gobject-introspection: Conditionalize depsTargetTargetPropagated

[Artturin]

Fixes ↓

nix-repl> pkgsCross.x86_64-freebsd.pkgsBuildHost.gobject-introspection
error: Don't know how to run x86_64-unknown-freebsd executables.

The unwrapped already doesn't error

nix-repl> pkgsCross.x86_64-freebsd.pkgsBuildHost.gobject-introspection-unwrapped
«derivation /nix/store/xq4q4vigy2glmfng2h6bbr4sysyk8ipz-gobject-introspection-1.82.0.drv»

https://www.github.com/NixOS/nixpkgs/blob/7b1cffdd2e13b2cdad5b37e259016efd0ea48fcd/pkgs/development/libraries/gobject-introspection/default.nix#L114

It's caused by depsTargetTargetPropagated = [ overridenTargetUnwrappedGir ]; in the wrapper

In graphene there is
PATH=${python3.withPackages (pp: [ pp.pygobject3 pp.tappy ])}/bin:$PATH patchShebangs tests/introspection.py

Which causes the Don't know error in pkgsCross.x86_64-freebsd.pkgsBuildHost.graphene

because python3 and pygobject3 will be from pkgsHostTarget

and then pygobject3 has gobject-introspection from pkgsHostTarget

and then that gobject-introspection will have pkgsCross.x86_64-freebsd.pkgsCross.x86_64-freebsd.buildPackages.pkgsTargetTarget.gobject-introspection.gobject-introspection in depsTargetTargetPropagated

To test that importing the python library gi works without depsTargetTargetPropagated

let
  pkgs =
    (import ./. {
      crossSystem = (import ./lib).systems.examples.aarch64-multiplatform;
      # On `master` uncomment this and comment `propagatedBuildInputs` below and you'll get
      # error: Don't know how to run x86_64-unknown-freebsd executables.
      #crossSystem = (import ./lib).systems.examples.x86_64-freebsd;
      overlays = [
        (_: prev: {
          pythonPackagesExtensions = prev.pythonPackagesExtensions ++ [
            (_: pprev: {
              pygobject3-test = pprev.pygobject3.overrideAttrs {
                propagatedBuildInputs = [
                  pprev.pycairo
                  (prev.gobject-introspection.overrideAttrs { depsTargetTargetPropagated = [ ]; })
                ];
              };
            })
          ];
        })
      ];
    }).pkgs;
  pyr = pkgs.pkgsBuildHost.python3Packages.python.withPackages (pp: [ pp.pygobject3-test ]);
in
pkgs.pkgsBuildBuild.runCommand "test" { } ''
  "${pyr.interpreter}" -c "import gi" && touch "$out"
''

[philiptaron]

Good golly.

[alyssais]

What's the propagation needed for in the first place?

[Artturin]

What's the propagation needed for in the first place?

nixpkgs/pkgs/development/libraries/gobject-introspection/wrapper.nix

Line 12 in 0ab7357

# a comment for both depsTargetTargetPropagated's

nixpkgs/pkgs/development/libraries/gobject-introspection/wrapper.nix

Line 71 in 0ab7357

# when cross-compiling and using the wrapper then when a package looks up the g_ir_X

We also did it so we have to add gobject-introspection to only one dependency attribute at a time

Yeah its a hack but so far it's been working quite well invisibly.

The girs running by emulator might also have looked for something targetOffset but I do not remember

nixpkgs/pkgs/development/libraries/gobject-introspection/wrapper.nix

Line 61 in 0ab7357

export targetgir="${lib.getDev overridenTargetUnwrappedGir}"