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Ignore missing disco#info feature in disco#info responses

Jonas Schäfer requested to merge jssfr/xmpp-rs:feature/ignore-missing-disco-info into main

xmpp-rs normally has the stance to get buggy implementations fixed rather than dropping checks. In this particular case I think this is not a good use of resources:

  • The disco#info feature var conveys no actual information: If an implementation replies properly to a disco#info query, it is already implied that it supports the protocol.

  • There are broken server implementations out there. A lot of them (all recent (>= 0.10 && < 0.13 AFAICT) Prosody IM instances). At this point in time, xmpp-rs is unable to query disco#info from MUCs hosted on such prosody versions, except by workarounds (such as the one removed in this diff).

The case would be different if there were no (deployed) implementations which had this bug or if the bug actually had an effect on clients. Especially the latter is not the case though, as pointed out above.

Hence, I conclude that this check is overly pedantic, and while it is true to the letter of XEP-0030, the resources (time, emotional energy of dealing with bugs, punching patches through to stable distributions, etc. etc.) spent on getting this fixed would be better invested elsewhere.

In addition, the workaround is extremely ugly and, even in the xmpp-rs implementation, has no test coverage. Without test coverage of such an implementation, it is bound to break in funny ways when xmpp-rs changes the strings of its error messages (which is something one might do even outside a breaking release).

Edited by Jonas Schäfer

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