urbit/nix/nixcrpkgs/make_derivation.nix

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env: attrs:
let
nixpkgs = env.nixpkgs;
native_inputs =
(attrs.native_inputs or [])
++ env.default_native_inputs;
cross_inputs = (attrs.cross_inputs or []);
path_join = builtins.concatStringsSep ":";
path_map = dir: inputs: (map (i: "${i}" + dir) inputs);
# We can't just set PATH in our derivation because nix-shell will make the
# derivation's PATH override the system PATH, meaning we can't use utilities
# like "git" or "which" form the host system. So we set _PATH instead, and we
# use a setup script ($setup) that copies _PATH to PATH. And we provide
# $stdenv/setup so that nix-shell can find our setup script.
#
# nixcrpkgs does not expose its users to this mess. The user can specify a
# PATH if they want, and it will be automatically moved to _PATH in the
# derivation.
filtered_attrs = nixpkgs.lib.filterAttrs (n: v: n != "PATH") attrs;
path_attrs = {
_PATH = path_join (
(if attrs ? PATH then [attrs.PATH] else []) ++
(path_map "/bin" native_inputs)
);
};
default_attrs = {
system = builtins.currentSystem;
SHELL = "${nixpkgs.bashInteractive}/bin/bash";
setup = ./pretend_stdenv/setup;
# This allows nix-shell to find our setup script.
stdenv = ./pretend_stdenv;
PKG_CONFIG_PATH = path_join (
(if attrs ? PKG_CONFIG_PATH then [attrs.PKG_CONFIG_PATH] else []) ++
(path_map "/lib/pkgconfig" native_inputs)
);
};
cross_attrs = if !env.is_cross then {} else {
NIXCRPKGS = true;
inherit (env) host arch os exe_suffix;
inherit (env) cmake_toolchain;
PKG_CONFIG_CROSS_PATH = path_join (
(if attrs ? PKG_CONFIG_CROSS_PATH then [attrs.PKG_CONFIG_CROSS_PATH] else []) ++
(path_map "/lib/pkgconfig" cross_inputs)
);
CMAKE_CROSS_PREFIX_PATH = path_join (
(if attrs ? CMAKE_CROSS_PREFIX_PATH then [attrs.CMAKE_CROSS_PREFIX_PATH] else []) ++
cross_inputs
);
};
name_attrs = {
name = (attrs.name or "package")
+ (if env.is_cross then "-${env.host}" else "");
};
builder_attrs =
if builtins.isAttrs attrs.builder then
if attrs.builder ? ruby then
{
builder = "${nixpkgs.ruby}/bin/ruby";
args = [attrs.builder.ruby];
}
else
attrs.builder
else
rec {
builder = "${nixpkgs.bashInteractive}/bin/bash";
args = ["-ue" attrs.builder];
};
drv_attrs = default_attrs // cross_attrs
// filtered_attrs // name_attrs // builder_attrs // path_attrs;
in
derivation drv_attrs