[Nix-dev] variable scope / recursion

[Kirill Elagin]

Yeah, now I get your problem.
It think, it's clear from the source of `applyGlobalOverrides` and from
comments, that your `packageOverrides` is called with _original,
non-overriden_ pkgs. This way you can to refer to _original_ attributes
when overriding them.

I think the only option is to manually simulate overriding process in
`packageOverrides` to obtain overriden pkgs.

--
Кирилл Елагин


2012/7/6 Mathijs Kwik <mathijs at bluescreen303.nl>

> 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
> >>
> >>
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