Re: (propagated) 'inputs' depends on 'outputs'?

[zimoun]

Bonjour Julien,

On Sat, 13 Jun 2020 at 07:38, Julien Lepiller <julien@lepiller.eu> wrote:

> Exactly, no. You cannot separate inputs from outputs, because they are
> part of the same derivation. When you build an output, you actually
> build the complete derivation and there's no way to separate that in
> "this part builds out" and "this part builds doc", etc.

So it means that I need to build all the outputs even if I am interested
in only one, right?

If I run "guix install foo:out --no-substitutes" then I potentially
build any other "outputs"" of foo, e.g., "doc" i.e., potentially
download a lot of TeX stuff, or in the case of Git, all the Subversion
stuff.  Right?

Even if at the end, only the references used by "foo:out" will be
tracked and all the others potentially garbage collected.  Right?


> It would make sense to only propagate for some outputs: suppose at
> runtime only foo:bin requires the propagation of bar. Since foo and
> bar are already built, it should be possible to restrict the
> propagation behaviour to that output. Foo:out would not bring in bar
> anymore, reducing the closure size.

Yes, it seems making sense to only propagated if the output needs it.
Well, if it is not implemented yet maybe it is because it is not really
necessary. :-)


Thank you for explaining.  It is clearer for me now.

Cheers,
simon