Syncs (downloads) continue over mobile data per default without a warning or ability to configure

Actual behaviour

The app synchronizes over mobile data per default WITHOUT a warning or asking about it even once - that's bad since traffic-limited plans (with either significantly degraded functionality or highly increased cost after exceeding the overall traffic volume) are still the norm for many European countries, and I assume also most of the US.

Expected behaviour

Sync over wifi only, or make a big(!) popup at the start that warns me about this default setting of syncing over data and offer an obvious button to turn that off.

Steps to reproduce

1. Install & open nextcloud app
2. Login to a cloud
3. Choose an existing folder on the server with existing content on the server (a non-trivial amount of files), which isn't present / synchronized to the phone storage yet. Click the "Sync" button from the folder menu on the right. The app should now start downloading things to the phone storage
4. Get out of wifi range with mobile data enabled, and observe that synchronization / downloading will continue

Environment data

Android version: 7.1.2

Device model: GT-I9195 / serranoltexx / Samsung Galaxy S4 Mini LTE (International version)

Stock or customized system: LineageOS 14.1

Nextcloud app version: 3.0.3 / f-droid

Nextcloud server version: don't know

Logs

Web server error log

issue seems to be server independent, currently not having any access to the server I tested with

Nextcloud log (data/nextcloud.log)

issue seems to be server independent, currently not having any access to the server I tested with

[mario]

a) I assume you mean auto upload?
b) default is actually unmetered wifi only
c) Issue happens when an upload starts on wifi, but finishes on mobile? Because that's expected.

No I mean download during initial synchronization. (Folder wasn't present on phone before) But I guess upload might be affected as well? I didn't test that though, so I don't know.

c) Issue happens when an upload starts on wifi, but finishes on mobile? Because that's expected.

It started downloading new files after the connection switch - and if that's intentional, I think that's a bad default behavior. Synchronization should stop without wifi and resume later when it's back, OR I should be warned that it continues during no wifi / mobile data connectivity with an option to disable that behavior.

[tobiasKaminsky]

The current assumption is that if an user clicks on a file/downloads a directory he wants to have the content immediately and knows that this will cause traffic.

If we would have something like a download queue we could at a question if the download start now or be postponed, if file/folder is > 10Mb (e.g).

I am unsure if we really talk about downloading/syncing. When you enter an unknown folder, only the metadata (file name, folder name, size, date...) are downloaded, this is very very tiny. Only if you click on a file, this file gets downloaded.

The current assumption is that if an user clicks on a file/downloads a directory he wants to have the content immediately and knows that this will cause traffic.

I clicked the sync button while on wifi of an existing folder on the server, which has a couple of gigabytes worth of content. This made the app start to download all the files in the folder, or at least it looked like that to me. The synchronization / download continued when I lost wifi access and the phone switched to mobile data, which is why I filed this ticket. (I would have expected it to stop)

I am unsure if we really talk about downloading/syncing.

I pressed a folder and clicked "Sync" - so we're talking about whatever that does. I assumed it downloads files, but if you say that only downloads metadata then it's not as bad as I assumed. However, in the android file browser it looks like the files are actually retrieved locally, and the notifications of the nextcloud app said it was downloading files.

I edited my last comment to clarify a few things, hopefully that should clear a few things up. It certainly looked like the app was downloading full files to me, but I don't actually know.

[Cybso]

+1 for this issue. This behavior is quite unexpected. The download should either be paused when the user started sync while in wifi but leaves the network, or there should be a global setting whether any syncs should be done while on mobile networks (like in Play Music, for example).

It could also simply ask the user with a notification what to do. Anything would be better than the current oblivious behavior really