meson: cross-compilation breaks when not using callPackage

[lukateras]

Describe the bug

Cross-compilation will break for derivations that depend on Meson unless wrapped in callPackage. Derivations that use callPackage work fine.

To Reproduce

Create default.nix:

let
  pkgs = (import <nixpkgs> {}).pkgsCross.musl64;
in

with pkgs;

stdenv.mkDerivation {
  name = "example";
  nativeBuildInputs = [ meson ninja ];
}

Run nix-build. It will fail with:

error: attribute 'targetPlatform' missing, at /nix/store/jc62lsfijc5qab87yrbi6aag67jd0lr8-source/pkgs/development/tools/build-managers/meson/default.nix:82:17

Which points to:

nixpkgs/pkgs/development/tools/build-managers/meson/default.nix

Line 82 in 8de795e

system = '${targetPackages.stdenv.targetPlatform.parsed.kernel.name}'

Expected behavior

If you modify default.nix to wrap derivation in callPackage, like this, you can successfully cross-compile a package that depends on Meson:

let
  pkgs = (import <nixpkgs> {}).pkgsCross.musl64;
in

with pkgs;

callPackage ({ stdenv, fetchFromGitHub, meson, ninja }: stdenv.mkDerivation {
  name = "example";
  # This can be any Meson project, providing one without deps as an example:
  src = fetchFromGitHub {
    owner = "transumption-unstable";
    repo = "subnetgen";
    rev = "f386dacfb54db2302c0b6905edfd486e94adf42c";
    sha256 = "0szsmzgsrkkm56d37qp9inj06ik71hkn64fnims2wjn9izk3fpq2";
  };
  nativeBuildInputs = [ meson ninja ];
}) {}

Additional context

Seems that targetPackages.stdenv.targetPlatform is missing for pkgsCross.* unless using callPackage. I wonder if it's always true that stdenv.targetPlatform == targetPackages.stdenv.targetPlatform.

Metadata

Reproducible in the latest nixos-unstable:

import (fetchTarball {
  url = "https://github.com/NixOS/nixpkgs/tarball/8d1510abfb592339e13ce8f6db6f29c1f8b72924";
  sha256 = "0i4jscq2qy2vn9kr8ix9gr8ncf9dss24y09jrqhlpcpryi4i98dc";
})

Maintainer information:

attribute: meson
module:

cc @jtojnar @Ericson2314

[symphorien]

This looks like a duplicate of #49526

[lukateras]

Hm, interesting. It might be possible to fix this in isolation, though.

[anna328p]

I am also experiencing this issue.

[Ericson2314]

This is expected. See splice.nix (no link cause on phone sorry). It is evil but I know no alternative other than a big refactor. Without splicing you need to explicitly use pkgs* to take packages from the right package set. There's nothing wrong with that, except that it's possible to forget.

[stale]

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[Ericson2314]

I think this is fixed; stuff still breaks without callPackage because evil splicing, but there's nothing Meson specific about it.