Cancelling an upload does not really cancel it

[nicolas-raoul]

Scenario: You upload 5 pictures of a monument, but while it is uploading you suddenly realize that two of the pictures are privacy violations (for instance they are private family pictures). You want to cancel these two uploads, so for each of them you tap the pause button then the "X" delete button.

Problem: These two pictures actually get uploaded as well.

This is probably a rather difficult issue, as you will need to read the code and understand how the app retries failed uploads.

[RitikaPahwa4444]

For me, the cancel button is working correctly only for the ongoing upload. For the upcoming contributions, this does not work, which means only the first contribution in the queuedContributions list is impacted by the delete operation. Tapping the button apparently deletes the contribution from the database, so the retry logic should not find the entry at all🤔

apps-android-commons/app/src/main/java/fr/free/nrw/commons/contributions/ContributionViewHolder.java

Lines 240 to 243 in 64652b9

	@OnClick(R.id.cancelButton)
	public void deleteUpload() {
	callback.deleteUpload(contribution);
	}

[RitikaPahwa4444]

I suspect if this line adds the contribution again to the database using the insert operation:

apps-android-commons/app/src/main/java/fr/free/nrw/commons/upload/worker/UploadWorker.kt

Line 219 in 64652b9

contributionDao.saveSynchronous(contribution)

[nicolas-raoul]

Thanks Ritika, great insight! :-)

[RitikaPahwa4444]

May I take this up? Since this issue is very similar to my GSoC task (#5136), I was curious to explore and find some more solutions.

The cause is exactly the same: queuedContributions list does not get updated once it has fetched the contributions from the database. So, one way to fix this issue is to replicate that idea. I've got a few more ways to approach this issue:

• We're using a one-shot query, so using an observable query might also help. This seems like an intuitive way to me, but needs to be handled carefully.
• The approaches above will require us to check the database frequently for any changes. These database calls could be avoided altogether using an in-memory hashset for cancelled uploads, just like the one we've for paused uploads.

[nicolas-raoul]

@RitikaPahwa4444 Please do not feel obligated to, but if you want to take it then of course you are more than welcome! :-)