Subject: Re: bug#53676: [PATCH 0/5] *** PulseAudio service improvements ***

From: Liliana Marie Prikler <[email-masked]>
Date: Sun, 06 Feb 2022 10:07:38 +0100

Hi Maxim,

Am Sonntag, dem 06.02.2022 um 01:30 -0500 schrieb Maxim Cournoyer:
> > > With the proposed 'extra-script-files', I'd argue that appending
> > > something to default.pa should be considered an anti-pattern; as
> > > the new field would be the more natural option to *extend*
> > > 'default.pa' (and having a field to override default.pa is still
> > > useful if you don't like any of the default behavior).
> > I don't think you're making a good case here.  Why do you want
> > appending to default.pa to be an anti-pattern?
> 
> Basically, to keep things as simple as they can be.  I'm expecting
> that extending the default.pa file must be a more common use case
> than hacking it up, justifying the 'extra-script-files' simple entry
> point catered for this use case.  Compare:
> 
> --8<---------------cut here---------------start------------->8---
> (script-file (computed-file "default.pa"
>                             #~(begin
>                                 (copy-file #$(file-apend pulseaudio
> "/etc/default.pa")
>                                            #$output)
>                                 (call-with-port
>                                   (open-file #$output "a")
>                                     (lambda (port)
>                                       (format port "~%\
> set-card-profile alsa_card.pci-0000_01_01.0 output:analog-surround-
> 40+input:analog-mono
> set-default-source alsa_input.pci-0000_01_01.0.analog-mono
> set-default-sink alsa_output.pci-0000_01_01.0.analog-surround-
> 40~%"))))))
> --8<---------------cut here---------------end--------------->8---
> 
> to:
> 
> --8<---------------cut here---------------start------------->8---
> (extra-script-files
>   (list (plain-file "configure-audigy-card"
>           (string-append "\
> set-card-profile alsa_card.pci-0000_01_01.0 output:analog-surround-
> 40+input:analog-mono
> set-default-source alsa_input.pci-0000_01_01.0.analog-mono
> set-default-sink alsa_output.pci-0000_01_01.0.analog-surround-40\n"))))
> --8<---------------cut here---------------end--------------->8---

to:

--8<---------------cut here---------------start------------->8---
(script-file 
  (mixed-text-file "default.pa"
                   ".include"
                   ;; (pulseaudio-configuration-script-file service)
                   (file-append pulseaudio "/etc/default.pa")
                   "
set-card-profile alsa_card.pci-0000_01_01.0
output:analog-surround-40+input:analog-mono
set-default-source alsa_input.pci-0000_01_01.0.analog-mono
set-default-sink
alsa_output.pci-0000_01_01.0.analog-surround-40\n"))
--8<---------------cut here---------------end--------------->8---

which yields

--8<---------------cut here---------------start------------->8---
.include /gnu/store/7xwgz4bavb1i8sfx1lm55hlrr3ngjkdx-pulseaudio-
15.0/etc/default.pa
set-card-profile alsa_card.pci-0000_01_01.0
output:analog-surround-40+input:analog-mono
set-default-source alsa_input.pci-0000_01_01.0.analog-mono
set-default-sink
alsa_output.pci-0000_01_01.0.analog-surround-40
--8<---------------cut here---------------end--------------->8---

> The later seems simpler, especially for someone starting with Guix and
> not very familiar with Guile and G-expressions.
That's because you're (intentionally or otherwise) not making a fair
comparison.  The way I wrote above is the way I intended pulseaudio-
service-type to be used and it's in terms of writing the pulseaudio
configuration not that much harder than what you are proposing.  It'd
be trivial to add a clause to ".include /etc/pulse/default.pa.d"
through the service configuration layer.  Also with pulseaudio < 15.0,
you could – after groking gexps a little – produce 

--8<---------------cut here---------------start------------->8---
.include /gnu/store/7xwgz4bavb1i8sfx1lm55hlrr3ngjkdx-pulseaudio-
15.0/etc/default.pa
.include /gnu/store/12345678901234567890123456789012-audigy-card.pa
.include /gnu/store/12345678901234567890123456789013-other-stuff.pa
[...]
--8<---------------cut here---------------end--------------->8---

inside that mixed-text-file.  With pulseaudio 15.0, you can also

(define my-pulseaudio-extra-config
  (directory-union ...))

and use it like

--8<---------------cut here---------------start------------->8---
(script-file 
  (mixed-text-file "default.pa"
                   ".include"
                   (file-append pulseaudio "/etc/default.pa")
                   ".include" my-pulseaudio-extra-config))
--8<---------------cut here---------------end--------------->8---

> > I still don't agree that that's a good idea, however. 
> > Particularly, it would lead to including files from an "old distro"
> > that was infected with Guix when that probably wasn't asked for. 
> > If at all enabled, I'd prefer if pulseaudio-service-type magically
> > inserted that snippet for configurations that add files to
> > default.pa.d.
> 
> There are pros and cons; people might be find it handy that a
> Guix-installed pulseaudio also honors their user scripts living under
> /etc/pulse/default.pa.d.  It seems low risk to me; not worth the
> extra complexity in my opinion.
Note that you are introducing extra complexity to create that directory
from pulseaudio-service-type.  In particular, I don't see how your
solution is a notable improvement over mixed-text-file, which to me
seems better suited towards this purpose.

Cheers