When calling `callPackage`, does `callPackageWith` get evaluated using the initial imported Nixpkgs set?

toraritte · August 18, 2024, 11:30am

For example, in this snippet,

nix-repl> pkgs = import <nixpkgs> {}
nix-rep> pkgs.callPackage ( x: x ) {}

the last call will roughly become

pkgs.lib.callPackageWith <Nixpkgs_subset> ( x: x ) {}

My intuition tells me that the <Nixpkgs_subset> that callPackageWith will be called with is based on the same Nixpkgs set imported at the top (i.e., pkgs). Is this correct?

I will eventually sit down with pen and paper to write out what happens exactly during the 2 calls (i.e., the import and the callPackage one), because I have all the pieces right now, but the endless recursive function calls and Nix laziness keeps throwing me off.

waffle8946 · August 18, 2024, 11:33am

callPackageWith comes from lib, not pkgs.

github.com

NixOS/nixpkgs/blob/bda6ce0df9f508d326d71b16b398c6878908a79a/lib/customisation.nix#L163-L211


      
          /**
            Call the package function in the file `fn` with the required
            arguments automatically.  The function is called with the
            arguments `args`, but any missing arguments are obtained from
            `autoArgs`.  This function is intended to be partially
            parameterised, e.g.,
          
          
    ```nix
              callPackage = callPackageWith pkgs;
              pkgs = {
                libfoo = callPackage ./foo.nix { };
                libbar = callPackage ./bar.nix { };
              };
              ```
          
          
  If the `libbar` function expects an argument named `libfoo`, it is
            automatically passed as an argument.  Overrides or missing
            arguments can be supplied in `args`, e.g.
          
          
    ```nix

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waffle8946 · August 18, 2024, 11:37am

I’m not 100% sure what you were asking originally btw, but you may find this helpful:
https://nix.dev/tutorials/callpackage