Re: Empty headline titles unsupported: Bug?

[Tom Gillespie]

Hi all,
     Here is the 4th (or so) iteration of the grammar for titles that
I think deals with most of the issues in this thread along with a
bunch of nasty test cases. The previous attempts can be inspected in
the git history, but long story short, it is extremely hard to find a
grammar that follows the principle of least surprise and you have to
use the tokenizer to ensure that the tags pattern always parses as
such so that tags don't magically switch to being the title when you
remove the rest of the contents of the title. The final example
L1648-L1665 shows many of the things that should parse as tags and do
with this tokenizer/grammar combination. The key to dealing with the
ambiguity of empty title and tags vs something that looks like tags
but parses as a title (which is surprising) is to use the tokenizer to
greedily recognize tags at the end of the line. This ensures that the
tags pattern at the end of the line always parses as tags and doesn't
switch just because the title is empty. Happy to elaborate. Best,
Tom

https://github.com/tgbugs/laundry/blob/next/laundry/heading.rkt
https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/tokenizer.rkt#L98-L140

https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/test.rkt#L326-L367
https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/test.rkt#L400-L558
https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/test.rkt#L1298-L1369
https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/test.rkt#L1371-L1419
https://github.com/tgbugs/laundry/blob/971cf35683cd60156868c12b070c2dd9e19d8d06/laundry/test.rkt#L1648-L1665