Reset last sync date of files written via DocumentsProvider

[grote]

The sync operation detects changes by comparing timestamps in milliseconds. However, the local modification time only has a precision of seconds (even though given in milliseconds).
When the DocumentsProvider is used programmatically, operations such as a create and a subsequent write can happen within the same second causing the sync operation to not detect the change and therefore failing to upload a file causing data loss.

This MR also moves the file close listener to the thread used by the DocumentsStorageProvider as this is more appropriate than the UI thread.

Fixes #6726 (I can create other tickets about the side-issues identified there)

[tobiasKaminsky]

The sync operation detects changes by comparing timestamps in milliseconds. However, the local modification time only has a precision of seconds (even though given in milliseconds).

While reviewing this I tried to find where we use precision of seconds, as we then should change this, but I cannot find it?
OCfile:getLocalModificationTimestamp() uses File.lastModified which is in millis.

[grote]

While reviewing this I tried to find where we use precision of seconds, as we then should change this, but I cannot find it?
OCfile:getLocalModificationTimestamp() uses File.lastModified which is in millis.

Sorry for not explaining this better. The precision used is actually not obvious and I only found out about it with a long debugging session pinning down the bug that was probably introduced because millsecond precision is assumed as the java docs talk about the time being in milliseconds. Eventually I noticed that the last three digits of the getLocalModificationTimestamp() were always 0. I did many test runs and they always stayed at zero.

Here's a related SO question: https://stackoverflow.com/questions/24804618/get-file-mtime-with-millisecond-resolution-from-java
Somebody claims that this is fixed in Java 9, but on Android 10 (which should use Java 9 internally) I also get second precision only.

Note that this PR is superfluous once #6753 is implemented. However, since we don't know when this will land, it might make sense to merge this one already since it fixes a rather serious data-loss bug.

[tobiasKaminsky]

Thanks for your detailed explanation!
So we cannot do anything on our side, as we are already ready for millis :-)

Then let us get this in 👍

[nextcloud-android-bot]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/15527.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[nextcloud-android-bot]

Codacy

405

Lint

Type	master	PR
Warnings	81	81
Errors	0	0

SpotBugs (new)

Warning Type	Number
Bad practice Warnings	27
Correctness Warnings	61
Internationalization Warnings	9
Multithreaded correctness Warnings	9
Performance Warnings	73
Security Warnings	44
Dodgy code Warnings	106
Total	329

SpotBugs (master)

Warning Type	Number
Bad practice Warnings	27
Correctness Warnings	61
Internationalization Warnings	9
Multithreaded correctness Warnings	9
Performance Warnings	73
Security Warnings	44
Dodgy code Warnings	106
Total	329

[codecov]

Codecov Report

Merging #6751 into master will increase coverage by 0.07%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #6751      +/-   ##
============================================
+ Coverage     27.81%   27.88%   +0.07%     
  Complexity        5        5              
============================================
  Files           427      427              
  Lines         34237    34239       +2     
  Branches       4735     4735              
============================================
+ Hits           9522     9549      +27     
+ Misses        23297    23260      -37     
- Partials       1418     1430      +12     

Impacted Files	Coverage Δ	Complexity Δ
...ud/android/providers/DocumentsStorageProvider.java	3.08% <0.00%> (-0.02%)	0.00 <0.00> (ø)
.../third_parties/daveKoeller/AlphanumComparator.java	82.14% <0.00%> (-1.20%)	0.00% <0.00%> (ø%)
...oud/android/operations/RefreshFolderOperation.java	70.99% <0.00%> (-1.15%)	0.00% <0.00%> (ø%)
...oud/android/ui/activity/SyncedFoldersActivity.java	24.16% <0.00%> (ø)	0.00% <0.00%> (ø%)
...loud/android/datamodel/FileDataStorageManager.java	52.58% <0.00%> (+0.31%)	0.00% <0.00%> (ø%)
...loud/android/datamodel/ThumbnailsCacheManager.java	38.90% <0.00%> (+0.36%)	0.00% <0.00%> (ø%)
...d/android/operations/SynchronizeFileOperation.java	1.05% <0.00%> (+1.05%)	0.00% <0.00%> (ø%)
...va/com/owncloud/android/utils/FilesSyncHelper.java	17.33% <0.00%> (+1.33%)	0.00% <0.00%> (ø%)
.../owncloud/android/files/services/FileUploader.java	50.41% <0.00%> (+1.44%)	0.00% <0.00%> (ø%)
.../java/com/nextcloud/client/jobs/OfflineSyncWork.kt	35.59% <0.00%> (+27.11%)	0.00% <0.00%> (ø%)