[Nix-dev] Package maintainer coordination problem and Nix

[Marc Weber]

Hi Mad,

I'm glad you finally had the time to look into nix(os)!

You're welcome!

The nix language is able to express what you're looking for.
Nobody has done so by now.
Evaluation time will increase though.

Andres (kosmikus on irc) made a student (J-roen) work on haskell packages.
And I think he has something like this in mind as well.
For haskell packgaes it actually makes sense because configuring with
flags is scomplex but still doable in nix language.

What you tell is true. And it actually happened the last time
stdenv-updates was merged in. sudo update broke a script launching qemu.
It took me one week to track it down. But I had the choice and could
choose when to upgrade!

Maybe think about it differently: One of the main strength of nix(os) is
that if an upgrade fails you can switch back easily. So you may upgrade
safely knowing that you don't have to work at night cause if it fails
you can switch back. This kind of safety is one reason for me using
nix(os). Another issue I was faced with was the update of gcc. gcc and
those -O2 optimization settings made php behave strange catching
exceptions. Using -O0 fixed it.

So we are at the point: How does this description of dependencies look
like?

 gcc = version X  then use -O2
 gcc = version Y then don't use -O2,-O1,-O3 ..

....
And you already see that it's a very much work to figure this out and
test it. I don't even think we have the resources to do so.

But: If a package breaks for one of teh reasons you mentioned nix(os) is
the only distribution I know letting you do a git bisect to find the
"change" causing the failure easily. Of course this takes time. But
using debian or gentoo I don't even know where to start because
everything you have is emerge sync (which rsyncs all the package
descriptions).. Of course you can put this into git yourself but you
can't rollback easily if you broke the system.

Let's have a short look at systems which do what mentioned:
python: setup-tools (easy-install), eggs:
  quote: It's considered a bug if you require administrative priviledges
php: pear
ruby: rubyforge, ruby-gems
Eclipse and its plugin system (which provides its own rollback facility)
haskell + hackage..

And indeed they cause some headache to me because I'm not sure whether
I should package those stuff or just use it using easy-install and pear
update etc..

I worked on ruby recently. I solved it by adding a gem nix command which
creates a set of nix expression from those dynamic dependencies.
The result is that you can just do nix-env -iA sup and it works.
You can't do so on debian, can you?

So you could say nix is good at taking snapshots of software configurations
which play together nicely.

Dependency and upgrade hell can't be solved in general but:
using nix I know that when doing nix-collect-garbage everything is gone
I no longer need.

Eg the plone buildout system doesn't remove old cruft AFAIK.

And yes: You have found one bad point about nix: If you upgrade X an old
tool does no longer work. Actually this is an issue if you use special
kernels. Eg ghc can't be compiled easily because binaries don't work as
expected etc.

Nix even adds a new source of problem: You can't force users to upgrade
their packages (thus fixing security issues).

Anyway: the benefits are more important to me.. Even if you don't
upgrade for two years you can still do so by using nix-install-package
which installs the new required tools from urls. I don't think you can
do this using debian or gentoo.

Let me show you another nice point about nix: It's easy to install
source (and generate tags automatically) along with libraries.
Do you know any other system allowing you doing so ? [1]

Anyway you've heard that nix can let you experiment with these ideas while
keeping the system running. That's most important to me.

Marc Weber

[1]

for haskell it looks like this (this install most packages which are availible at the moment)
The last map adds the source derivation which also contains the tag files.

put this into your config.nix:

    haskellCollection = 
     let hp = haskellPackages;
         install = 
        [ 
          hp.alex hp.cabalInstall /*hp.ehc*/ hp.frown /* hp.haddock09
          hp.haddock210 hp.haddock */ /*hp.happy117 hp.happy*/ hp.Agda /* hp.benchpress */ hp.binary
          hp.cgi hp.convertible hp.cpphs hp.Crypto hp.dataenc hp.digest hp.dotgen
          hp.editline hp.emgm hp.extensibleExceptions hp.fgl hp.ghcPaths hp.GLUT
          hp.gtk2hs hp.haskeline hp.haskellPlatform hp.haskellSrcExts hp.haskellSrc
          hp.haskellSrcMeta hp.HaXml /*hp.haxr hp.haxr_th */ hp.HDBC /* hp.HDBCPostgresql */
          hp.HDBCSqlite hp.Hipmunk hp.hscolour hp.html hp.HTTP hp.HUnit hp.ivor hp.json
          hp.leksah /*hp.maybench*/ hp.monadlab hp.MonadRandom hp.mtl hp.multirec hp.network
          /*hp.nonNegative*/ hp.numericPrelude hp.OpenAL hp.OpenGL hp.pandoc hp.parallel
          hp.parsec hp.pcreLight hp.QuickCheck hp.QuickCheck2 hp.readline hp.regexBase
          hp.regexCompat hp.regexPosix hp.SDL hp.SDLImage hp.SDLMixer hp.SDLTtf
          hp.Shellac hp.ShellacHaskeline hp.ShellacReadline hp.stm hp.storableComplex
          hp.strictConcurrency hp.terminfo hp.testpack hp.time hp.time113 hp.uniplate
          hp.utf8String hp.utilityHt hp.uuParsingLib hp.uulib hp.vacuumCairo hp.vacuum
          hp.vty /*hp.wx hp.wxcore*/ hp.X11 hp.xhtml hp.zipArchive hp.zipper hp.zlib
          /* hp.helium */ /*hp.hlint*/ hp.idris hp.lhs2tex hp.MazesOfMonad hp.uuagc hp.xmobar
          hp.xmonad hp.xmonadContrib

          hp.hslogger hp.tar hp.bytestring hp.networkBytestring hp.syb
          hp.ghcSyb hp.getOptions hp.multiset hp.filepath
          hp.hsloggerTemplate
        ];
      in
      misc.collection {
        name = "haskell";
        list = [ hp.ghc ] ++ install ++ (map (x : sourceWithTagsDerivation (sourceWithTagsFromDerivation (addHasktagsTaggingInfo x) ))
                            (lib.filter (x : builtins.hasAttr "src" x) install
                            ++ [ (hp.ghcReal // { srcDir = "libraries"; }) ] ) );
      };