[Nix-dev] How to actually get rid of things from the nix-env -qs list?

[Mateusz Kowalczyk]

Hi,

I just finished packaging livestreamer and while doing it, I wanted to
try it out with multiple Python versions to see which work. I wrote the
relevant bit then set off to nix-env.

I run nix-env -f . -i python3.3-livestreamer, it installs and runs fine.
Great. Now I want to try the 2.7 version.

I run nix-env -f . -i python2.7-livestreamer and I'm told that there's a
collision. OK, I try ‘nix-env -e python3.3-livestreamer’ and then try
again. It still tells me there's a collision!

nix-env -qs shows something like

IP- python3.3-livestreamer-1.8.0

Where is the ‘IP-’ bit documented? As far as I know, the last letter
indicates whether the software is currently active. I don't understand
why it complains about collisions after I uninstalled (with ‘-e’) the
3.3 version: there should be no problem, right?

After messing with priorities for a while, my -qs looks like

IP- python2.7-livestreamer-1.8.0
IP- python3.3-livestreamer-1.8.0

Well, I managed to install the software with both 2.7 and 3.3 but I have
no idea which one is active at the moment. I also don't know how to get
rid of 2.7 from my -qs list which I don't care about: I only wanted to
test that it worked when writing the package. How can I do this? Is
nix-env -i a bad way to test these things?

Thanks
-- 
Mateusz K.