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

[Andrew Tropin]

On 2022-02-07 00:13, Ludovic Courtès wrote:

> Hi Andrew,
>
> Andrew Tropin <andrew@trop.in> skribis:
>
>> The current implementation of escape hatch doesn't work (I can't set
>> missing options in redshift section, because extra-content added after
>> manual section begins, and I'm not sure if redshift's ini parser allows
>> to define a section with the same name a few times, Git for example
>> allows to do so, but it's more an exception).  There are a few ways to fix 
>> it:
>>
>> 1. Move manual section on top of redshift section, so the extra-content
>> will be added just after redshift section
>> 2. Move extra-content before manual section to accoplish the same.
>> 3. Use file escape hatch (as it done in some system services), which
>> will invalidate all the options set before and just place the content of
>> file field as a value of configuration.
>> 4. Provide the bindings for other options (probably what you were asking).
>
> Ah got it.  I went for #2 and #4 (there are still missing options, but
> we can add them when people actually need them.)
>
> Pushed as 39e8025d3b40a0079f75e0ce9a91b6dad6766773.
>

Good, thank you for working on this!)

>>> How does NixOS handle escape hatches today?  Back when I was using it is
>>> that it wasn’t any more consistent than what we have today, which is at
>>> least a consolation.
>>
>> I don't remember, how it's done for nixos "system modules", but in
>> home-manager it's relatively consistent, in most cases it just a nested
>> maps (attrsets, a little more high-level analogue of alists):
>> https://rycee.gitlab.io/home-manager/options.html#opt-programs.git.extraConfig
>> https://rycee.gitlab.io/home-manager/options.html#opt-accounts.email.accounts._name_.msmtp.extraConfig
>> https://rycee.gitlab.io/home-manager/options.html#opt-gtk.gtk3.extraConfig
>>
>> Sometimes, it allows to add a multi-line string to the end of the file:
>> https://rycee.gitlab.io/home-manager/options.html#opt-programs.abook.extraConfig
>>
>> but it's getting deprecated, when proper serializer for target config
>> format is implemented:
>> https://github.com/nix-community/home-manager/blob/master/modules/programs/git.nix#L342
>>
>> As you can see, they provide a list of frequently used options as
>> top-level "fields", but all of them, including extraConfig just extends
>> (get merged) to primary "config" (iniContent for git for example) and
>> after that, this primary "config" attributeset get serialized to the
>> target config file.  While they have this "escape hatch", it works the
>> same way as all other fields with the only difference: it doesn't have
>> schema (just untyped attributeset).  This is quite close to what we do
>> in rde.
>
> OK, I see.  Nix is all about attribute sets, which are dictionaries,
> like alists, and just as sloppy: you can add attributes but they may or
> may not be ignored, you never know.  Here they “take advantage” of that,
> IIUC, by serializing attributes that happen to be here.
>
> Nix (the language) doesn’t have the ability to define disjoint types
> like what we’re doing with configuration record types, and to me that’s
> a weakness that directly affects usability.
>
> Thanks,
> Ludo’.

-- 
Best regards,
Andrew Tropin

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