[SOLVED] How to properly install optionnal dependencies ?

Question

Hi,
As stated in the title, I don't know how to install optionnal dependencies : (let's take an example)
I noticed that with libva comes two optional dependencies libva-intel-driver and libva-vdpau-driver, and as I have an intel graphic card, I would like to install libva-intel-driver.
But to keep my package tree quite clean, I would like to install it as a dependency of libva, this way, if someday I want to remove libva, libva-intel-driver will be removed too.
In the pacman manual, the option --asdeps seems to be useful to install a package as a dependency (but it doesn't seems to need to specify which package it is a dependency for).
So my question is, does this mean that libva-intel-driver will be removed when I don't need libva anymore ?
And more generally, how pacman manage dependency ?
As a matter of fact, I tried to install and then remove libva-intel-driver, but it never said that libva might need it.
tl;dr : I want to install an optionnal dependencies exactly like a regular dependencies would be installed : how could I do that ?
Edit:
the answer is here : https://wiki.archlinux.org/index.php/Us … OptDepends
Last edited by gravitezero (2012-10-10 12:04:25)

Answer 1

If you install it with --asdeps, which package it is a dependency for is listed in the packages info file that goes into pacman's database.
Imagine you have packages A B and C, C is a dependency of both A and B, but for whatever reason you install C first with "--asdeps", then you install A and B.  If you later remove A with "pacman -R A" no dependencies will be removed, but if you use "pacman -Rsn A" A will be removed as will all of it's dependencies that are not needed by any other package.  So in this case C would still not be removed as B still needs it.  If you then "pacman -Rsn B" B and all it's dependencies including C would be removed.
That is how it works for normal dependencies.  I don't believe optional dependencies have database entries in the "required by" field as they are not required, they are optional.  So if C were only an optional dependency of A and B, it would never be removed by removing A and/or B (AFAIK).
If you install libva-intel-driver with "--asdeps" then it will likely show up in "pacman -Qdt" output.  If you later install anything that has libva-intel-driver as a regular dependency, then later remove that package with "pacman -Rsn" libva-intel-driver will be taken away with it - it is doubtful you would want this.  So don't install optional dependencies "--asdeps"
They are optional, you are opting for them, install them normally.
Alternately, and as a direct answer to your real question, I believe the only way to do with would be to modify the package info of libva to switch libva-intel-driver from optional to regular dependency.  This would be easy to do, but I don't know if it's easy to automate, nor would it survive udates to libva, it'd have to be redone.
Last edited by Trilby (2012-10-10 11:21:06)