bug: FileSystem.writeFile crash on Android 11

Bug Report

Thank you all for your great work! I hope you can help me with this problem.

Capacitor Version

  @capacitor/ios not installed
  @capacitor/cli 2.4.6
  @capacitor/android 2.4.6
  @capacitor/core 2.4.6
  @capacitor/electron not installed

Platform(s)

Android

Current Behavior

The bug occurs when I try to write a new file in the Documents folder using the the Filesystem API. In the log an error is thrown complaining the open operation is not permitted.

2021-01-26 08:26:51.896 3598-3598/io.ionic.starter E/Capacitor/Filesystem: Creating text file '/storage/emulated/0/Documents/experiments/26012021/log_08:26:49.csv' with charset 'UTF-8' failed. Error: /storage/emulated/0/Documents/experiments/26012021/log_08:26:49.csv: open failed: EPERM (Operation not permitted)
    java.io.FileNotFoundException: /storage/emulated/0/Documents/experiments/26012021/log_08:26:49.csv: open failed: EPERM (Operation not permitted)
        at libcore.io.IoBridge.open(IoBridge.java:492)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:236)
        at com.getcapacitor.plugin.Filesystem.saveFile(Filesystem.java:269)
        at com.getcapacitor.plugin.Filesystem.writeFile(Filesystem.java:225)
        at com.getcapacitor.plugin.Filesystem.handleRequestPermissionsResult(Filesystem.java:669)
        at com.getcapacitor.Bridge.onRequestPermissionsResult(Bridge.java:763)
        at com.getcapacitor.BridgeActivity.onRequestPermissionsResult(BridgeActivity.java:206)
        at android.app.Activity.dispatchRequestPermissionsResult(Activity.java:8466)
        at android.app.Activity.dispatchActivityResult(Activity.java:8314)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:5008)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5056)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: android.system.ErrnoException: open failed: EPERM (Operation not permitted)
        at libcore.io.Linux.open(Native Method)
        at libcore.io.ForwardingOs.open(ForwardingOs.java:166)
        at libcore.io.BlockGuardOs.open(BlockGuardOs.java:254)
        at libcore.io.ForwardingOs.open(ForwardingOs.java:166)
        at android.app.ActivityThread$AndroidOs.open(ActivityThread.java:7542)

I’ve added android:requestLegacyExternalStorage="true" as stated in the documentation which nonetheless mentions only Android 10.

Expected Behavior

The expected behavior should be like on the previous Android version (10). I’ve tested the same code on the emulator and everything works fine.

Code Reproduction

I followed the official doc, so the snipped of code that causes the issue is very similar to one of the examples provided.

  async fileWrite(type: LogEventType, path: string, timestamp: string) {
    await Filesystem.writeFile({
      path: `${FILE_SYSTEM_CONFIGURATION.parentDir}/${path}.csv`,
      data: `${this.logEntryIndex}, ${timestamp}, ${type}\n`,
      directory: FilesystemDirectory.Documents,
      encoding: FilesystemEncoding.UTF8,
      recursive: true
    });

Other Technical Details

npm --version output: 7.4.3

node --version output: v14.8.0

Additional Context

I browsed and found related problems in other issues (link), but none of them targeting Android 11.

[xparadoxon]

For me it worked to set targetSdkVersion to 29 as in this version requestLegacyExternalStorage is supported, which then works on android 11 devices. Might not be the best way for future, but works. https://developer.android.com/about/versions/11/privacy/storage

[asztal]

Is this still planned for Capacitor 3?