Re: How to reference external program used in shell-scripts?

[P]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, September 3, 2019 1:01 PM, Ludovic Courtès <address@hidden> wrote:

> Hello Hartmut,
>
> Hartmut Goebel address@hidden skribis:
>
> > My concerns are not about building, but about installing. A concrete
> > example:
> >
> > -   Ansible is a Python program running ssh via a path to
> >     /gnu/store/…-openssh-8.0p1/bin/ssh
> >
> > -   Mary installs ansible.
> > -   Now openssh shows a serious bug and Mary updates openssh using "guix
> >     -u openssh"
> >
> >
> > Obviously this will not update ansible, and ansible will still use the
> > old, vulnerable version of openssh.
> > OTOH, if ansible would run ssh via $PATH, ansible would pick up the new
> > version of openssh.
>
> The whole idea of functional software deployment is that it’s stateless:
> you can tell that /gnu/store/…-ansible-1.2.3 will always behave the
> same, no matter what other programs are available on your machine.
>
> Introducing “dynamic binding” (e.g., looking up programs in $PATH) would
> allow for faster security updates in the example you gave, but that
> would be at the expense of that core property I described above. It
> would be a regression.
>
> I think what we need in this case is (1) fast security updates, which is
> what grafts help us achieve, and (2) documentation that clarifies what
> the deployment model is, such that Mary would know that ‘ansible’ also
> needs to be upgraded in the example above.
>
> Ludo’.

What about the performance side?
Can we tell Guix that an input is runtime only? Or only needed in certain 
stages of the build? Or is that better accomplished by splitting a package?
For example, if a large package (let's say... written in Rust) uses Lua for a 
utility script at run time, but doesn't touch it at build time changing the Lua 
version should not result in a recompilation.