bug#54350: Profile collisions in "guix shell"

[Suhail]

Hello Guix,

I came across this issue the other day when attempting to create a
profile that could act as a development environment for Guix. In
addition to noting my observations below, I'd like to understand why
there are collisions in a *new* profile tasked with installing the
dependencies of guix?  Is this a bug?

The [documentation] notes the below command to start "a new shell where
all the dependencies and appropriate environment variables are set up to
hack on Guix":

#+begin_src sh
  guix shell -D guix -CPW
#+end_src

Using guix-shell to export the manifest corresponding to the above one
gets:

#+header: :tangle ./manifest.scm
#+begin_src scheme
  ;; What follows is a "manifest" equivalent to the command line you gave.
  ;; You can store it in a file that you may then pass to any 'guix' command
  ;; that accepts a '--manifest' (or '-m') option.
  (package->development-manifest
    (specification->package "guix"))
#+end_src

Saving the above to manifest.scm and evaluating the below:

#+begin_src sh
  mkdir -p ${GUIX_EXTRA_PROFILES}/guix-build-2
  guix package -p ${GUIX_EXTRA_PROFILES}/guix-build-2/guix-build-2 -m 
./manifest.scm
#+end_src

Results in the following error:

#+begin_example
  ...
  guix package: error: profile contains conflicting entries for bzip2
  guix package: error:   first entry: bzip2@1.0.8 
/gnu/store/4jkvfh9hp9zf9plrcw490ci6vpvc033d-bzip2-1.0.8
  guix package: error:   second entry: bzip2@1.0.8 
/gnu/store/0ngy7fmrp9g3q35wwccnjxzaaqq9f8wi-bzip2-1.0.8
  hint: You cannot have two different versions or variants of `bzip2' in the 
same profile.
#+end_example

Adding --allow-collisions to match guix-shell behaviour makes the
installation succeed, as expected.

[documentation]: 
<https://guix.gnu.org/en/manual/devel/en/guix.html#Building-from-Git>

-- 
Suhail

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