[bug#53466] [PATCH] home: Add redshift service.

[Andrew Tropin]

On 2022-02-01 10:15, Ludovic Courtès wrote:

> Hi Andrew,
>
> We’re drifting away from the practical issue of adding a Redshift
> service, but you raise interesting issues.

That's true, but a few first home services will set the tone for the
rest, so it's probably a good idea to look ahead right now, then later.

>
> Andrew Tropin <andrew@trop.in> skribis:
>
> [...]
>
>>> Yes, that’s the usual tradeoff.  The choice made so far in Guix has been
>>> to choose clarity over faithfulness to upstream’s name choices.
>>>
>>
>> Maybe I'm wrong, but it's very likely that most of the users will be
>> checking out upstream documentation anyway during configuration of some
>> programs and those renamings will bring a lot of confusion and
>> especially, when the record fields names will be combined with names in
>> escape hatches.
>
> I think there doesn’t have to be a single answer.  For Redshift and its
> handful of options, I see little incentive to go look at ‘man redshift’;
> it doesn’t add much to what we provide.
>
> For more complex services, the answer might be different, although again
> the Dovecot service shows that, even for this big a service, we can
> provide comprehensive bindings and associated documentation.
>
> [...]
>
>>> I can see the appeal of alists, but the choice made in Guix is to use
>>> records for configuration; that has advantages, such as type checking,
>>> detection of incorrect field names, and the ability to use all the bells
>>> and whistles of (guix records).
>>
>> Type checks are possible with data structure driven approach as well and
>> in a fact it's much more flexible and powerful, however to be fair it
>> will require some work to prepare a good framework for that like
>> https://github.com/plumatic/schema
>> or
>> https://github.com/metosin/spec-tools/blob/master/docs/02_data_specs.md
>> for Clojure.
>>
>> It's also possible to generate documentation for such specs.
>>
>> Potentially, such approach is more powerful.
>
> I’m aware of Clojure specs, but I don’t find it convincing compared to
> records, at least for our use case.
>

Ok.

>>>> It would be good to extend home-files-service-type with config-file
>>>> generated above and home-profile-service-type with the value of
>>>> `redshift` field.
>>>
>>> Regarding the former, that’s not something we usually do for system
>>> services.
>>
>> Imagine terminal or almost any other user space program
>
> I’m not imagining: we’re discussing a very concrete service here.  :-)
>
> For Redshift, I don’t see the point of making the config available
> globally.  For system services, there’s only a handful of exception (PAM
> and OpenSSH come to mind, but see /etc).
>
> Again, there doesn’t have to be a single answer.  I suspect many
> services won’t need to make their config available under ~/.config, but
> if some do, so be it.  I’d say that the default should be to not make
> config available unless that’s required, just like what we do for system
> services.
>
> How does that sound?

It sounds logical for redshift, but inconsistent in general: some home
services install package to profile, some not, some create config in
XDG_CONFIG_DIR, some not.

I still think that almost all services must provide both package and
configs.

>>> As for the latter, I thought about it but I’m not sure what it would be
>>> used for.  WDYT?
>>>
>>
>> It can be used for debugging, for man pages or when redshift don't use
>> shepherd service and started in different way (by wm for example).
>
> The point of this Redshift service is to have it started automatically,
> so to me the only reason to add ‘redshift’ to the user profile would be
> to allow ‘man redshift’.
>
> I don’t view it as super useful in this case, and would instead lean on
> the side of not “polluting” the user’s profile, but I can very well
> imagine that in other cases we’d prefer to extend the user’s profile.
>
>>> I understand your concerns, but I think they’re beyond the scope of this
>>> review.  I also think that there’s ample experience with system services
>>> showing that writing “nice” configuration bindings actually works in
>>> practice.
>>
>> I saw how well-written, but macros-based solutions in Clojure ecosystem
>> slowly died and substituted with data-based.  I understand that Guile
>> ecosystem has a slightly weaker toolkit for processing datastructures,
>> but by the end of the day I think we will be here sooner or later.
>> Using macros instead of datastructures feels for me like remaking the
>
> Records are data structures, not macros.
>

But, IIRC, define-configuration, define-record-type are.

>> same mistake again knowing the consequences.  Maybe I'm wrong.
>
> Maybe one of us is wrong, or maybe it’s more complex than this.  :-)

Also, maybe my non-guile experience doesn't apply here.

>
> As it turns out, I find Guix’s configuration records rather nice to
> use—much nicer than, for example, Gnus’ loose configuration trees.

Unfortunately, I'm not familiar with Gnus internals and can't say if
it's related, similar or not.

-- 
Best regards,
Andrew Tropin

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