channels.<nixpkgs>.overlaysBuilder doesn't work if supportedSystems contains more than one architecture

[willruggiano]

Similar to #96, so feel free to close this if you feel it is a duplicate.

I have been trying to move my macOS system to nix-darwin, starting with home-manager for dotfiles and ran into a similar problem as the aforementioned issue when adding a package (which does not export an overlay);

channels.nixpkgs.overlaysBuilder = channels: [
  (final: prev: {
    emanote = inputs.emanote.defaultPackage.${prev.system};
  })
  ...
];

See here for full context.

This results in the same error as #96;

$ nix flake show     
...
error: a 'x86_64-darwin' with features {} is required to build '/nix/store/path/to/some.drv', but I am a 'x86_64-linux' with features {benchmark, big-parallel, kvm, nixos-test}

The error occurs regardless of the current platform, e.g. "x86_64-linux ... but I am a x86_64-darwin" if on macOS

[willruggiano]

I assume that I am just misusing overlaysBuilder and that there is a better way to accomplish what I am doing. I will add that I am fairly new to nix and very new to your library... so "user error" is highly likely :)

[gytis-ivaskevicius]

You seem to be using it as expected, BUT by the looks of things, the last nix update has caused similar issues. Have not looked into it yet

[gytis-ivaskevicius]

Oh right, for time being you can set supportedSystems to single architecture

[willruggiano]

Yeah, that is indeed what I have done to remediate the problem. Thanks for the quick reply!

[gytis-ivaskevicius]

Solution:

diff --git a/flake.lock b/flake.lock
index fb6dd9c..f273f6e 100644
--- a/flake.lock
+++ b/flake.lock
@@ -330,17 +330,17 @@
         "flake-utils": "flake-utils_3"
       },
       "locked": {
-        "lastModified": 1632420560,
-        "narHash": "sha256-8Tsa4Hp/CHCA6J8/E7EODhp75z5N1NBhFiOb3lBv/tI=",
+        "lastModified": 1636207264,
+        "narHash": "sha256-irsZoK5GERTMWgPzy3p1tAFc4JS+ktasvlWTK79Ixjc=",
         "owner": "gytis-ivaskevicius",
         "repo": "flake-utils-plus",
-        "rev": "4b1bcafcfcd78bd36ceabfe3872822ba5c7fcbe8",
+        "rev": "9651c19f895382702a6257c4da08d14a66488782",
         "type": "github"
       },
       "original": {
         "owner": "gytis-ivaskevicius",
-        "ref": "v1.3.0",
         "repo": "flake-utils-plus",
+        "rev": "9651c19f895382702a6257c4da08d14a66488782",
         "type": "github"
       }
     },
diff --git a/flake.nix b/flake.nix
index 5a960c6..6790046 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,7 +3,7 @@

   inputs = {
     nixpkgs.url = github:nixos/nixpkgs/nixpkgs-unstable;
-    utils.url = github:gytis-ivaskevicius/flake-utils-plus/v1.3.0;
+    utils.url = github:gytis-ivaskevicius/flake-utils-plus/9651c19f895382702a6257c4da08d14a66488782; # not yet merged version of fup

     nix.url = github:nixos/nix/master;
     nixos-hardware.url = github:nixos/nixos-hardware;
@@ -32,11 +32,13 @@
             inherit (lib') makeHome mapFilterAttrs mapModules reduceModules mapModulesRec reduceModulesRec;
           });

-        supportedSystems = [ "x86_64-linux" ];
+        supportedSystems = [ "x86_64-darwin" "x86_64-linux" ];
         channelsConfig.allowUnfree = true;

         channels.nixpkgs.overlaysBuilder = channels: [
-          (final: prev: {
+          #(final: prev: nixpkgs.lib.optionalAttrs (prev.system == "x86_64-darwin") {
+          # or
+          (final: prev: nixpkgs.lib.optionalAttrs (!prev.isFakePkgs or false) {
             emanote = inputs.emanote.defaultPackage.${prev.system};
           })
           self.overlay

Will close this issue since I don't think that anything else can be done here. Reopen in case you think I'm wrong