bug#45770: 28.0.50; `gnus-search-run-search' for imap does not take parentheses into account

[Michael Welsh Duggan]

When using the `gnus-search-imap' backend for `gnus-search', there is a
bug in the `gnus-search-run-search' method.  When the search query
begins with parentheses (such as "(OR FROM A FROM B)"), the naive check
for a known IMAP keyword at the beginning fails due to the parenthesis,
and gnus-search adds "TEXT " to the beginning of the query.

Moreover, these are several search keys that are not in
`gnus-search-imap-search-keys'.  These are "new", "not", "old", and
"or".

I include a minimal patch for these problems.

There's another misfeature which I have not attempted to fix that made
debugging the problem much more difficult.  If the result of a query is
not OK, this fact just gets ignored by `gnus-search-run-search' and the
search group is considered empty.  Even after fixing the above problems,
this is a problem when doing a raw search, as one doesn't know whether
the query is bad or if it just does not result in any messages.

Example:

C-u G G "((OR" RET

This results in something like:

577841 BAD Error in IMAP command UID SEARCH: Missing ')' (0.001 + 0.000 secs).

in the process buffer.

Here's a small patch for the first two issues:

diff --git a/lisp/gnus/gnus-search.el b/lisp/gnus/gnus-search.el
index 44f43b073c..f20f9586d2 100644
--- a/lisp/gnus/gnus-search.el
+++ b/lisp/gnus/gnus-search.el
@@ -1036,7 +1036,7 @@ gnus-search-imap-search-keys
   '(body cc bcc from header keyword larger smaller subject text to uid x-gm-raw
         answered before deleted draft flagged on since recent seen sentbefore
         senton sentsince unanswered undeleted undraft unflagged unkeyword
-        unseen all)
+         unseen all new not old or)
   "Known IMAP search keys.")
 
 ;; imap interface
@@ -1072,9 +1072,9 @@ gnus-search-imap-search-keys
       ;; A bit of backward-compatibility slash convenience: if the
       ;; query string doesn't start with any known IMAP search
       ;; keyword, assume it is a "TEXT" search.
-      (unless (and (string-match "\\`[^[:blank:]]+" q-string)
+      (unless (and (string-match "\\`(*\\([^[:blank:]]+\\)" q-string)
                   (memql (intern-soft (downcase
-                                       (match-string 0 q-string)))
+                                        (match-string 1 q-string)))
                          gnus-search-imap-search-keys))
        (setq q-string (concat "TEXT " q-string)))

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 
1.16.0)
 of 2020-12-20 built on maru2
Repository revision: 27347db0069f9d9fd0152274bfc7c649c387f185
Repository branch: md5i
Windowing system distributor 'The X.Org Foundation', version 11.0.12009000
System Description: Debian GNU/Linux bullseye/sid

Configured using:
 'configure --with-modules --without-toolkit-scroll-bars
 --with-x-toolkit=lucid --with-wide-int --with-gameuser=:staff
 'CFLAGS=-Og -ggdb3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB LUCID X11 XDBE XIM MODULES THREADS LIBSYSTEMD JSON PDUMPER LCMS2

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Group

Minor modes in effect:
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  line-number-mode: t

Load-path shadows:
/home/md5i/.emacs.d/elpa/cmake-mode-20201217.1410/cmake-mode hides 
/usr/share/emacs/site-lisp/cmake-mode

Features:
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Memory information:
((conses 16 3100306 317740)
 (symbols 48 59489 65)
 (strings 32 300970 101472)
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 (vectors 16 156616)
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 (buffers 984 241))

-- 
Michael Welsh Duggan
(md5i@md5i.com)