CurrentDeviceUDID', simulator.udid],
+    );
   } else if (fs.existsSync(deviceHubApp)) {
     child_process.execFileSync('open', [
       `devices://device/open?id=${simulator.udid}`,