[Nix-dev] Displaying package parameters

Tobias Pflug tobias.pflug at gmx.net
Sat Mar 5 08:52:44 CET 2016


Nice, I like that!

Sent from my iPhone

> On 29 Feb 2016, at 04:59, Fabian Schmitthenner <nix-dev at schmitthenner.eu> wrote:
> 
> Hi!
> 
> I just wanted to share that I tried displaying package parameters on the
> nixos homepage and the current result can be seen here:
> http://schmitthenner.eu/nixos-homepage/nixos/packages.html.
> 
> When you click on a package, you hopefully see its parameter. This uses
> a heruristic to try to figure out which parameters are packages (and
> thus not displayed) and which are not (and thus displayed) that goes
> roughly as follows:
> 
> - If the parameter is instantiated - either implicitly or explicitly -
> by callPackage, we look at the value and if it's a derivation, or a list
> or attrset set of derivations, or a function it's not displayed
> - Otherwise, it's displayed
> 
> I think there was a discussion about this a short while ago, but I
> couldn't find it.
> 
> Please let me know what you think and if we might want a (more elaborate
> version, e. g. also displaying the value of default arguments that
> aren't changed by callPackage, which requires an other change to nix
> because this info is currently not available, we only know if the
> argument is optional or not afaik) of this on our official website.
> 
> Source code can be found on
> https://github.com/NixOS/nixos-homepage/compare/master...fkz:master
> Technically, I patched nixpkgs customization, so we not only get the
> override... functions, but also the original parameters and the original
> function.
> Furthermore, this uses a patched version of nix which allows catching
> errors inside nix (added a primop __catch) that also seems useful more
> generally (when polished) (see https://github.com/fkz/nix/tree/catch-throw).
> 
> Fabian
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