Tanguy Le Carrour <tanguy@bioneland.org> writes:

> Hi Guix!
>
> I'm working on updating python-pytest and… not everything is going as
> smoothly as I was expecting! :-(
>
> Pytest 5.2.1 depends on Pluggy >=0.12.0… which depends on
> importlib-metadata. But when I had the latter as a propagated-input to
> python-pluggy, then `guix build` gets stuck.
>
>     diff --git a/gnu/packages/python-xyz.scm b/gnu/packages/python-xyz.scm
>     index a7f83dcd31..ab80cdebf9 100644
>     --- a/gnu/packages/python-xyz.scm
>     +++ b/gnu/packages/python-xyz.scm
>     @@ -8914,17 +8914,19 @@ library as well as on the command line.")
>      (define-public python-pluggy
>        (package
>         (name "python-pluggy")
>     -   (version "0.11.0")
>     +   (version "0.13.0")
>         (source
>          (origin
>           (method url-fetch)
>           (uri (pypi-uri "pluggy" version))
>           (sha256
>            (base32
>     -       "10511a54dvafw1jrk75mrhml53c7b7w4yaw7241696lc2hfvr895"))))
>     +       "0d4gsvb4kjqhiqqi4bbsdp7s1xlyl5phibcw1q1mrpd65xia2pzs"))))
>         (build-system python-build-system)
>         (native-inputs
>          `(("python-setuptools-scm" ,python-setuptools-scm)))
>     +   (propagated-inputs
>     +    `(("python-importlib-metadata" ,python-importlib-metadata)))
>         (synopsis "Plugin and hook calling mechanism for Python")
>         (description "Pluggy is an extraction of the plugin manager as used by
>      Pytest but stripped of Pytest specific details.")
>
> The problem seems to be that python-importlib-metadata's dependency graph
> contains… python-pluggy!
>
> How am I supposed to fix this chicken and egg situation?! Is this
> something that should be notified to upstream?!

It would be great if you can make upstream aware of the issue.

Note that if you just want to be able to use Pytest 5.x on the master
branch, you can instead add a separate 'python-pluggy-0.13' variable and
use that for 'python-pytest-5'.

We'll still need to break the cycle in 'core-updates' though...