unofficial mirror of bug-guix@gnu.org 
 help / color / mirror / code / Atom feed
From: Attila Lendvai <attila@lendvai.name>
To: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Cc: 56799@debbugs.gnu.org, "Ludovic Courtès" <ludo@gnu.org>
Subject: bug#56799: (gnu services configuration) usage of *unspecified* is problematic
Date: Thu, 11 Aug 2022 10:15:43 +0000	[thread overview]
Message-ID: <sbyTY2P3pKhHq9Rm0XBEy9BqxoAn8jgZzaEI4IZgtAFHZJQ50UJgVFs2ha7iRsGpiZ4Z7c0wyhuvk2_AmgllEIfFAEpizVKU00HEnWirAoQ=@lendvai.name> (raw)
In-Reply-To: <878rnwn5i4.fsf@gmail.com>

> OK, I've reread this, and it is indeed a risk, that 'unset could leak in
> the case of a serializable configuration making use of a maybe-value
> field of type maybe-symbol. I've added the unit test suggested as
> 97cb43e732a38758c95b7caf3963507188d011cf (currently marked as 'expected
> to fail'). Luckily no current service uses that.

thank you for that Maxim!

and sorry for my initial, somewhat reactive, and emotionally driven response earlier! maintaining a channel with complex services, and finally getting the changes i needed merged into Guix proper was a source of frustration for me.

i've looked at the current state of the code, and it looks good to me. the only issues i have left are the following:

1) the (eq 'unset ...) scattered around the code; it should be hidden behind an explicit abstraction, but you yourself mentioned this already in an earlier mail. i'd call it CONFIGURATION-FIELD-SET? (instead of MAYBE-SET?). it's longer, but we have completion in emacs, and it won't be used a gazillion times all around the code either.

2) the lack of an abstraction for the unset/unspecified value. whatever we use as the marker should be hidden behind either an exported global variable, or a function called UNSET-CONFIGURATION-FIELD! (or something alike). i should have introduced these myself, and then your fix would have been as simple as replacing *UNSPECIFIED* with 'UNSET in the abstraction.

3) the SYMBOL? corner case that your test captures, but it's not a burning issue for me (it doesn't affect the user facing API, once the above leakages are fixed).

do you agree? if yes, will you implement it, or shall i prepare a patch?

one more note: sometimes it's useful to have a field with a maybe type that also has a default, together with the ability to explicitly unset this field.

an example would be a port specification for a torrent client: it has some default port, but it's possible to explicitly unset the port value to request the allocation of a random port at startup.

to better accommodate for this use case, 2) should probably be implemented not as an UNSET-FOO! function, but as a global variable holding the unset value marker. or maybe both?

--
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“There is only one thing more harmful to society than an elected official forgetting the promises he made in order to get elected; that's when he doesn't forget them.”
	— John McCarthy (1927–2011), father of Lisp





  reply	other threads:[~2022-08-11 10:17 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-27 16:23 bug#56799: (gnu services configuration) usage of *unspecified* is problematic Maxim Cournoyer
2022-07-27 16:43 ` Tobias Geerinckx-Rice via Bug reports for GNU Guix
2022-07-27 18:27   ` Attila Lendvai
2022-07-28 15:15     ` Maxim Cournoyer
2022-07-27 18:31   ` Maxim Cournoyer
2022-07-27 18:45     ` Tobias Geerinckx-Rice via Bug reports for GNU Guix
2022-07-27 19:09       ` Maxim Cournoyer
2022-07-27 19:45         ` bug#56799: [PATCH] services: configuration: Step back from *unspecified* Maxim Cournoyer
2022-07-27 19:46         ` bug#56799: (gnu services configuration) usage of *unspecified* is problematic Maxim Cournoyer
2022-07-27 20:20           ` bug#56799: [PATCH v2] gexp: Handle *unspecified* as a gexp input Maxim Cournoyer
2022-07-27 21:43             ` Maxime Devos
2022-07-28 14:58               ` Maxim Cournoyer
2022-07-28  4:41           ` bug#56799: [PATCH v3] " Maxim Cournoyer
2022-08-01  5:08             ` bug#56799: (gnu services configuration) usage of *unspecified* is problematic Maxim Cournoyer
2022-08-01 10:00               ` Maxime Devos
2022-08-01 12:46                 ` Maxim Cournoyer
2022-08-01 13:44             ` Ludovic Courtès
2022-08-01 16:55       ` Maxim Cournoyer
2022-07-28  4:55     ` bokr
2022-07-28 10:26       ` Maxime Devos
2022-07-28 15:09         ` Maxim Cournoyer
2022-08-01 13:49 ` Ludovic Courtès
2022-08-01 15:55   ` Maxim Cournoyer
2022-08-02  7:31     ` Ludovic Courtès
2022-08-02  8:45       ` bokr
2022-08-02 15:06       ` Maxim Cournoyer
2022-08-04 12:19         ` Ludovic Courtès
2022-08-07 22:44           ` Ludovic Courtès
2022-08-08 22:27           ` Attila Lendvai
2022-08-08 23:35             ` Attila Lendvai
2022-08-10  2:17               ` Maxim Cournoyer
2022-08-10  3:26             ` Maxim Cournoyer
2022-08-11 10:15               ` Attila Lendvai [this message]
2022-08-13  6:31                 ` Maxim Cournoyer
2022-08-13 16:47                   ` Attila Lendvai
2022-08-14  2:57                     ` Maxim Cournoyer
2022-08-16 14:00                       ` Attila Lendvai
2022-08-17 13:16                         ` Maxim Cournoyer
2022-08-17 16:00                           ` paren--- via Bug reports for GNU Guix
2022-08-10  0:43           ` Maxim Cournoyer
2022-08-24 12:40 ` bug#56799: [PATCH 1/5] services: configuration: Add a 'maybe-value-set?' procedure Attila Lendvai
2022-08-24 12:40   ` bug#56799: [PATCH 2/5] services: configuration: Add %unset-value exported variable Attila Lendvai
2022-08-24 12:40   ` bug#56799: [PATCH 3/5] services: configuration: Add maybe-value exported procedure Attila Lendvai
2022-08-24 12:40   ` bug#56799: [PATCH 4/5] services: Use the new maybe/unset API Attila Lendvai
2022-08-25  4:18     ` bug#56799: (gnu services configuration) usage of *unspecified* is problematic Maxim Cournoyer
2022-08-24 12:40   ` bug#56799: [PATCH 5/5] services: configuration: Change the value of the unset marker Attila Lendvai
2022-08-25  4:14     ` bug#56799: (gnu services configuration) usage of *unspecified* is problematic Maxim Cournoyer

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://guix.gnu.org/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='sbyTY2P3pKhHq9Rm0XBEy9BqxoAn8jgZzaEI4IZgtAFHZJQ50UJgVFs2ha7iRsGpiZ4Z7c0wyhuvk2_AmgllEIfFAEpizVKU00HEnWirAoQ=@lendvai.name' \
    --to=attila@lendvai.name \
    --cc=56799@debbugs.gnu.org \
    --cc=ludo@gnu.org \
    --cc=maxim.cournoyer@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/guix.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).