On 01-09-2022 11:09, Ludovic Courtès wrote:
>> I guess this is expected, since a change in a build system might affect
>> all packages being built with it. But I was wondering if there is a way
>> to force only building the packages specified on the command line. Does
>> such a thing exists?
> No, it doesn’t exist, because that would be building something
> different.  In this case, building everything that depends on
> ‘ant-build-system.scm’ is unavoidable.
>
>> I was wondering what is the most efficient way to quickly iterate on
>> changes to a build system, without recompiling the whole world for that
>> build system. How would you do that?
> There’s no ideal solution as you’ll have to recompile the world anyway.

It is possible, actually, to test it for a single package first 
(although without interaction with the command line). In the package you 
would like to test things with, use '=>' in #:imported-modules:

((this module)
  ((that module) => (local-file "customised-that-module.scm")))

and keep the original that/module.scm unmodified.

At least, something like that is done in 'build-program' in 
build-aux/build-self.scm -- I haven't tried it out for something like 
this myself.

Greetings,
Maxime