Bug#704527: biber: Character "(" not allowed in key although valid in BiBTeX

[Mark J. Nelson]

This bug should perhaps be reassigned to libbtparse1, since biber 
currently defers to btparse on this matter. Unless biber would consider 
changing its parsing back-end, it should probably be fixed (if at all) 
in btparse.

 From the btparse syntax documentation at 
http://search.cpan.org/~gward/btparse-0.34/doc/bt_language.pod, 
parentheses are purposely excluded from keys, but it's not clear if 
that's due to a misunderstanding about whether they were allowed in 
BibTeX. The documentation justifies why btparse removes '@', '\', and 
'~' from the characters allowed in keys, even though BibTeX accepts 
those three chars. But the docs claim that the following 10 characters 
were already disallowed in BibTeX keys:
" # % ' ( ) , = { }

As you point out, this seems not to be true, since parentheses do work 
in BibTeX. From my (non-expert) read of the PCCTS grammar under the 
hood, it *should* be an easy fix: LPAREN as a semantically meaningful 
element is only used in one very specific place in a BibTeX grammar, in 
@comments, which shouldn't interfere with permitting parentheses in 
entry keys. But I have not tried it.

Best,
Mark

-- 
Mark J. Nelson
IT University of Copenhagen
http://www.kmjn.org/