Room version grammar is inconsistent

[turt2live]

Link to problem area: https://spec.matrix.org/v1.5/rooms/#room-version-grammar

Issue

Room versions MUST NOT be empty and SHOULD contain only the characters a-z, 0-9, ., and -.

but then we go on to describe a grammar which doesn't honour the "SHOULD": is it legal to put emoji (for example) in room versions or not?

[richvdh]

is it legal to put emoji (for example) in room versions or not?

what? no! why would it be?

[turt2live]

"SHOULD" implies the grammar is at most a suggestion.

[richvdh]

for links, afaict this wording was introduced by matrix-org/matrix-spec-proposals#1773

[turt2live]

ftr, this appears to have actually come from matrix-org/matrix-spec-proposals#1516 which links off to the MSC's google doc: https://docs.google.com/document/d/1urKgReoHqxX8R_XtySB17dPi-DZcKhqTEL2_s895Wz0/edit

That doc says:

It is recommended that version strings are limited to the characters a-z, 0-9, . and -.

At the time, the MSC process was still very new and being figured out, so I can believe it was a misunderstanding that "It is recommended" was treated as a SHOULD instead of a recommendation to the SCT. Ie: it could feasibly be reworded to say "It is recommended that [the Spec Core Team consider] version strings be limited to...".