Fix Xcode cache errors #175659

okorohelijah · 2025-09-19T15:52:34Z

This PR fixes a race condition that causes intermittent build failures on iOS with errors like no such file or directory. These failures were frequently observed in CI tests running on macOS.

The root cause is that the background wireless device discovery process, which uses devicectl, was not being terminated after a target device was selected. This background process could then delete Xcode's module caches while xcodebuild was actively using them, leading to a build failure.

The fix ensures that the wireless device discovery process is explicitly stopped at all logical exit points of the device discovery flow. This is achieved by calling stopExtendedWirelessDeviceDiscovery() as soon as:

A single specified device is found and validated.
An ephemeral device is chosen.
A user interactively selects a device from a list.
The discovery process concludes in a non-interactive environment (like CI).

This change prevents the devicectl process from running concurrently with the app build, thus resolving the race condition and improving the reliability of iOS builds.

Testing:

This is tested by checking the bringup to make sure the following tests are passing:

fixes #174444

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

gemini-code-assist

Code Review

This pull request correctly addresses a race condition causing intermittent iOS build failures by ensuring the wireless device discovery process is stopped at all logical exit points. The introduction of a stopPolling mechanism and its application throughout the device discovery flow is a solid approach to fixing the problem. My review includes one suggestion to refactor a method for improved code clarity and maintainability.

packages/flutter_tools/lib/src/runner/target_devices.dart

packages/flutter_tools/lib/src/runner/flutter_command.dart

packages/flutter_tools/lib/src/macos/xcdevice.dart

packages/flutter_tools/lib/src/ios/devices.dart

packages/flutter_tools/lib/src/ios/core_devices.dart

vashworth · 2025-09-23T21:48:42Z

We synced offline. Here's a summary:

Okay so here's the current flow for wireless device discovery:

flutter/packages/flutter_tools/lib/src/runner/target_devices.dart

Lines 388 to 395 in 4a04204

    
           void startExtendedWirelessDeviceDiscovery({Duration? deviceDiscoveryTimeout}) { 
        
             if (deviceDiscoveryTimeout == null && _includeWirelessDevices) { 
        
               _wirelessDevicesRefresh ??= _deviceManager.refreshExtendedWirelessDeviceDiscoverers( 
        
                 timeout: DeviceManager.minimumWirelessDeviceDiscoveryTimeout, 
        
               ); 
        
             } 
        
             return; 
        
           }

flutter/packages/flutter_tools/lib/src/device.dart

Lines 215 to 224 in 4a04204

    
             Future<void> refreshExtendedWirelessDeviceDiscoverers({ 
        
               Duration? timeout, 
        
               DeviceDiscoveryFilter? filter, 
        
             }) async { 
        
               await Future.wait<List<Device>>(<Future<List<Device>>>[ 
        
                 for (final DeviceDiscovery discoverer in _platformDiscoverers) 
        
                   if (discoverer.requiresExtendedWirelessDeviceDiscovery) 
        
                     discoverer.discoverDevices(timeout: timeout), 
        
               ]); 
        
             }

flutter/packages/flutter_tools/lib/src/device.dart

Lines 516 to 519 in 4a04204

    
             @override 
        
             Future<List<Device>> discoverDevices({Duration? timeout, DeviceDiscoveryFilter? filter}) { 
        
               return _populateDevices(timeout: timeout, filter: filter, resetCache: true); 
        
             }

flutter/packages/flutter_tools/lib/src/device.dart

Lines 526 to 545 in 4a04204

    
             Future<List<Device>> _populateDevices({ 
        
               Duration? timeout, 
        
               DeviceDiscoveryFilter? filter, 
        
               bool resetCache = false, 
        
             }) async { 
        
               if (!deviceNotifier.isPopulated || resetCache) { 
        
                 final List<Device> devices = await pollingGetDevices(timeout: timeout); 
        
                 // If the cache was populated while the polling was ongoing, do not 
        
                 // overwrite the cache unless it's explicitly refreshing the cache. 
        
                 if (!deviceNotifier.isPopulated || resetCache) { 
        
                   deviceNotifier.updateWithNewList(devices); 
        
                 } 
        
               } 
        
               // If a filter is provided, filter cache to only return devices matching. 
        
               if (filter != null) { 
        
                 return filter.filterDevices(deviceNotifier.items); 
        
               } 
        
               return deviceNotifier.items; 
        
             }

flutter/packages/flutter_tools/lib/src/ios/devices.dart

Lines 245 to 251 in 4a04204

    
           Future<List<Device>> pollingGetDevices({Duration? timeout}) async { 
        
             if (!_platform.isMacOS) { 
        
               throw UnsupportedError('Control of iOS devices or simulators only supported on macOS.'); 
        
             } 
        
             return xcdevice.getAvailableIOSDevices(timeout: timeout); 
        
           }

flutter/packages/flutter_tools/lib/src/macos/xcdevice.dart

Lines 444 to 462 in 4a04204

    
             Future<List<IOSDevice>> getAvailableIOSDevices({Duration? timeout}) async { 
        
               final List<Object>? allAvailableDevices = await _getAllDevices( 
        
                 timeout: timeout ?? const Duration(seconds: 2), 
        
               ); 
        
               if (allAvailableDevices == null) { 
        
                 return const <IOSDevice>[]; 
        
               } 
        
               final coreDeviceMap = <String, IOSCoreDevice>{}; 
        
               if (_xcode.isDevicectlInstalled) { 
        
                 final List<IOSCoreDevice> coreDevices = await _coreDeviceControl.getCoreDevices(); 
        
                 for (final device in coreDevices) { 
        
                   if (device.udid == null) { 
        
                     continue; 
        
                   } 
        
                   coreDeviceMap[device.udid!] = device; 
        
                 } 
        
               }

We need a solution that cancels "getAvailableIOSDevices", but only for the wireless device discovery. IDE device polling should not be impacted.

One potential solution would be to introduce a new method just for wireless device discovery.

In xcdevice.dart, add a getAvailableIOSDevicesForWirelessDiscovery, which does essentially the same thing as getAvailableIOSDevices, but also uses a Completer that will kill the devicectl process or will return early:

Completer<void>? _cancelCompleter;
 void cancelListDevices() {
   _cancelCompleter?.complete();
 }

 Future<List<IOSDevice>> getAvailableIOSDevicesForWirelessDiscovery({Duration? timeout}) async {
   _cancelCompleter = Completer<void>();
   final Completer<void> cancelCompleter = _cancelCompleter!;

   final List<Object>? allAvailableDevices = await _getAllDevices(
     timeout: timeout ?? const Duration(seconds: 2),
   );

   if (allAvailableDevices == null) {
     return const <IOSDevice>[];
   }

   if (cancelCompleter.isCompleted) {
     return const <IOSDevice>[];
   }

    final coreDeviceMap = <String, IOSCoreDevice>{};
   if (_xcode.isDevicectlInstalled) {
     final Process coreDeviceProcess = await _coreDeviceControl.startGetCoreDevices();
     unawaited(
       cancelCompleter.future.whenComplete(() {
         coreDeviceProcess.kill(); // I'm not sure what happens if you kill a process that is completed, so may need to wrap this in a try catch or something
       }),
     );
     await coreDeviceProcess.exitCode;
     final List<IOSCoreDevice> coreDevices = _coreDeviceControl.getCoreDevicesFromProcess(coreDeviceProcess);
     }

    return parseDevices(allAvailableDevices, coreDeviceMap);
  }

Then in ios/devices.dart, add a flag to pollingGetDevices that indicates it's for the wireless discovery call and call getAvailableIOSDevicesForWirelessDiscovery:

@override
Future<List<Device>> pollingGetDevices({Duration? timeout, bool forWirelessDiscovery = false}) async {
  if (!_platform.isMacOS) {
    throw UnsupportedError('Control of iOS devices or simulators only supported on macOS.');
  }
  if (forWirelessDiscovery) {
    return xcdevice.getAvailableIOSDevicesForWirelessDiscovery(timeout: timeout);
  }
  return xcdevice.getAvailableIOSDevices(timeout: timeout);
}

The forWirelessDiscovery flag would need to be piped through pollingGetDevices, _populateDevices, discoverDevices from refreshExtendedWirelessDeviceDiscoverers in devices.dart:

  Future<void> refreshExtendedWirelessDeviceDiscoverers({
    Duration? timeout,
    DeviceDiscoveryFilter? filter,
  }) async {
    await Future.wait<List<Device>>(<Future<List<Device>>>[
      for (final DeviceDiscovery discoverer in _platformDiscoverers)
        if (discoverer.requiresExtendedWirelessDeviceDiscovery)
          discoverer.discoverDevices(timeout: timeout, forWirelessDiscovery: true),
    ]);
  }

Then could do something like

  void stopExtendedWirelessDeviceDiscoverers() {
    for (final DeviceDiscovery discoverer in _platformDiscoverers) {
      if (discoverer is IOSDevices) {
        discoverer.cancelListDevices();
      }
    }
  }

This PR fixes a race condition that causes intermittent build failures on iOS with errors like no such file or directory. These failures were frequently observed in CI tests running on macOS. The root cause is that the background wireless device discovery process, which uses `devicectl`, was not being terminated after a target device was selected. This background process could then delete Xcode's module caches while `xcodebuild` was actively using them, leading to a build failure. The fix ensures that the wireless device discovery process is explicitly stopped at all logical exit points of the device discovery flow. This is achieved by calling stopExtendedWirelessDeviceDiscovery() as soon as: - A single specified device is found and validated. - An ephemeral device is chosen. - A user interactively selects a device from a list. - The discovery process concludes in a non-interactive environment (like CI). This change prevents the devicectl process from running concurrently with the app build, thus resolving the race condition and improving the reliability of iOS builds. ### Testing: - This is tested by checking the bringup to make sure the following tests are passing: * [Mac_arm64_ios integration_test_test_ios](https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_arm64_ios%20integration_test_test_ios?limit=200) * [Mac_ios wide_gamut_ios](https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20wide_gamut_ios?limit=200) * [Mac_ios native_assets_ios](https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20native_assets_ios?limit=200) * [Mac_ios spell_check_test](https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20spell_check_test?limit=200) * [Mac_ios channels_integration_test_ios](https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20channels_integration_test_ios?limit=200) fixes flutter#174444 ## Pre-launch Checklist - [X] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [X] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [X] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [X] I signed the [CLA]. - [X] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [X] I added new tests to check the change I am making, or this PR is [test-exempt]. - [ ] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [X] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

Fix Xcode cache errors

b42d367

github-actions bot added the tool Affects the "flutter" command-line tool. See also t: labels. label Sep 19, 2025

okorohelijah requested a review from vashworth September 19, 2025 15:52

gemini-code-assist bot reviewed Sep 19, 2025

View reviewed changes

okorohelijah added 2 commits September 19, 2025 09:01

update FakeDeviceManager

f08e5b0

add test

40d2d5d

flutter deleted a comment from flutter-dashboard bot Sep 19, 2025

improve logic

e5cf564

okorohelijah requested a review from a team as a code owner September 22, 2025 18:18

github-actions bot added platform-ios iOS applications specifically a: desktop Running on desktop team-ios Owned by iOS platform team labels Sep 22, 2025

okorohelijah added 7 commits September 22, 2025 11:33

add test

41f5e26

fix

f6453f3

Merge branch 'master' into fix_174444

a9f1762

fix

23fd807

fix syntax

dacbd9e

Merge branch 'master' into fix_174444

30e5ab5

trigger checks

9c101b7

okorohelijah mentioned this pull request Sep 22, 2025

ci yaml check is stuck on my pr #175814

Closed

4 tasks

vashworth requested changes Sep 23, 2025

View reviewed changes

okorohelijah added 2 commits September 26, 2025 10:02

improve logic

f31a3a6

fix

c32e13f

okorohelijah requested a review from a team as a code owner September 29, 2025 17:34

github-actions bot added the team-android Owned by Android platform team label Sep 29, 2025

okorohelijah added 4 commits September 29, 2025 10:49

Merge branch 'master' into fix_174444

0dbfa7f

fix

9a9b10c

fix

6165b42

fix

7a09683

engine-flutter-autoroll mentioned this pull request Oct 11, 2025

Roll Flutter from e11e2c11288b to 255b46490ada (57 revisions) flutter/packages#10212

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 11, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

6c717e6

engine-flutter-autoroll mentioned this pull request Oct 11, 2025

Roll Flutter from e11e2c11288b to 255b46490ada (57 revisions) flutter/packages#10214

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 11, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

ab1404c

engine-flutter-autoroll mentioned this pull request Oct 12, 2025

Roll Flutter from e11e2c11288b to 255b46490ada (57 revisions) flutter/packages#10216

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 12, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

add6dad

engine-flutter-autoroll mentioned this pull request Oct 12, 2025

Roll Flutter from e11e2c11288b to 04ccef31019b (58 revisions) flutter/packages#10217

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 12, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

f51c3e8

engine-flutter-autoroll mentioned this pull request Oct 12, 2025

Roll Flutter from e11e2c11288b to 04ccef31019b (58 revisions) flutter/packages#10218

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 12, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

2b457c9

engine-flutter-autoroll mentioned this pull request Oct 13, 2025

Roll Flutter from e11e2c11288b to 0205d4e8cc24 (59 revisions) flutter/packages#10222

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 13, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

0e61a63

engine-flutter-autoroll mentioned this pull request Oct 13, 2025

Roll Flutter from e11e2c11288b to aed8fecfdd66 (60 revisions) flutter/packages#10223

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 13, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

fbdb956

engine-flutter-autoroll mentioned this pull request Oct 13, 2025

Roll Flutter from e11e2c11288b to c7fc71ec6829 (61 revisions) flutter/packages#10224

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 13, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

c2d85fa

engine-flutter-autoroll mentioned this pull request Oct 14, 2025

Roll Flutter from e11e2c11288b to c63c6b08a711 (69 revisions) flutter/packages#10225

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

59c0b7a

engine-flutter-autoroll mentioned this pull request Oct 14, 2025

Roll Flutter from e11e2c11288b to 55712c460fb8 (71 revisions) flutter/packages#10226

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

06e2063

engine-flutter-autoroll mentioned this pull request Oct 14, 2025

Roll Flutter from e11e2c11288b to 48d5d48b5d90 (72 revisions) flutter/packages#10227

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

c7bf895

engine-flutter-autoroll mentioned this pull request Oct 14, 2025

Roll Flutter from e11e2c11288b to 7cd821c21093 (73 revisions) flutter/packages#10228

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

46b1f22

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

e514a6f

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 14, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

32990be

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 15, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

5f878b3

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Oct 15, 2025

e04f0bcfc Fix Xcode cache errors (flutter/flutter#175659)

33ba522

vashworth mentioned this pull request Nov 17, 2025

Xcode DerivedData causes unexpected behavior in Flutter project after adding the new iPhone 16e simulator #163845

Closed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Fix Xcode cache errors #175659

Fix Xcode cache errors #175659

okorohelijah commented Sep 19, 2025 •

edited

Loading

Uh oh!

gemini-code-assist bot left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

vashworth commented Sep 23, 2025 •

edited

Loading

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Fix Xcode cache errors #175659

Fix Xcode cache errors #175659

Conversation

okorohelijah commented Sep 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Testing:

Pre-launch Checklist

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

vashworth commented Sep 23, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

okorohelijah commented Sep 19, 2025 •

edited

Loading

vashworth commented Sep 23, 2025 •

edited

Loading