[Nix-dev] [***SPAM***] Proposal: Conditional attribute syntax sugar

[Shea Levy]

Hi Eelco,

On 1/7/12 1:21 PM, Eelco Dolstra wrote:
> I've been thinking about a special ‘ignore’ value:
>
> derivation {
>    CFLAGS = if system == "i686-darwin" then "bla" else ignore;
> }
>
> This value would be like ‘null’, except that if a derivation attribute evaluates
> to ‘ignore’, it wouldn't be added to the environment of the builder.
>

Neat idea. I've attached a patch for a simple implementation of this, 
what do you think? Note that trying to explicitly coerce ignore to 
string will cause an error in this implementation.

Cheers,
Shea
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