In reply to @llakala:matrix.org
repl-overlays was actually originally proposed as a cppnix feature and got bikeshedded by roberth and others for not being flakey enough

Hey, I don't understand why a nix-store -qR --include-outputs on a deriver does not include the outputs of dependencies.
Could you help me understand what's happening and if that's the expected behavior?

Basically, the question is why does the last command not contains the output of bison (only the deriver)?

$ nix-instantiate --eval https://releases.nixos.org/nixos/25.11-small/nixos-25.11.8880.5a035534a428/nixexprs.tar.xz -A hello.drvPath --raw
/nix/store/0a8f9vx5sdwdx4a27axfkkjznj5navrq-hello-2.12.2.drv
$ nix-store -q -R --include-outputs /nix/store/0a8f9vx5sdwdx4a27axfkkjznj5navrq-hello-2.12.2.drv | grep bison
/nix/store/vgjfnqbxgxa8a5575bhq07nm35b2l31m-bison-3.8.2.tar.gz.drv
/nix/store/i7miyh7832lkyy229nipb5h6zg5n32rc-bison-3.8.2.drv

Does that even make sense to have a dependency on a deriver but not on its output?

I tried to write a small reproducer (with no dependencies on nixpkgs), but I failed to reproduce:

let
  system = "x86_64-linux";
  # just a basic C program that outputs whatever is in $myRefs env var to $out env var
  builder = ./basic_builder;
in rec {
  a = derivation {
    inherit system builder;
    name = "a";
  };
  b = derivation {
    inherit system builder;
    name = "b";
    myRefs = [ a ]; # $myRefs is written by the builder in the output (so they are run-time deps only?)
  };
  c = derivation {
    inherit system builder;
    name = "c";
    myFakeRefs = [ b ]; #myFakeRefs are not used by the builder, (so they are build-time deps only?)
  };
}

And I get that result:

$ nix-store -q -R --include-outputs "$(nix-instantiate --eval --raw -A c.drvPath)"
/nix/store/bdv4b4s9wryp2cd951x276z17s7v1pi3-basic_builder
/nix/store/1rai7c3259jzzc9qj8jbs0yfwk1c6amx-a.drv
/nix/store/c4f5rm2pchf5b1vri68rpa2in03rnlwg-a
/nix/store/whfq9h0h0blyawwq0nd1qnsyagzm3nli-b.drv
/nix/store/gfs6f7kxal5a52ikndfq8fvfpmx0vz08-c.drv
/nix/store/ircx9amlbg2wlxycrcnsv76cv95fx8g1-b
/nix/store/m6gaqy1fh5hkmlippb5cxjx4l6a7ha98-c