Re: Generic Python packages which don’t work on all architectures

[Ole Streicher <olebole@debian.org>]

Paul Wise <pabs@debian.org> writes:
> On Thu, Jan 21, 2021 at 1:12 PM Ole Streicher wrote:
>
>> This would be a quite flexible and extendible approach to have packages
>> installable only where they work.
>
> There is precedent for this sort of thing in the isa-support source
> package, which fails installation when your CPU doesn't support
> particular ISA extensions like SSE or NEON.
>
> It is a reasonable workaround for now, but the packages using the
> pseudo-packages would still be available, causing confusion when
> people try to install them.

But this is also the case for all packages which implicitly depend on
other packages which are not available on some architectures. This is
not very rare:

 * Python arch:all packages may depend on arch:* Python packages which
   are not available everywhere

 * Packages written in an interpreted language are arch:all, but depend
   on the interpreter and can only installed on archs where the
   interpreter exists (like gnudatalanguage or iraf from my portfolio)

Generally, arch:all packages depend on a lot of architecture dependent
packages, and unless one resolves the whole dependency chain, there is
no way to check whether a package is actually installable.

> It would be better to just not have them available where they aren't
> going to work. I also wonder how multi-arch stuff would interact with
> the pseudo-packages idea.

IMO this is a problem that already exists there and is not
solved. Imagine the following constellation:

 * I have a python3-foo package with arch:all.
 * this depends on python3-foo-obj that exists only for i386.

Now I have a x86_64 machine that gets i386 added. On this machine, I
could install python3-foo (since the dependency is resolvable), but
'import foo' with the x86_64 interpreter would fail.

Best regards

Ole