Hi Malcolm, Malcolm Matalka <mmata...@gmail.com> writes: > Thanks for the complete response Marc. > > For the mean time, the current solution I'm working on is manually > converting packages to Nix. The translation is pretty straight forward > and I should be able to write a tool to automatically do it. It's not > optimal but I have been able to get all of the packages I care about > into my local nixpkgs repo and will submit them to the master repo once > I'm satisfied with them.
I like the approach of (semi-)automatically creating nix expressions. In my understanding (and I am pretty determined but happy to change it based on good arguments): A set of nix expressions always produces the very same output. For me this means (so far) that ad-hoc resolving dependencies within nix is not needed. I want to resolve dependencies ad-hoc when creating a new set of nix expressions, but not when I install a package via nix. Therefore the resolver belongs outside of nix. If I want to install things ad-hoc in a nix system, I need to create a bridge between a nix world where everything is determined and a fluent world where things are installed as they are available. These fluent things cannot reside in the nix store. Whether such dynamically managed things belong into /var or a user's home is another discussion. For nodejs I was quit happy that I got such a dynamic profile via: % npm config set prefix ~/.nodejs Now installing things "globally" end up in ~/.nodejs and the bins in ~/.nodejs/.bin, which I included in my path. Perfect quick and dirty installation of the view nodejs packages I need. For python we are aiming at something similar: generate nix expression and check them into git for commonly needed packages, use the rest via easy_install, but give the people the tool to create nix expressions for whatever they need. Looking forward to your ocaml work! regards forian > Marc Weber <marco-owe...@gmx.de> writes: > >> I created >> hack-nix for Haskell, which dumps hackage. contains a brute force >> dependency solver >> >> nixpkgs-ruby-overlay [1] which dumps rubyforge (which is quite usable, but >> not perfect yet) >> nixpkgs-python-overlay [2] which dumps PyPi (experimental, dependency >> inforamtion is not complete enough) >> does not do backtracking, if dependencies fails its you having to to >> tell it "try lib-A version 2.0.0". >> >> They are special because they all work on a "dump of packages" creating >> .nix derivations on the fly whereas cabal2nix creates .nix files very >> close to what you find in nixpkgs. >> >> They all create kind of shell script you can source to augment the >> environment variables, so that dependencies are found. >> Thus you can have multiple "sets of packages" for different targen >> porjects within the same user account without conflicts - however you >> always have to load such an environment, eg by >> >> # run bash with ruby packgaes found in environment "name" >> ruby-env-name bash >> >> Known additional universes: >> - perl >> - java, scala (ivy, maven, sbt) >> - .... >> >> There are many ideas and ways to implement such. >> Eg for scala/maven/ivy/... one way to think about it would be using the >> store as "installation place", but not using much about the nix* tools >> otherwise. >> >> then sbt build would just store everything in store. >> Other ways are creating .nix files for a target on the fly - such as >> sbt/ivy/mvn create-nix-derivations (which is close to what cabal2nix >> does). >> >> The downside is that you may have to run a tool before you can succeed >> with nixos-rebuild-switch, because not everything may be packaged. >> >> The perfect way would be including a SOT solver in nix, which hasn't >> beeen done yet - and which was not favored by Eelco in the past (maybe >> for good reason). Eg Eclipse plugin system works this way: the SAT >> solver tries to find one working set of dependencies to satisfy the >> setup you want - however the search space may be very big - which is why >> I limit the simple brute force solver used by hack-nix by passing only a >> subset of all packages found on hackage (latest versions & same manually >> selected ones). >> >> While such a generic approach may seem perfect, there are these >> downsides: >> >> - its harder to controls when rebuilds will take place, because small >> changes in the pool may cause the solver arbitrarely choose a >> different solution, otherwise its you having to force eg library-A >> version should be 1.0 like thing. >> >> and such rebuilds are bad, because its easy to loos track about which >> combinations actually work, because while constrtaints are fine, they >> are never complete. >> >> Thus in any case there will be lots of maintainance effort. >> >> - its also hard and time consuming (for humans and the cpu) to evaluate >> all solutions over and over again - which may not be the perfect end >> user experience. Eg you do'nt want wont to wait 30secs for the >> evaluation to finish just to install "gnu sed" >> >>> translation apps for all language package manager types? Specifically I >>> am looking at opam, the new ocaml package manager. >> I never used opam. >> >> Can you copy paste a package description with dependency information so >> that we can get an idea about how it actually looks like? >> >> Cabal is kind of "static", but very complex. >> Example: >> http://hackage.haskell.org/packages/archive/darcs/2.8.3/darcs.cabal >> scroll down to "build-depends" which depend on "flags" which are >> automatiacally chosen depending on the ghc version available - but >> flags are also used to enable/disable features or test cases >> >> for python and ruby there are .py or gemspec files. >> The problem is that they may even run python or ruby code - thus >> there may be packages whos dependencies may depend on configuration >> options and or the system which makes it harder to to dump such info >> into something which can be read and used by nix. >> >> [1] ruby: http://gitorious.org/nixpkgs-ruby-overlay >> [2] python: http://gitorious.org/nixpkgs-python-overlay >> >> For ruby and Haskell I also have some code which can create package >> descriptions for dev versions of packages which then can be read by the >> code creating the derivations on the fly. >> >> And then there is stills the question: >> Is it efficient to download 40.000 package descriptions if you need only >> 10? The lazy behaviour of the native package managers for ruby (gem), >> python (eg pip) etc somehow make this question obsolete. >> >> Just think about how many perl packages there are available. >> >> Well - you don't have to download 40.000 packages, cabal2nix only dumps >> the the maintained packages which are selected manually. >> Another solution would be making nix connect to a server to access a >> versioned well known "dump state" about known packages. Then only those >> package infos could be fetched which are required to fullfill would have >> to be fetched. >> >> The ivy case may be not trivial cause you can configure dependencies in >> a transient way which means if you have A < B < C you can configure C to >> modify dependency A or such (I never fully had the time to learn about >> all features). >> >> So the topic is hot - and there is still quite some work left to be >> done. >> >> The cabal2nix way may work well if you need some packages only and is >> easy to understand and to debug. >> >> I hope I was able to shed some light into current state I know about - >> others may know more. >> >> Let's not forgett that eg most xorg packages are generated >> automatically, too. The some additional manual work is required to make >> everything build. >> >> There are more sub universes, such as gnome which is provides a central >> download folder hirarchy you could use to dump package information from. >> Nobody did it yet. >> >> Marc Weber >> _______________________________________________ >> nix-dev mailing list >> nix-dev@lists.science.uu.nl >> http://lists.science.uu.nl/mailman/listinfo/nix-dev > _______________________________________________ > nix-dev mailing list > nix-dev@lists.science.uu.nl > http://lists.science.uu.nl/mailman/listinfo/nix-dev -- Florian Friesdorf <f...@chaoflow.net> GPG FPR: 7A13 5EEE 1421 9FC2 108D BAAF 38F8 99A3 0C45 F083 Jabber/XMPP: f...@chaoflow.net IRC: chaoflow on freenode,ircnet,blafasel,OFTC
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