xyzBuilder = channels: {..} should be replaced with exports = channels: { packages = ...; apps = ...;}

[gytis-ivaskevicius]

I have no idea why fup does not implement just a single builder for everything - but now that I look at it - it's obvious that this would be quite a bit nicer way of handling things.

Possible issues:
Merging logic, it's always has been a pain. Tho if I recall correctly existing mergeAny function should just work out of the box

Expected outcome:

utils.lib.systemFlake {

  exports = channels: { 
    packages = { 
      inherit (channels.nixpkgs) hello coreutils neovim; 
    };
    
    apps = {
      neovim = mkApp {
        drv = channels.nixpkgs.neovim;
        exePath = "/bin/nvim";
      };   
    };

    checks = { 
      inherit (channels.nixpkgs) hello coreutils neovim; 
    };
    # ... etc ...
  };

}

@blaggacao @Pacman99 Looks good?

[blaggacao]

Looks good, let's make it outputs = instead of exports =. The name "exports" was once proposed in the community for rhe non-package-dependent outputs (like modules & overlays)

[gytis-ivaskevicius]

I am definitely open to naming suggestions but i am not sure if outputs is the right word for it since i got a feeling that it will confuse users.
Basically, I'd rather avoid duplicating keyword outputs like so:

{
  # outputs #1
  outputs = { self, utils, nixpkgs}@inputs:
    utils.lib.systemFlake {
      inherit self inputs;
      
      # outputs #2
      outputs = channels: {
        # ...
      };
    };
}

[blaggacao]

Oh true, I havn't seen that coming. Let's stick with "exports", then.

[Pacman99]

Yeah I like it, the interface is much cleaner.
For devos's mkFlake - which we're trying to maintain as a wrapper of systemFlake - we could do something like this:

exports = channels: lib.mergeAny {
  packages = lib.builder.packagesFromOverlaysBuilderConstructor self.overlays channels;
} (otherArguments.exports channels);

Also we should probably rename packagesFromOverlaysBuilderConstructor, and maybe the overlays exporter too.

But we definitely need a different name for this than exports or outputs. I think enough people have read this proposal: NixOS/nix#3843 (comment), for that to be counter-productive. Even though that proposal might not be implemented, we would be directly opposing it by using the exports name that was suggested for non-system based outputs. And as you said, outputs is confusing because of the duplicate naming.

Random ideas:

• systemOutputs
• outputsBuilder
• products

I like outputsBuilder because it has a direct connection to the previous naming.

[gytis-ivaskevicius]

Implemented in #59