Local folder picker crashes the app: UncheckedIOException from Files.list() escapes the IOException catch in FileHelper.listDirectoryEntries

[jrx-code]

⚠️ Before posting ⚠️

• This is a bug, not a question or an enhancement.
• I've searched for similar issues and didn't find a duplicate.
• I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
• I agree to follow Nextcloud's Code of Conduct.

Steps to reproduce

1. Settings → Auto upload → ⋮ → "Set custom folder".
2. In the local folder picker, browse into a large directory under /storage/emulated/0/Android/media/… (in my case com.whatsapp/WhatsApp/Media/WhatsApp Images, ~11 600 files, and its Sent subdirectory).
3. Keep the device busy at the same time (several auto-upload rules were uploading in the background here).

The directory read fails part-way through iteration with Software caused connection abort from the emulated-storage layer. That failure is intermittent and I cannot trigger it on demand — but when it happens, the app dies instead of showing an empty/partial list.

Expected behaviour

A failed directory read is logged and the picker shows what it could read (the catch in FileHelper.listDirectoryEntries is clearly written with exactly that intent).

Actual behaviour

The whole app is killed. The exception escapes the background executor task, so there is no chance to recover.

The catch cannot fire, and this is visible in the source rather than inferred:

FileHelper.listDirectoryEntries (34.1.1) uses Files.list(...), whose lazy stream reports directory-read failures from the terminal operation as java.io.UncheckedIOException — a RuntimeException, not an IOException:

return try {
    Files.list(directory.toPath())
        .map { it.toFile() }
        …
        .collect(Collectors.toList())
} catch (e: IOException) {          // never reached for UncheckedIOException
    Log_OC.d(TAG, "listDirectoryEntries: $e")
    emptyList()
}

LocalFileListAdapter.loadRemainingEntries() calls it on a pool thread with no guard, so the UncheckedIOException terminates the thread and takes the process with it.

Two small notes that may save reviewer time:

• Adding catch (e: UncheckedIOException) (or catching its cause) next to the existing IOException branch restores the intended behaviour.
• FileHelper on master has since been rewritten to forEachDirectoryPage using Files.newDirectoryStream with catch (IOException) + catch (DirectoryIteratorException), which does cover the iteration failure. So master may already be fine and this report is mainly about the released 34.1.1 line — worth confirming whether a backport is wanted.

Android version

17

Device brand and model

Samsung SM-F976B (Galaxy Z Fold8), stock

Stock or custom OS?

Stock

Nextcloud android app version

34.1.1 (340010190, gplay)

Nextcloud server version

31.0.14

Using a reverse proxy?

Yes

Android logs

Cause of error

Exception in thread "pool-27-thread-1" java.io.UncheckedIOException: java.nio.file.FileSystemException: /storage/emulated/0/Android/media/com.whatsapp/WhatsApp/Media/WhatsApp Images/Sent: Software caused connection abort
    at java.nio.file.Files$2.hasNext(Files.java:3729)
    at java.util.Spliterators$IteratorSpliterator.tryAdvance(Spliterators.java:1949)
    at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:156)
    at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:592)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:578)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:564)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:267)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:748)
    at com.nextcloud.utils.FileHelper.listDirectoryEntries(FileHelper.kt:31)
    at com.owncloud.android.ui.adapter.LocalFileListAdapter.loadRemainingEntries(LocalFileListAdapter.java:434)
    at com.owncloud.android.ui.adapter.LocalFileListAdapter.lambda$swapDirectory$2(LocalFileListAdapter.java:405)
    at com.owncloud.android.ui.adapter.LocalFileListAdapter.$r8$lambda$EFQ1jO9hT3yhM5CFqUk4qO5Vyvg(LocalFileListAdapter.java:0)
    at com.owncloud.android.ui.adapter.LocalFileListAdapter$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1100)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:1572)
Caused by: java.nio.file.FileSystemException: /storage/emulated/0/Android/media/com.whatsapp/WhatsApp/Media/WhatsApp Images/Sent: Software caused connection abort
    at sun.nio.fs.UnixDirectoryStream$UnixDirectoryIterator.readNextEntry(UnixDirectoryStream.java:180)
    at sun.nio.fs.UnixDirectoryStream$UnixDirectoryIterator.hasNext(UnixDirectoryStream.java:210)
    at java.nio.file.Files$2.hasNext(Files.java:3727)
    …

App information

• ID: com.nextcloud.client
• Version: 340010190
• Build flavor: gplay

Device information

• Brand: samsung
• Device: q8q
• Model: SM-F976B
• Id: CP2A.260605.016
• Product: q8qxeea

Firmware

• SDK: 37
• Release: 17
• Incremental: F976BXXS2AZH7