[Nix-dev] variable scope / recursion

[Kirill Elagin]

But the ``__overrides`` will be empty in ``pkgsOrig``!
Those new attributes are not... hmm... actually merged into the attrset,
they still reside in this attribute and "pkgsOrig = pkgsFun pkgs {}"
overwrites everything in __overrides with an empty attrset effectively
removing all your overrides completely.

--
Кирилл Елагин


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

> On Fri, Jul 6, 2012 at 2:28 PM, Kirill Elagin <kirelagin at gmail.com> wrote:
> > 2012/7/6 Mathijs Kwik <mathijs at bluescreen303.nl>
> >>
> >> Yeah I saw those comments too, but I can't see how that would work.
> >> Because the "original" (pkgsOrig) set is built by passing pkgs (the
> >> final set) to pkgsFun.
> >> In other words, the set references itself, which is perfectly normal
> >> in a lazy setting.
> >> The notion of "original" makes sense for the attributes that get
> >> overwritten, but for the rest, I would expect a "shine through".
> >
> >
> > As Shea already pointed out there is ``__overrides`` dark magic involved.
> > Basically, your overrides are never added to pkgs directly, I mean,
> there is
> > no something like "pkgs = overrides // origPkgs".
>
> The documentation clearly states __overrides is more powerful than //,
> because // would leave the original set looking at the old values when
> introspecting itself. With __overrides, they _do_ get added to the
> set, and even replace the items inside, so other items in the set see
> the new values.
>
> So this __overrides magic is indeed why I would expect this to work,
> as it gives a consistent attrset which can look at itself and see the
> (new) consistent view.
>
> >
> > --
> > Кирилл Елагин
> >
>
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