How does pkgsStatic not clobber overlays/crossOverlays?

Radvendii · April 27, 2021, 4:49pm

If I import nixpkgs with some overlays or crossOverlays set, and then invoke pkgsStatic.something, that’s defined as

github.com

NixOS/nixpkgs/blob/24063d067f434de0d03e8a0f15437ae08b9dc1be/pkgs/top-level/stage.nix#L214-L234


      
            pkgsStatic = nixpkgsFun ({
              overlays = [ (self': super': {
                pkgsStatic = super';
              })] ++ overlays;
              crossOverlays = [ (import ./static.nix) ];
            } // lib.optionalAttrs stdenv.hostPlatform.isLinux {
              crossSystem = {
                isStatic = true;
                parsed = stdenv.hostPlatform.parsed // {
                  abi = {
                    gnu = lib.systems.parse.abis.musl;
                    gnueabi = lib.systems.parse.abis.musleabi;
                    gnueabihf = lib.systems.parse.abis.musleabihf;
                  }.${stdenv.hostPlatform.parsed.abi.name}
                    or lib.systems.parse.abis.musl;
                };
              } // lib.optionalAttrs (stdenv.hostPlatform.system == "powerpc64-linux") {
                gcc.abi = "elfv2";
              };
            });
          };

Which uses nixpkgsFun, which is defined as:

github.com

NixOS/nixpkgs/blob/24063d067f434de0d03e8a0f15437ae08b9dc1be/pkgs/top-level/default.nix#L108


      
          # want the provided non-native `localSystem` argument to affect the stdenv
          # chosen.
          #
          # NB!!! This thing gets its `config` argument from `args`, i.e. it's actually
          # `config0`. It is important to keep it to `config0` format (as opposed to the
          # result of `evalModules`, i.e. the `config` variable above) throughout all
          # nixpkgs evaluations since the above function `config0 -> config` implemented
          # via `evalModules` is not idempotent. In other words, if you add `config` to
          # `newArgs`, expect strange very hard to debug errors! (Yes, I'm speaking from
          # experience here.)
          nixpkgsFun = newArgs: import ./. (args // newArgs);
          
          
# Partially apply some arguments for building bootstraping stage pkgs
          # sets. Only apply arguments which no stdenv would want to override.
          allPackages = newArgs: import ./stage.nix ({
            inherit lib nixpkgsFun;
          } // newArgs);
          
          
boot = import ../stdenv/booter.nix { inherit lib allPackages; };
          
          
stages = stdenvStages {

in top-level/default.nix. Notice that it’s importing itself with args // newArgs, so I would expect the overlays and crossOverlays from pkgsStatic (newArgs) to overwrite any that you passed in to top-level/default.nix through top-level/impure.nix through the default.nix at the base of the github directory (args).

And yet, I’m able to pass in overlays and crossOverlays just fine while using pkgsStatic. How is that happening?

AleXoundOS · November 25, 2021, 9:50am

At least something happens to buildInputs in crossOverlays. They become propagatedBuildInputs when pkgsStatic in use. For example, here super.libwebsockets.overrideAttrs (def: ...) def.propagatedBuildInputs refers to original buildInputs and also you need to override propagatedBuildInputs instead.
This is annoying if you want to have the same overlay for both dynamic and static builds. I have to write:

    propagatedBuildInputs =
      if super.stdenv.hostPlatform.isStatic
      then with self; [ glib openssl ]
      else def.propagatedBuildInputs;
    buildInputs =
      if ! super.stdenv.hostPlatform.isStatic
      then with self; [ glib openssl ]
      else def.buildInputs;

@matthewbauer, maybe I miss something here, is it intended behavior?