From a UI perspective this looks similar to what was already provided
for from, subject, and mid, but the implementation is quite
different. It uses the database's list of terms to construct a term
based query equivalent to the passed regular expression.
The non-field processor behaviour is is convert the corresponding
queries into a search for the unprefixed terms. This yields pretty
surprising results so I decided to generate a query that would match
the terms (i.e. none with that prefix) generated for an empty header.
The argument is that if the string passed to the field processor has
no spaces, then the added quotes won't have any benefit except for
disabling wildcards. But disabling wildcards doesn't seem very useful
in the normal Xapian query parser, since they're stripped before
generating terms anyway. It does mean that the query 'from:"foo*"' will
not be precisely equivalent to 'from:foo' as it is for the non
field-processor version.
This was broken by the addition of regexp searching. The detection of
wildcards is not currently done in the recursive call to parse_query,
because of quoting issues.
The main goal is to prepare the way for non-destructive (or at least
less destructive) exclude tag handling. It does this by having a
pre-parsed query available for further processing. This also allows us
to provide slightly more precise error messages.
the idea is that you can run
% notmuch search subject:/<your-favourite-regexp>/
% notmuch search from:/<your-favourite-regexp>/
or
% notmuch search subject:"your usual phrase search"
% notmuch search from:"usual phrase search"
This feature is only available with recent Xapian, specifically
support for field processors is needed.
It should work with bindings, since it extends the query parser.
This is easy to extend for other value slots, but currently the only
value slots are date, message_id, from, subject, and last_mod. Date is
already searchable; message_id is left for a followup commit.
This was originally written by Austin Clements, and ported to Xapian
field processors (from Austin's custom query parser) by yours truly.
