[Patch v4] lib: regexp matching in 'subject' and 'from'

[David Bremner]

Tomi Ollila <tomi.ollila at iki.fi> writes:

>
> Why would not mesasge_id not be useful to regex match. I can come up quite
> a few use cases... but if there are techinal difficulties... then that
> should be mentioned instead.

I'll have a look. Since the first version of this patch (when that
message was written), people have actually asked for some kind of
wildcard matching of message-ids.

>
> maybe this commit message should inform that xapian with field processors
> (1.4.x) is required for this feature -- and emphasize it a bit better in
> manual page ?
>
> Probably '//' is used to escape '/' -- should such a character ever needed
> in regex search.
>

Currently no escaping is needed because it only looks at the first and
last characters of the string (the usual xapian/shell rules mean that "" might
be needed).

The following seem to work as hoped

# match a / with a space before it

% notmuch search 'subject:"/ //"'

# just a slash

% notmuch search subject:///

# anchored slash

% notmuch search subject:/^//

The trailing slash is actually decorative, we could drop it. Actually
*blush* I just noticed the current code is missing something from this line

         if (str.at (0) == '/' && str.at (str.size () - 1)){

_if_ that line is fixed, then it will have the slightly odd behaviour of

subject:/blah

doing a non-regex search

We could also throw an error for that case, maybe that's the best option.