nixpkgs/pkgs/lib/customisation.nix

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let lib = import ./default.nix;
inherit (builtins) getAttr attrNames isFunction;
in
rec {
/* `overrideDerivation drv f' takes a derivation (i.e., the result
of a call to the builtin function `derivation') and returns a new
derivation in which the attributes of the original are overriden
according to the function `f'. The function `f' is called with
the original derivation attributes.
`overrideDerivation' allows certain "ad-hoc" customisation
scenarios (e.g. in ~/.nixpkgs/config.nix). For instance, if you
want to "patch" the derivation returned by a package function in
Nixpkgs to build another version than what the function itself
provides, you can do something like this:
mySed = overrideDerivation pkgs.gnused (oldAttrs: {
name = "sed-4.2.2-pre";
src = fetchurl {
url = ftp://alpha.gnu.org/gnu/sed/sed-4.2.2-pre.tar.bz2;
sha256 = "11nq06d131y4wmf3drm0yk502d2xc6n5qy82cg88rb9nqd2lj41k";
};
patches = [];
});
For another application, see build-support/vm, where this
function is used to build arbitrary derivations inside a QEMU
virtual machine. */
overrideDerivation = drv: f:
let
# Filter out special attributes.
drop = [ "meta" "passthru" "outPath" "drvPath" "hostDrv" "buildDrv" "type" "override" "deepOverride" "origArgs" "drvAttrs" "outputName" "all" "out" ]
# also drop functions such as .merge .override etc
++ lib.filter (n: isFunction (getAttr n drv)) (attrNames drv);
attrs = removeAttrs drv drop;
newDrv = derivation (attrs // (f drv));
in newDrv //
{ meta = if drv ? meta then drv.meta else {};
passthru = if drv ? passthru then drv.passthru else {};
};
# usage: (you can use override multiple times)
# let d = makeOverridable stdenv.mkDerivation { name = ..; buildInputs; }
# noBuildInputs = d.override { buildInputs = []; }
# additionalBuildInputs = d.override ( args : args // { buildInputs = args.buildInputs ++ [ additional ]; } )
makeOverridable = f: origArgs:
let
ff = f origArgs;
in
if builtins.isAttrs ff then (ff //
{ override = newArgs:
makeOverridable f (origArgs // (if builtins.isFunction newArgs then newArgs origArgs else newArgs));
deepOverride = newArgs:
makeOverridable f (lib.overrideExisting (lib.mapAttrs (deepOverrider newArgs) origArgs) newArgs);
})
else ff;
deepOverrider = newArgs: name: x: if builtins.isAttrs x then (
if x ? deepOverride then (x.deepOverride newArgs) else
if x ? override then (x.override newArgs) else
x) else x;
/* Call the package function in the file `fn' with the required
arguments automatically. The function is called with the
arguments `args', but any missing arguments are obtained from
`autoArgs'. This function is intended to be partially
parameterised, e.g.,
callPackage = callPackageWith pkgs;
pkgs = {
libfoo = callPackage ./foo.nix { };
libbar = callPackage ./bar.nix { };
};
If the `libbar' function expects an argument named `libfoo', it is
automatically passed as an argument. Overrides or missing
arguments can be supplied in `args', e.g.
libbar = callPackage ./bar.nix {
libfoo = null;
enableX11 = true;
};
*/
callPackageWith = autoArgs: fn: args:
let f = if builtins.isFunction fn then fn else import fn; in
makeOverridable f ((builtins.intersectAttrs (builtins.functionArgs f) autoArgs) // args);
}