Async-storage doesn't work on tvOS

[lkinasiewicz]

Current behavior

Using the lib on tvOS throws "permission denied" error.

Expected behavior

It is possible to use the lib to store data on tvOS.

Repro steps

Just use the library so that it tries to create directory for its files, e.g.:

AsyncStorage.getAllKeys()
  .then(keys => AsyncStorage.multiRemove(keys))
  .catch(error => console.error('Storage clean failed:', error));

Environment

• Async Storage version: 1.11.0
• React-Native version: 0.61.5
• Platform tested: tvOS 13.4.8 device - could not reproduce in simulator
• Logs/Error that are relevant:
  [Error: Failed to create storage directory.Error Domain=NSCocoaErrorDomain Code=513 "You don't have permission to save the file "RCTAsyncLocalStorage_V1" in the folder "com.org.example"." UserInfo={NSFilePath=/var/mobile/Containers/Data/Application/0E076B5B-F577-4D0B-A4E4-58FF3EDF7B5A/Library/Application Support/com.org.example/RCTAsyncLocalStorage_V1, NSUnderlyingError=0x28205dfe0 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}]

I think the regression is caused by this change: 4e49db6#diff-54c57f4041d9a698ab027d21344b6e63R98

According to https://developer.apple.com/library/archive/documentation/General/Conceptual/AppleTV_PG/index.html#//apple_ref/doc/uid/TP40015241 section Local Storage for Your App Is Limited - on tvOS data should be stored either in NSUserDefaults (which is limited to 500KB on tvOS) or in NSCachesDirectory. I guess async-storage should use the latter.

[krizzu]

Hey @lkinasiewicz,

That's interesting. AsyncStorage used NSCacheDirectory previously for tvOS, but now it's moved to NSApplicationSupportDirectory (more reliable on iOS). NSCacheDirectory can be deleted in case of low memory and I can't find reliable source of where tvOS should keep files.

I'll do bunch of tests later on and probably bring back NSCacheDirectory.

[olafurnsig]

@krizzu any update or temp fix?

[krizzu]

@olafurnsig

Temp fix would be to locally move this conditional check, few lines below. I'll try to test and send PR this week

[olafurnsig]

@krizzu

Still getting this though in the react native console:
WARN Persistent storage is not supported on tvOS, your data may be removed at any point.

[krizzu]

@olafurnsig That's due how tvOS is designed. Pretty much all data stored should be purgeable, hence that's why AsyncStorage stores data in such place (NSCachesDirectory). You can read more in programming guide for tvOS in "Local Storage for Your App Is Limited" section

[olafurnsig]

So to persist, say some authentication token, I would need to save it manually in DefaultPreferences, since AsyncStorage uses the NSCacheDirectory that can be purged at any given moment?