[BUG] v4: File system watching is not supported on this platform (iOS)

[meli27]

Hello! When I run the v4 example on iPad Air 4th gen (iOS 14.5) it returns this

═══════ Exception caught by widgets library ═══════════════════════════════════
The following FileSystemException was thrown building Consumer<GeneralProvider>(dirty, dependencies: [_InheritedProviderScope<GeneralProvider?>]):
File system watching is not supported on this platform, path = ''

The relevant error-causing widget was
Consumer<GeneralProvider> Consumer:[file:///Users/melissavillalobos/Downloads/flutter_map_tile_caching-4/example/lib/pages/home/components/panel/panel.dart:26:16]()
When the exception was thrown, this was the stack
.....

I already added the background_fetch and permission_handler configurations.
I am not sure if I did something wrong , hope someone can help, thanks.

[JaffaKetchup]

Hi there, thanks for your report.
It appears that you haven't done anything wrong on your side, as the example app should be preconfigured.
The panel in that example uses MapCachingManager.watchStoreChanges(), which internally uses .watch() from 'dart:io'. The error would lead me to believe that that method is not supported on iOS, but the official documentation contradicts that:

• Linux: Uses inotify. The implementation supports watching both files and directories. Recursive watching is not supported. Note: When watching files directly, delete events might not happen as expected.
• OS X: Uses FSEvents. The implementation supports watching both files and directories. Recursive watching is supported.

(I'm not sure which iOS comes under, I think it comes under OS X)

I see that you have downloaded the code onto your device. Could you please add some code just to help me debug (I can't test iOS): print() out the parentDirectory.path in use, then send that string on here . You can find this by awaiting MapCachingManager.normalCache, perhaps in the main() method? This would be a huge help, as I can see that the path that it's supposedly watching is empty.

Thanks.

[meli27]

Hello, got it.

Right now is printing this

flutter: [/Users/melissavillalobos/Library/Developer/CoreSimulator/Devices/CCD52F2D-F674-4FBE-A5F3-185408E7C7FB/data/Containers/Data/Application/9011A34B-E6B0-4BF8-85B9-B3B676BA0C8D/Documents/mapCache]()

[JaffaKetchup]

Oops, sorry for that last comment. That was unrelated.
It seems the path is correct, but I'm not sure why the platform support is wrong. I will do some more digging, but (as I said before) I am very limited in my methods to debug iOS. This may be of interest: https://groups.google.com/g/flutter-dev/c/9T4aptRMmqE?

[JaffaKetchup]

I am planning to release whilst this bug is still present. Should it become a big issue, I will try to allocate more hours to solving this, but I am unfortunately quite busy at the moment.
If you have anymore information, please do comment here. Thanks!

[akeblom]

I am getting the same issue.

[JaffaKetchup]

Can you both update to the latest version, and let me know if you now receive another error? Many thanks.

[akeblom]

Yes indeed. Now I get the unsupported error.

[JaffaKetchup]

Unfortunately, this is unresolvable then, as this is not this library's limitation. If you agree with my above comments (that this looks like it could be a bug in Flutter), I'd suggest creating a bug report there and linking here.
Thanks for your reports! If you can donate, please do - Kofi doesn't take a fee!

[meli27]

flutter/flutter#99456