lix/tests/lang/eval-okay-functionargs.exp.xml

<?xml version='1.0' encoding='utf-8'?>
<expr>
  <list>
    <string value="stdenv" />
    <string value="fetchurl" />
    <string value="aterm-stdenv" />
    <string value="aterm-stdenv2" />
    <string value="libX11" />
    <string value="libXv" />
    <string value="mplayer-stdenv2.libXv-libX11" />
    <string value="mplayer-stdenv2.libXv-libX11_2" />
    <string value="nix-stdenv-aterm-stdenv" />
    <string value="nix-stdenv2-aterm2-stdenv2" />
  </list>
</expr>
* Two primops: builtins.intersectAttrs and builtins.functionArgs. intersectAttrs returns the (right-biased) intersection between two attribute sets, e.g. every attribute from the second set that also exists in the first. functionArgs returns the set of attributes expected by a function. The main goal of these is to allow the elimination of most of all-packages.nix. Most package instantiations in all-packages.nix have this form: foo = import ./foo.nix { inherit a b c; }; With intersectAttrs and functionArgs, this can be written as: foo = callPackage (import ./foo.nix) { }; where callPackage = f: args: f ((builtins.intersectAttrs (builtins.functionArgs f) pkgs) // args); I.e., foo.nix is called with all attributes from "pkgs" that it actually needs (e.g., pkgs.a, pkgs.b and pkgs.c). (callPackage can do any other generic package-level stuff we might want, such as applying makeOverridable.) Of course, the automatically supplied arguments can be overriden if needed, e.g. foo = callPackage (import ./foo.nix) { c = c_version_2; }; but for the vast majority of packages, this won't be needed. The advantages are to reduce the amount of typing needed to add a dependency (from three sites to two), and to reduce the number of trivial commits to all-packages.nix. For the former, there have been two previous attempts: - 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. 2009-09-15 13:01:46 +00:00			`<?xml version='1.0' encoding='utf-8'?>`
			`<expr>`
			`<list>`
			`<string value="stdenv" />`
			`<string value="fetchurl" />`
			`<string value="aterm-stdenv" />`
			`<string value="aterm-stdenv2" />`
			`<string value="libX11" />`
			`<string value="libXv" />`
			`<string value="mplayer-stdenv2.libXv-libX11" />`
			`<string value="mplayer-stdenv2.libXv-libX11_2" />`
			`<string value="nix-stdenv-aterm-stdenv" />`
			`<string value="nix-stdenv2-aterm2-stdenv2" />`
			`</list>`
			`</expr>`