[Nix-dev] Accessing files in derivations.

[Guillaume Maudoux (Layus)]

Le 20/04/16 08:59, Vladimír Čunát a écrit :
> On 04/19/2016 10:03 PM, Layus wrote:
>> But your description made me think of a viable workaround.
>> We could ensure that every derivation has a fixed set of known outputs,
>> like dev, lib, out and man.
>> If there is no "lib" output, then the lib attribute could be an alias
>> for out.
> Yes, that has been suggested already and it's the current longer-term
> plan, at least as I see it. It requires nontrivial code rewrite, due to
> $outputLib and similar needing to be selected during evaluation and not
> during build.
>
> --Vladimir
If providing default outputs is just a question of symlinking attributes
to existing derivations, the following (pseudo)code would do, right ?

let
  selectFirst = drv: attrs:
    if (empty attrs) then drv else
      if set ? (head attrs) then set.(head attrs) else selectFirst (tail
attrs);
  wrapDerivation = drv: {                            
    out = selectFirst drv ["out"];
    dev = selectFirst drv ["dev" "out"];
    man = selectFirst drv ["man" "out"];
    lib = selectFirst drv ["lib" "dev" "out"];
    devdoc = selectFirst drv ["dev" "man" "out"];
  } // drv;
in
  mkDerivarion = drv: wrapDerivation (oldMkDerivation drv);

-- Layus.