gRPC-haskell/fetch-nixpkgs.nix
2017-12-28 09:41:39 -06:00

51 lines
1.5 KiB
Nix

{ rev # The Git revision of nixpkgs to fetch
, sha256 # The SHA256 of the downloaded data
, system ? builtins.currentSystem # This is overridable if necessary
}:
with {
ifThenElse = { bool, thenValue, elseValue }: (
if bool then thenValue else elseValue);
};
ifThenElse {
bool = (0 <= builtins.compareVersions builtins.nixVersion "1.12");
# In Nix 1.12, we can just give a `sha256` to `builtins.fetchTarball`.
thenValue = (
builtins.fetchTarball {
url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
inherit sha256;
});
# This hack should at least work for Nix 1.11
elseValue = (
(rec {
tarball = import <nix/fetchurl.nix> {
url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
inherit sha256;
};
builtin-paths = import <nix/config.nix>;
script = builtins.toFile "nixpkgs-unpacker" ''
"$coreutils/mkdir" "$out"
cd "$out"
"$gzip" --decompress < "$tarball" | "$tar" -x --strip-components=1
'';
nixpkgs = builtins.derivation {
name = "nixpkgs-${builtins.substring 0 6 rev}";
builder = builtins.storePath builtin-paths.shell;
args = [ script ];
inherit tarball system;
tar = builtins.storePath builtin-paths.tar;
gzip = builtins.storePath builtin-paths.gzip;
coreutils = builtins.storePath builtin-paths.coreutils;
};
}).nixpkgs);
}