Allow uploading files while preserving the actual lastModified date

[adil192]

My app Saber uses the last modified date of files to sync. Currently when a file is uploaded, its last modified date on the server is set to the upload time.

Proposition

// before
await webdav.upload(bytes, filePath);
// after (optional {DateTime? lastModified} parameter)
await webdav.upload(bytes, filePath, lastModified: someDateTime);

Alternatives I've considered

I've tried setting the lastModified props like this, but it didn't show any change in the Nextcloud web interface.

// upload file
await webdav.upload(bytes, filePath);

// set lastModified to match local file
await webdav.updateProps(filePath, {
  WebDavProps.davLastModified.name: someDateTime.toString(),
  WebDavProps.ncUploadTime.name: someDateTime.toString(),
});

---

nextcloud/server#15192

I can add that uploading files into nextcloud by using WebDAV also doesn't preserve the original timestamps.

not technically possible because the Webdav protocol doesn't include the local modification time

Nextcloud has a custom header X-OC-Mtime that the desktop client and the web UI sets to preserve it.
Third party clients would need to be modified to also pass this...

I'm not well-versed on Nextcloud but perhaps we need to use something other than webdav?

---

The Nextcloud desktop client sets the header like this:

QMap<QByteArray, QByteArray> PropagateUploadFileCommon::headers()
{
    QMap<QByteArray, QByteArray> headers;
    headers["OC-Async"] = "1";
    headers["Content-Type"] = "application/octet-stream";
    headers["X-OC-Mtime"] = QByteArray::number(qint64(_item->_modtime));

[provokateurin]

I'm on vacation right now, but I'll look into it when I'm back. Updating the date via props should definitely work, maybe you need to use a different format?

[adil192]

I tried both someDateTime.toString() and someDateTime.toIso8601String(). I wasn't sure what format Nextcloud accepted but didn't know where to look to find out

[adil192]

Just tried this DateFormat but no luck
https://github.com/provokateurin/nextcloud-neon/blob/e916fcd8f8bfe840f96f68145a2e32c994404a40/packages/nextcloud/lib/src/webdav/file.dart#L79

DateFormat('E, d MMM yyyy HH:mm:ss', 'en_US').format(lastModified);

[provokateurin]

Hey sorry, I didn't have the time yet. I hope I can look at it this or next week.

[adil192]

Hey sorry, I didn't have the time yet. I hope I can look at it this or next week.

There's no rush, this is a really low priority feature request from my end :)

[provokateurin]

I found out that modifying the last modified time via the prop is not possible since it is readonly. The only way is to set it at upload time like I did it in the PR.