bibtex-enclosing-field is a compiled Lisp function in `bibtex.el'.

(bibtex-enclosing-field &optional COMMA NOERR)

Search for BibTeX field enclosing point.
For `bibtex-mode''s internal algorithms, a field begins at the comma
following the preceding field. Usually, this is not what the user expects.
Thus if COMMA is non-nil, the "current field" includes the terminating comma
as well as the entry delimiter if it appears on the same line.
Unless NOERR is non-nil, signal an error if no enclosing field is found.
On success return bounds, nil otherwise. Do not move point.