Getting Unit Test Results Out Of Guix Build

[Phil Beadling <phil@beadling.co.uk>]

Hi all,

Given Guix builds packages in a container, is there any way of getting a
file out of the build container for further processing?

In my use case - I generate some junit test XML output during the build
process and want to render that to a webpage rather than send it to stdout
as part of the build process?

It is possible to export the nar file using guix archive --export, and
possible to keep failed build artifacts using -K, but there doesn't seem to
be a way to dump out a file from a successful build?

Is this against the philosphy of purely-functional builds?  Obviously it is
a side-effect to dump out an XML file, but no more so than sending build
logs to stdout?  Is it possible to dump outputs without breaking
referential transparency on the inputs - i.e. it should be possible to
configure a directory that is write-only for the container, but can be read
by users outside the container?

Or am I missing something obvious?

Thanks,
Phil.