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
next prev parent 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
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