Dear community,

it's been a while I spoke up here.

I would like to discuss the removal of the following part-sentence from 
XEP-0030 (in Final status!):

> every entity MUST support at least the 
> 'http://jabber.org/protocol/disco#info' feature

Announcing that feature is redundant: An entity which replies with a properly 
constructed `<query xmlns="http://jabber.org/protocol/disco#info"/>` element 
is bound to (and has always been bound to) have implemented XEP-0030 to the 
best of its knowledge.

As this is a Final(!) status XEP, here is my estimate of the impact this 
change has:

- Implementations which required the presence of this feature on the 
  receiving side would now become non-compliant: They might assume
  that the remote entity did not really support XEP-0030 and fail with
  an error.

  Such implementations would need to be adapted in order to be able to
  interoperate with implementations which follow a revised version of
  XEP-0030.

I don't see any other impact. I also strongly suspect that the set of 
implementations which follow XEP-0030 to the letter is rather slim (I only 
know of a single one, which would be the Rust XMPP library xmpp-rs [1]).

The reason why this came up: There have in the past been cases ([2] and 
another, not-yet-filed issue against Prosody IM where the disco#info feature 
is missing from MUCs) where implementations didn't emit this feature. The 
seeming pointlessness and lack of information conveyed by this feature var 
make it easy to overlook and low-priority to fix. The fact that this has gone 
undiscovered for at least one Prosody IM release cycle further supports the 
assumption that the number of implementations which rely on that part of the 
spec is rather small.

Your input is welcome.

kind regards,
Jonas Schäfer
(these days without "special" role in the standards process)

   [1]: And there exists at least one fork which removed that check:
        https://gitlab.com/nesium/xmpp-rs/-/commit/1ddb050
   [2]: https://issues.prosody.im/1664

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