Contents 1 derivation styles 2 verbose style 3 with style 4 rescuing with style 5 get-args-in-file 1 6 get-args-in-file 2 7 string-with-deps-style 8 composableDerivation

edit derivation styles

Telling you about the different styles which can be used to pass dependency to a derivation.

There has been lots of discussion about which style is best. It also tries to list advantages and disadvantages. (TODO: add your comments)

General items to be considered:

(I) code duplication (never write something twice)

(II) static checking. If you syntax check all-packgages.nix

 many missing or illtyped names are caught.

Note: I gave them names so that we can talk about them more easily.

edit verbose style

pro: faster to evaluate. con: you have to wirite the name of dependency once more.

all-packages.nix:

  [...]
  package = import path {
    inherit fetchurl stdenv depA depB;
  }
  [...]

path/default.nix:

  { stdenv, fetchurl
  , depA, depB}: # << superfluous duplication

  stdenv.mkDerivation {

    buildInputs = [depA depB];

    [...]
  }

edit with style

pro: no duplication of dependencies

con: its sayed to make evaluation slower

Marc Weber likes it because its fast to write and easy to maintain for simple packages.

all-packages.nix:

  same as "verbose style"

path/default.nix:

  args: with args;

  stdenv.mkDerivation {

    buildInputs = [depA depB];

    [...]
  }

edit rescuing with style

How can the with style be rescued? Does this make evaluation faster again? Now a. is duplicated. But that's trivial.

all-packages.nix:

   same as "verbose style" or "with style"

path/default.nix:

  a@{...}:

  stdenv.mkDerivation {

    buildInputs = [a.depA a.depB];

    [...]
  }

edit get-args-in-file 1

This was introduced by Yury G. Kudryashov

Subject: [Nix-dev] another style proposal
Date: Sat, 03 Apr 2010 13:01:49 +0400

pro/con: no duplication in all-packgaes.nix (see (II) )

all-packages.nix:

  mypkg = makeOverridable (import ../path/to/mypkg) ( pkgs // { cg =
  getPkgConfig "mypkg"; } );

path/default.nix:

  a:
  let
    inherit (a) stdenv fetchurl other things cg; # << duplication as in "verbose style"
    inherit (a.gtkLibs) gtk glib;
  in

  stdenv.mkDerivation {
    buildInputs = if cg "gtk" false then [ gtk glib ] else [];
  }

edit get-args-in-file 2

This was proposed by Eelco Dolstra in Nix commit -r 17160

pro/con: no duplication in all-packgaes.nix (see (II) )

all-packages.nix:

  foo = callPackage (import ./foo.nix) { };

path/default.nix:

  args: with args;

  or

  {arg1, arg2, ...}:

comments taken from commit -r :17160

 - Use "args: with args;" in the package's function definition.
   This however obscures the actual expected arguments of a
   function, which is very bad.

 - Use "{ arg1, arg2, ... }:" in the package's function definition
   (i.e. use the ellipis "..." to allow arbitrary additional
   arguments), and then call the function with all of "pkgs" as an
   argument.  But this inhibits error detection if you call it with
   an misspelled (or obsolete) argument.

Mail by Eelco giving more details

edit string-with-deps-style

I'm not sure this style can even be compared against the others. It's defining a customizable builder. There are many examples. Watch out for builderDefsPackage in all-packages.nix to find those examples.

edit composableDerivation

This is similar. It tries to make the default derivation customaziable adding a way to define build options. It automatically passes dependencies or adds configuration options..

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