[Nix-dev] variable scope / recursion

[Mathijs Kwik]

Maybe I better explain what I'm trying to achieve.

I have a bunch of packages and overrides that aren't very useful for
others, so I can't commit them to nixpkgs.
I don't want to constantly maintain my own "fork" that I need to keep
up-to-date, but rather use the current "channels" functionality.

So I figured it's easiest to just use packageOverrides to apply the
modifications and to add the additional packages.

This works fine for almost everything, but I want to structure my
additional packages more like nixpkgs itself (use directories and
callPackage). Ideally, I don't want to distinguish between nixpkgs and
my own pkgs, so the scope for callPackage needs to be the composition
of nixpkgs with my own stuff.

But it seems I can't get a reference to the final nixpkgs attrset
within the overrides function...

Any hints?

Thanks,
Mathijs



On Fri, Jul 6, 2012 at 12:10 PM, Mathijs Kwik <mathijs at bluescreen303.nl> wrote:
> On Fri, Jul 6, 2012 at 12:01 PM, Kirill Elagin <kirelagin at gmail.com> wrote:
>> rec is the answer (this is something like let/letrec in Lisp, if you know
>> what I mean ;) ).
>
> I don't see how rec would help here.
> As I understand it, rec helps when an attrset has attributes that
> refer to each other.
> But in this case, bar isn't referring to foo in the same object (the
> overrides object I'm creating, containing just foo and bar), but to
> pkgs.foo.
>
> Anyway, I tried it anyway:
>    packageOverrides = pkgs:
>      rec { foo = "string";
>        bar = pkgs.foo + " concatenation";
>      };
>
> But this does not help.
> Still "missing attribute foo".
>
>
>>
>> --
>> Кирилл Елагин
>>
>>
>> 2012/7/6 Mathijs Kwik <mathijs at bluescreen303.nl>
>>>
>>> Hi all,
>>>
>>> I was reading this interesting piece of all-packages.nix
>>> (comments/whitespace removed):
>>>
>>>   applyGlobalOverrides = overrider:
>>>     let
>>>       overrides = overrider pkgsOrig //
>>>         (lib.optionalAttrs (pkgsOrig.stdenv ? overrides && crossSystem
>>> == null) (pkgsOrig.stdenv.overrides pkgsOrig));
>>>       pkgsOrig = pkgsFun pkgs {};
>>>       pkgs = pkgsFun pkgs overrides;
>>>     in pkgs;
>>>
>>> I'm familiar with tying-the-knot lazy trickery in haskell.
>>> As pkgsOrig uses pkgs (the final end result including overrides), and
>>> the overrider function gets passed pkgsOrig, I would expect the
>>> following to work:
>>>
>>>   packageOverrides = pkgs:
>>>     { foo = "string";
>>>       bar = pkgs.foo + " concatenation";
>>>     };
>>>
>>> However, it complains about foo missing.
>>> What am I missing?
>>>
>>> Thanks,
>>> Mathijs
>>> _______________________________________________
>>> nix-dev mailing list
>>> nix-dev at lists.science.uu.nl
>>> http://lists.science.uu.nl/mailman/listinfo/nix-dev
>>
>>