casemapping: support rfc1459/rfc1459-strict

[ghost]

This was discussed some in IRC, but it would be nice if ergo supported rfc1459 and rfc1459-strict casemapping as well.

Docs: Horse Docs

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Notes: InspIRCd and UnrealIRCd both seem to also default to ascii like ergo. (based on GitHub code search)

Libera (the largest IRC network) uses rfc1459. I imagine most of the top 10 do.

chatlogs

``` 20:31:41 Yes, but my question is really: can ergo support rfc1459 (and rfc1459-strict) and should one of those be the default? 20:32:07 <@slingamn> i think my answers would be "potentially, but why would we want to?" and "no" 20:32:29 <@slingamn> the behavior we implement is a de facto standard and we publish an 005 token describing it 20:32:38 to match what users expect if other IRC networks already do so, mostly 20:33:04 Can say one of my users was very shocked to see someone could take {their_nick} when they had [their_nick] already. :P 20:34:07 <@slingamn> hmm 20:34:59 I'm checking InspIRCd and UnrealIRCd which dwarf ergo by raw server count. I know Libera uses rfc1459. 20:35:58 (And Freenode before it) 20:36:01 <@slingamn> i think it's not a clear user expectation at this point 20:36:09 <@slingamn> you can open an issue...i think dan might have thoughts 20:37:10 looks like InspIRCd and UnrealIRCd both also default to ascii 20:37:37 But I'll have to check the top 10 now :P https://netsplit.de/networks/top10.php 20:37:38 -@ErgoBot- IRC Networks - Top 10 in the annual comparison 20:38:29 <@slingamn> i would guess that most large networks use rfc1459 20:38:45 <@slingamn> but i would also guess that the distinction is important to very few people 20:39:10 <@dan> I’d rather default to ascii, easier for new client authors to implement imo and more appropriate for newer networks, but ye smol distinction 20:39:27 <@slingamn> ohai dan 20:39:33 <@dan> haihai 20:40:25 <@slingamn> dan: we could open a ticket to support rfc1459 and/or rfc1459-strict, and make it incompatible with PRECIS (if you have PRECIS enabled then you must use CASEMAPPING=ascii) 20:40:37 <@slingamn> but, i don't think it's much of a priority 20:40:49 * xnaas can definitely open an issue and you can comment "PRs welcome" 😉 20:40:55 * xnaas knows how FOSS works 20:40:57 😉 20:41:02 <@slingamn> it would also create some terminological confusion because the config key that controls utf8mapping is named 'casemapping', lol 20:41:11 <@dan> if you’d like to maintain it then totally open to having it ;D 20:41:16 <@dan> ehe ```

[slingamn]

This would be a fun thing to do, in keeping with our overall "reference implementation" mandate, and pretty easy. We'd basically just need to add them here:

https://github.com/ergochat/ergo/blob/c67835ce5c5547df36476adfe18850ff75f4c332/irc/strings.go#L49-L63

and then add corresponding cases to casefoldWithSetting and skeleton (precis and permissive would use the real skeletonization, ascii and the two new options would use the identity function).

[slingamn]

Oh, and the 005 token would have to be made conditional:

https://github.com/ergochat/ergo/blob/c67835ce5c5547df36476adfe18850ff75f4c332/irc/config.go#L1625