Re: Org-syntax: Intra-word markup

[Tom Gillespie]

> Since org is a valid export backend though, perhaps this behaviour should be
> reserved for @@:…@@, i.e. no export backend, which I think semantically fits
> fairly nicely.

This ends up being even more convenient than I initially realized.
The current spec for export snippets is ambiguous when it says
"NAME can contain any alpha-numeric character and hyphens"
but the implementation behavior requires that "any" means "at
least one" and is implemented using the + regex operator.

What this means is that @@:...@@ syntax is not actually used
in Org at all at the moment and renders as plain text. I agree that
we need to avoid @@org:..@@ because it has legitimate uses.
Making a back-end of empty string valid for parse separately
syntax thus makes @@ syntax more regular overall, and allows
@@:...@@ to be processed separately because it currently
never enters the export snippet processing.

This is important because export snippets do not seem to be easily
accessible to earlier phases of the org-export machinery, i.e. there
isn't a nice centralized place to preprocess @@org:...@@ even
if we wanted to. On the other hand @@:...@@ isn't processed
at all. I could be missing something in the org export code though.

It will take a bit of work to get this behavior implemented I think,
but it doesn't seem to have any conflicts. Some users may have
set the empty backend to expand manually via
org-export-snippet-translation-alist, but as long as we give
org-export-snippet-translation-alist priority and warn people
that setting "" manually will disable the new functionality
then there shouldn't be any disruption. The behavior also sort
of matches what we would want the empty string to be in this
case, which is "all backends" and of course the only markup
that makes sense for "all backends" is org itself!

Best,
Tom