[Standards] XEP-0045: Reserved Nicks and GC Compatibility

[Mike Wacker]

Hello,

One of the tenets of XEP-0045 is backwards-compatibility with groupchat 
1.0. I was wondering if reserved nicks break this tenet. XEP-0045 says 
clients SHOULD first try to discover a reserved nick, if any, before 
entering a room. However, the server MAY lock down nicks and return an 
error if the reserved nick is not used. If it does lock down nicks, then 
the client actually MUST (not SHOULD) check for a reserved nick before 
entering the room, since using any other nick would cause an error.

I used the Wayback Machine to look at the old page about the groupchat 
1.0 protocol and early versions of JEP-0045, and none of them indicate 
support for discovering reserved nicks, meaning the client has to set 
the nick instead. Thus, it seems like older clients, including 
groupchat, would actually break if the server locked down nicks and 
returned an error if the reserved nick was not used to enter a room. 
(Though I don't know the history of groupchat other than what old docs 
said, so someone can correct me if there's some missing piece here not 
mentioned in the docs.)

RC7 for XEP-0045 1.25 allows servers to rewrite nicks. If a nick rewrite 
does not break old groupchat clients, perhaps we should say the server 
MUST rewrite the nick instead of returning an error if the nicks are 
locked down and a nick other than the reserved one is used to enter the 
room.

Mike