shepherd GEXP module import mystery

[Attila Lendvai]

dear Guix,

context: i'm adding logging to shepherd, and while i was testing it i 
encountered a conflict with my service code that shouldn't happen.

i'm probably missing something from my mental model around guile modules, 
and/or how shepherd compiles and loads them.

the symptom is that a start GEXP of my service sees bindings that come from the 
module called (shepherd support), but i have no idea who and where imports that 
module.

i added the following two format lines to the beginning of my start GEXP:

(format #t "*** start gexp speaking, current module is ~A, module-uses: ~A~%  
ringbuffer: ~A~%"
  (current-module)
  (module-uses (current-module))
  (and=> (module-variable (current-module) 'ring-buffer) variable-ref))

(format #t "*** ringbuffer in packages: ~A~%"
  (map (lambda (module-name)
         (and=> (module-variable (resolve-interface module-name)
                                 'ringbuffer)
                variable-ref))
       '((guile) (oop goops) (shepherd service) (srfi srfi-34)
         (system repl error-handling) (guix build utils) (guix build syscalls)
         (gnu build file-systems))))

and they print:

*** start gexp speaking,
current module is #<module (#{ g108}#) 7f6a3af34be0>
module-uses: (
#<interface (guile) 7f6a3ade6dc0>
#<interface (oop goops) 7f6a399eac80>
#<interface (shepherd service) 7f6a39489a00>
#<interface (srfi srfi-34) 7f6a399ea8c0>
#<interface (system repl error-handling) 7f6a39489dc0>
#<custom-interface (guix build utils) 7f6a3af34140>
#<interface (guix build syscalls) 7f6a38cd6e60>
#<custom-interface (guix build utils) 7f6a38cd6500>
#<custom-interface (gnu build file-systems) 7f6a38d6a460>
#<interface (gnu system file-systems) 7f6a38d24b40>
#<custom-interface (guix build utils) 7f6a38d6a3c0>
#<custom-interface (gnu build file-systems) 7f6a38d6a320>
#<custom-interface (guix build utils) 7f6a38d6a280>
#<custom-interface (gnu build file-systems) 7f6a38d6a1e0>
#<custom-interface (guix build utils) 7f6a38d6a140>
#<custom-interface (gnu build file-systems) 7f6a38d6a0a0>
#<custom-interface (guix build utils) 7f6a38d6a000>
#<custom-interface (gnu build file-systems) 7f6a38d93f0

  ringbuffer: #<procedure ring-buffer (size)> 

*** ringbuffer in packages: (#f #f #f #f #f #f #f #f) 

how else can a definition (i.e. 'ringbuffer) get into this module without it 
coming from one of the modules in its module-uses list?

i'm pretty sure that it's coming from (shepherd support) because i'm neck deep 
in debugging the original issue: a macro from (shepherd support) overwrote my 
function that errored when it was called at runtime as a function.

i'm also seeing this warning (i.e. my root issue):

WARNING: (#{ g108}#): `log.debug' imported from both (guix-crypto utils) and 
(shepherd support)

i've checked the module list of the gexp, and how guix compiles the .go files 
that are then given to shepherd, and i see nothing obvious. i even looked at 
the source file that gets generated and compiled for the service in question, 
and it doesn't contain any mention of this module.

there are no direct mentions of (shepherd support) in the source, that's why i 
thought maybe something re-exports the entire module, so i checked the presence 
of 'ringbuffer in all the used modules... but it's not in any of them.

could it be a bug in how different versions/instances of guile serialize/load a 
.go file? or could it be due to the module magic in (gnu services shepherd) 
that compiles the shepherd config into a .go file?

i'm out of ideas, any hint is appreciated!

-- 
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“People always find partners [with] exactly the same level of unresolved 
traumas they are at, without any exception. Now the trauma may look 
differently, and how it manifests may look differently, but the degree of 
trauma is always equal, I mean with perfect accuracy. […] And that trauma then 
shows up in the relationship.”
        — Gábor Máté (1944–), 'On The Spot - Az ellenség gyermekei', 48m50s