Delete uploaded files when answer is deleted

[do-it4fun]

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Describe the bug
I have a form in which participants can attach files to their answers. If I delete an answer, the corresponding files are not deleted, which leads to unnecessary storage consumption.

To Reproduce
Steps to reproduce the behavior:

1. Create a form with a question of the type file
2. Answer the form and upload a file
3. A new folder is created for the uploaded file:

4. In the Form go to Results > Answers and delete the answer using the 3-dot menu:

6. The answer is deleted from the overview.
7. The previously created subfolder for the answer containing the uploaded file remains.
8. Expected behavior: The subfolder of the corresponding answer and the containing files should be deleted when the answer is deleted.

Nextcloud (please complete the following information):

• Nextcloud-Version: Nextcloud Hub 9 (30.0.6)
• Forms-Version: 5.0.4

Additional context
The form is shared with other users who can also delete the answers, but it does not matter which user deletes the answer.

[Koc]

@Chartman123 yeah, we can improve that. But before we've started, let's clarify few things:

• do we need ask for file removal confirmation? I mean is it possible to remove submission but keep files?
• am I right that we should do the same for question/form removal?
  • do we need introduce async job for cleanup or do everything in same request?
• do we need cleanup just files or empty folders as well?

[Chartman123]

• do we need ask for file removal confirmation? I mean is it possible to remove submission but keep files?

Would be nice... I think it depends. When I use this question type I normally take the files from the upload folder and put them somewhere else. In this case the folders/files can also be deleted when I delete the submission.

• am I right that we should do the same for question/form removal?

Yes, definitely makes sense. The rest of data will then also be deleted from the database if I remember correctly, at least when the whole form gets deleted.

• do we need introduce async job for cleanup or do everything in same request?

I'd say that we should delete the files directly upon deletion of the submission/question/form + scheduled job that cleans up remaining files?

• do we need cleanup just files or empty folders as well?

Empty folders would be great, too, but they are already deleted by the existing cleanup job, aren't they?

@susnux what do you think?

[Chartman123]

As I'm currently finishing the PR to allow editing of a user's submissions and this involves also that the user is then able to delete his submission, we need to take these actions into account, too.

When a user edits his submission for a form with a file question, the old file should get removed and the new file should be stored.

When a user deletes his submission, corresponding files should also be deleted.

Both cases of course can fail, if the form owner already moved the files out of the submission folder.