bug#22990: Grafts leads to inefficient substitute info retrieval

[Ludovic Courtès]

David Craven <address@hidden> skribis:

>> On second thought, the whole idea of applying grafts on the final result
>> (instead of applying grafts at each step like we do now) doesn’t fly.
>> It works well for things like a profile or the system derivation, but
>> breaks for less trivial things.
>
>> For example, if you’re building a VM image or a binary tarball, you
>> really need to graft packages early on; trying to graft the VM image or
>> binary tarball wouldn’t have the desired effect.
>
> Isn't a system derivation or a profile derivation an intermediate step
> to these derivations?

Yes, you’re right.  However the implementation I had come up with relied
on “build continuations”, which only worked for the “top-level”
derivations (those you pass to ‘build-derivations’.)

> Can't there be a flag or something called #:already-grafted? #t?

Yeah, we need something like that.  I need to chew a bit more on this to
find a nice way to achieve that.

Thanks for your feedback, I feel less lonely now.  :-)

Ludo’.