Crash when loading "Deleted files"

[Kiaatix]

Nextcloud app version:
3.3.1
Nextcloud server version:
14.0.3

The app crashes when there are many files with equal names in the trashbin.

Stack trace:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.nextcloud.client, PID: 10317
    java.lang.IllegalArgumentException: Comparison method violates its general contract!
        at java.util.TimSort.mergeHi(TimSort.java:895)
        at java.util.TimSort.mergeAt(TimSort.java:512)
        at java.util.TimSort.mergeCollapse(TimSort.java:437)
        at java.util.TimSort.sort(TimSort.java:241)
        at java.util.Arrays.sort(Arrays.java:1523)
        at java.util.Collections.sort(Collections.java:238)
        at com.owncloud.android.utils.FileSortOrderByName.sortTrashbinFiles(FileSortOrderByName.java:76)
        at com.owncloud.android.ui.adapter.TrashbinListAdapter.setTrashbinFiles(TrashbinListAdapter.java:89)
        at com.owncloud.android.ui.trashbin.TrashbinActivity.showTrashbinFolder(TrashbinActivity.java:256)
        at com.owncloud.android.ui.trashbin.TrashbinPresenter$1.onSuccess(TrashbinPresenter.java:72)
        at com.owncloud.android.ui.trashbin.RemoteTrashbinRepository$ReadRemoteTrashbinFolderTask.onPostExecute(RemoteTrashbinRepository.java:211)
        at com.owncloud.android.ui.trashbin.RemoteTrashbinRepository$ReadRemoteTrashbinFolderTask.onPostExecute(RemoteTrashbinRepository.java:175)
        at android.os.AsyncTask.finish(AsyncTask.java:660)
        at android.os.AsyncTask.-wrap1(AsyncTask.java)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:677)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6077)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

I think it's because AlphanumComparator().compare(o1, o2); always returns -1 for identical filenames (at least for files with a '.' in their name) in com.owncloud.android.utils.FileSortOrderByName:84.

Workaround:
if (o1.getFileName().equals(o2.getFileName())) return 0; before FileSortOrderByName.java:84

[nextcloud-android-bot]

GitMate.io thinks possibly related issues are #2574 (crash on file delete), #2515 (Crash at files loading), #2281 ([Deleted]), #117 (Crash when last account is deleted), and #1695 (Crash when trying to upload many files).

[tobiasKaminsky]

Can you give some sample names where this occurs?
We have multiple test cases for sorting, and I assumed that handling "." in it is working.

Do yo really have two files with the exact same file name? Otherwise your workaround would not apply?

[AndyScherzinger]

We also have a fix which has been contributed a couple of days ago regarding sorting which might already fix this.
Could you test the dev version available on f-droid?

[tobiasKaminsky]

I tested this with latest master:

• created 1.txt & deleted it
• created 1.txt & deleted it
• open up deleted files
• see two times 1.txt, but no crash

[Kiaatix]

OK the dev-version works for me, so the issue can be closed.

To reproduce the error is quite difficult. It just happened in my private account with thousands of files in the trash-bin. The filename where it eventually crashed was 2b(Kd=0).png
There were 4-5 files with that name.

I was able to track down that it was because third_parties.daveKoeller.AlphanumComparator#compare(java.lang.String, java.lang.String) always returns -1 if both inputs have this value, eventually stating that
element1 < element2 and element2 < element1, which is not possible in a total order.

Technically, most sorting-algorithms should still terminate correctly; it should just result in unnecessary swaps.
I'm not really familiar with Java and how it detects "Comparison method violates its general contract!" when sorting. Maybe the detection depends on the position of the files in the list, or it's size (more recursions/iterations of the sorting algorithm)...