[Nix-dev] Nix dependencies

[Vladimír Čunát]

Hi.

This is a follow-up, but it considers a long-term thoughts of mine about 
nix package management evolution. I'll be glad to read your opinions.

On 01/10/2013 08:26 PM, Vladimír Čunát wrote:
> there are external-runtime dependencies (let me call them that), like
> executables from other packages only run when *executing* something in
> the package (like firefox plugins). These can be added via wrappers, so
> in case the external executables are rebuilt you only need to rebuild
> the wrappers (which is trivial) and not the whole package.

This could also be done with libraries (not used in nixpkgs AFAIK).

Since there might be problems with configure scripts, I would do it this 
way:
  - use the intensional model of the store (we use extensional AFAIK) 
[nix-thesis]
  => the hashes will be the same iff the contents is
  - clear all RPATH records, so rebuilding against another library 
version usually doesn't change the hash (so the path is re-used!)
  - wrap all executables to use exactly the library versions we want. We 
have to cover the whole dependency tree... and as a bonus we can more 
easily check/ensure that there are not multiple library versions in 
dependencies of one executable (that's IMHO mostly undesirable).

[nix-thesis] http://nixos.org/~eelco/pubs/phd-thesis.pdf

I believe something like the way above would be a very nice improvement 
in many aspects:
  - less disk space, perhaps slightly smaller binary patches
  - possibility of impure quick re-linking with security updates 
(without rebuilding) and testing consistency retrospectively by true 
rebuilding
  - perhaps more consistent library sets
  - probably easier purity checking (via content-addressable store)

BTW, a not-so-much-related idea: we could test purity by randomly trying 
to build the same derivation on another machine.


Vlada


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