syntax.md and message.abnf can get out of sync

[catamorphism]

I noticed while reviewing #731 that changing the grammar requires changing both spec/syntax.md and spec/message.abnf, since grammar rules appear in both files. This is bound to introduce errors at some point. Instead, a script could be added that extracts the rules from syntax.md and auto-generates message.abnf.

[aphillips]

This has been an annoyance for awhile now. However, if we stabilize the syntax (which will happen in LDML46 because of our stability clause), the frequency of the annoyance should slow down?

I disagree with the idea of auto-generating message.abnf, as that is the source of truth for the syntax.

[catamorphism]

That's fair. I feel like there should be some literate-programming-based way to combine the two documents together and use a tool to view just the grammar rules when desired, but maybe that's overkill.

[aphillips]

IETF RFCs work like that: the ABNF is always embedded into the text and you can pass the RFC into various tools to get the grammar out.

[eemeli]

I agree with @aphillips. Automating this would be more work and more complexity than it's worth.

[aphillips]

I'm closing this item as "won't fix". Reopen if you disagree.