Hi Tristan,
Tristan <[email protected]> writes:
> I want to create a service that listens on an MQTT topic for messages
> (i.e. "pull docker") and runs corresponding commands on the local machine.
> For that to work I need guile-mqtt but I do to not understand how module
> visibility works in Guix.
> Coming from other languages I would assume that imports would check files next
> to the starting point and then bubble up a predefined PATH until it finds some
> module or fails.
> However that is not what I am seeing or at least the shell command is not
> working the way I am expecting to.
> What am I missing?
>
>
> guix shell guile-mqtt -- guile -c "(use-modules (mosquitto client)) (display
> \"Module loaded successfully\n\")"
I think this is one of those things everyone runs into when starting
with Guix. In Guix, there is a concept of search paths, and they are
(typically) attached to specific *programs*. So, in your case, *guile*
knows how to find guile libraries, so you need also add the guile
package to the profile. Compare
--8<---------------cut here---------------start------------->8---
$ guix shell -C guile-mqtt --search-paths
--8<---------------cut here---------------end--------------->8---
with
--8<---------------cut here---------------start------------->8---
$ guix shell -C guile guile-mqtt --search-paths
export
PATH="/gnu/store/5cnjlww82k4w0bd2f6110v8x5mj9afiv-profile/bin${PATH:+:}$PATH"
export
GUILE_LOAD_PATH="/gnu/store/5cnjlww82k4w0bd2f6110v8x5mj9afiv-profile/share/guile/site/3.0${GUILE_LOAD_PATH:+:}$GUILE_LOAD_PATH"
export
GUILE_LOAD_COMPILED_PATH="/gnu/store/5cnjlww82k4w0bd2f6110v8x5mj9afiv-profile/lib/guile/3.0/site-ccache:/gnu/store/5cnjlww82k4w0bd2f6110v8x5mj9afiv-profile/share/guile/site/3.0${GUILE_LOAD_COMPILED_PATH:+:}$GUILE_LOAD_COMPILED_PATH"
--8<---------------cut here---------------end--------------->8---
There is a similar gotcha with the SSL certificates:
--8<---------------cut here---------------start------------->8---
$ guix shell -NC guile -- guile -c '(pk ((@ (web client)
x509-certificate-directory)))'
;;; ("/etc/ssl/certs")
$ guix shell -NC guile nss-certs -- guile -c '(pk ((@ (web client)
x509-certificate-directory)))'
;;; ("/etc/ssl/certs")
$ guix shell -NC guile nss-certs curl -- guile -c '(pk ((@ (web client)
x509-certificate-directory)))'
;;; ("/gnu/store/qbs8fbv9m0m456p717zkqjxlgmfjam7h-profile/etc/ssl/certs")
--8<---------------cut here---------------end--------------->8---
Notice how the file name of the certificates changes only after the
`curl' package is added to the profile. Neither `guile' nor `nss-certs'
has the search path for them, so it if often necessary to add `curl'
even when you do not plan to use it.
Hope this helps,
Tomas
--
There are only two hard things in Computer Science:
cache invalidation, naming things and off-by-one errors.
