[Nix-dev] $out in configureFlags is not expanded

[Lluís Batlle i Rossell]

On Tue, May 21, 2013 at 12:57:10PM +0200, Peter Simons wrote:
> Hi Lluís,
> 
>  >> Maybe it would be sufficient to document the current behavior in
>  >> more detail?
>  >
>  > Many people hit this problem, when they started using mkDerivation.
> 
> yes, that is true. I'm just not convinced that changing the semantics of
> configureFlags is the best solution for this issue. IMHO, documentation
> can improve the status quo, too, without requiring an intrusive change
> to the default builder.

Mh I think the manual mainly helps to tell people "please read the manual", when
they ask the question. ;)

>  > Can you describe what breaking cases you have in mind with that 'eval'?
> 
> For example:
> 
>   configureFlags = "--whoami-expression=$USER";
> 
>   configureFlags = "--initial-array=( 'state 1' 'state 5' )";

Are these real cases? :)

> Please don't get me wrong, though: I know that all of those problems can
> be addressed in one way or another, and we probably don't have many
> packages that use such pathological constructs. Still, I'm just not
> convinced that the issue is significant enough to warrant a change to
> the default builder.

Ok; I wouldn't mind the change; I think that few people would expect "$USER" to
not to expand to the env var value, in your first example.

And I'm not sure what would the writer of the 2nd example expect to happen.

Regards,
Lluís.