Can confirm with Dolphin 19.11.70 on KDE Neon Git Unstable.

Could you please create a tar.gz archive with a file named this way and add it here?

Created attachment 121937 [details]
Example file with invalid encoding

The file can be deleted via its inode:
> find . -inum ${inode} -delete

Created attachment 121938 [details]
Minimal example project

It seems that the faulty encoding vanishes when I download the attachment with the FireFox.
That's why I created a minimal C++ example project. However it requires the ROOT framework to be installed.

The "Form" function used is the following:
https://root.cern.ch/doc/master/classTString.html#aeb44d6183d8b1f1b7090dbd3c93f5e39

I am sorry that I cannot deliver any other samples right now.

I found a workaround: 

In Dolphin do:

* Create a new folder
* Move the weird files to this new folder with Dolphin
* Delete the folder, ie the folder moves to trash
* Delete the folder in the trash

Just deleting the files directly does not work.

> It seems that the faulty encoding vanishes when I download the attachment with the FireFox.

That's the reason I requested a tar.gz file which contains a file using a not working name.

I should have mentioned that I tried to this but failed:
> tar -czf test.tar "\'\'$\'\020\365\226\377\177\'\'_Encoding.root\'"
as tar will rename the file making the sample useless.

However you can do this:

> touch testfile
> mv testfile ''$'\020\365\226\377\177''.test'

:-)

> mv testfile ''$'\020\365\226\377\177''.test'

I could delete the file using Dolphin. Need more information how to reproduce.

The minimal sample I found, which I cannot delete, is
> touch $'\300'
or any number greater than 300. Below it will create an ASCII, for example
> touch $'\100'
will create a file named "@"

I am not sure why you are able to delete it. Maby you use a filesystem other than ext4?
Which additional information could I give you?

I am also using ext4. Are you using a UTF-8 locale?

set | grep ^L[AC]

> set | grep ^L[AC]

> LANG=de_DE.UTF-8
> LANGUAGE=
> LC_ALL=de_DE.UTF-8
> LC_NAME=de_DE.UTF-8

If you say that you are able to delete a directory that contains such a file, the bug isn't in kio. Needs someone to further investigate.

Created attachment 123697 [details]
Video which demonstrates the issue.

I tried it again and I can no longer delete the folder with the weird file within Dolphin but with the "rm" command in a terminal. So it is likely related to KIO.

I made a video for you: 

* Create a weird file
* Rename it
* Undo renaming
* Try to delete it
* Move it to a folder
* Delete the folder, ie move it to the trash
* Try to empty the trash
* Try to remove the folder in the trash
* Remove the folder with rm -rf
* Press F5 to update the cache so Dolphin notices that the Folder and file are actually gone


System update:

Operating System: Manjaro Linux 
KDE Plasma Version: 5.17.2
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.1

For the video I used a freshly created user account.

However, a friend of mine, who is on Manjaro KDE as well, could not reproduce it unfortunately. Maybe I should try to reinstall my system or test it with a live version?

I haven't investigated properly, but if you are trying to delete files inside trash:// KIO slave instead of using the file:// slave, then it probably cannot work because the encoding hack to support broken file names was only added for the file:// slave.

(In reply to Christoph Feck from comment #16)
> if you are trying to delete files
> inside trash:// KIO slave instead of using the file:// slave, then it
> probably cannot work because the encoding hack to support broken file names
> was only added for the file:// slave.

That's why the file in the folder is not displayed in Dolphin for trash:// but only for file:// 

Displays the file:
> /home/user/.local/share/Trash/files/foo/

Does not display the file:
> trash:/0-foo/

Moving to confirmed as it seems Christoph and Postix have confirmed where the issue lies.