Trimming XDG_DATA_DIRS to not contain duplicates

[dr460nf1r3]

Hello everyone

I have the following question: how can I trim the generated XDG_DATA_DIRS environment my DE uses to the non-duplicated paths only?

I noticed KDE apps are insanely slow to start compared to other distributions. Read about XDG_DATA_DIRS duplicates causing the startup here:

Plasma Emojier Too Slow, Episode IV

Episode V: The real culprit! tl;dr: Maybe things will be solved with plasma 6.0, they were solved on the kde2nix repo. Long read: Like I commented also on the Quadratic thread, I also have struggled with this. On plasma5, some apps take much more than on arch, for example. Dolphin for example, is one, while konsole is not so much affected. After lots and lots of benchmarks and searching and testing stuff (like preload, but didnt solved it), etc, I stumbled in a bug report (which google now f…

And in fact, there are tons of duplicates, mostly KDE-related.

 nico@dragons in ~ 
❯ echo $XDG_DATA_DIRS | tr ':' '\n' | wc -l
203

 nico@dragons in ~ took 6ms
❯ echo $XDG_DATA_DIRS | tr ':' '\n' | sort | uniq | wc -l
87

The full list of entries can be found here.
I have a script to export this variable without the unnecessary duplicates, which I would like to run during login. I tried programs.bash.loginShellInit, as well as home-managers option for appending content to .bashrc, but both of these fail to reduce the amount of paths set in XDG_DATA_DIRS.

So I’m assuming something else exports the variables, overwriting my changes. Any idea how to proceed here?

My flake can be found here, using latest nixpkgs-unstable with KDE 6.