Re: nnml splitting on encoded headers

[Simon Josefsson <jas@extundo.com>]

Russ Allbery <rra@stanford.edu> writes:

>> and this snippet of code from nnmail-article-group:
>
>>     	;; Decode MIME headers and charsets.
>>     	(let ((mail-parse-charset nnmail-mail-splitting-charset))
>>     	  (mail-decode-encoded-word-region (point-min) (point-max)))
>
> Um, that's an extremely serious bug for me.  That means I can't upgrade to
> any newer version of Gnus unless there's some way to turn this off, as far
> and away the most successful spam filtering rules that I have are those
> that catch irregularities of the original, encoded or untagged 8-bit
> Subject line.
>
> Telling Gnus to re-encode before split rules apply won't cut it, I
> believe, unless that re-encoding leaves raw 8-bit that was originally in
> the Subject header alone.
>
> So... how do I turn this feature off?  I can understand how this would be
> useful for people who can read other character sets, so I don't want to
> see it removed entirely, but it's a serious problem for me.

This patch should make the behaviour customizable.  Does it work?  One
could argue about what the default should be, but Lars made it the
default so I won't change it.

Hm. Perhaps the default really should be off since comparing non-ascii
strings in emacs does not work by default.  The same character in
Latin-1, Latin-9 or Unicode is not regarded as the same by Emacs, so
comparing decoded values doesn't work.  It is also more backwards
compatible.  Opinions?

--- nnmail.el.~6.41.~	Thu May 16 16:51:44 2002
+++ nnmail.el	Mon Jun  3 19:42:26 2002
@@ -484,6 +484,11 @@
   :group 'nnmail
   :type 'symbol)
 
+(defcustom nnmail-mail-splitting-decodes t
+  "Whether the nnmail splitting functionality should MIME decode headers."
+  :group 'nnmail
+  :type 'boolean)
+
 ;;; Internal variables.
 
 (defvar nnmail-article-buffer " *nnmail incoming*"
@@ -1000,8 +1005,9 @@
 	;; Copy the headers into the work buffer.
 	(insert-buffer-substring obuf beg end)
 	;; Decode MIME headers and charsets.
+	(when nnmail-mail-splitting-decodes
 	(let ((mail-parse-charset nnmail-mail-splitting-charset))
-	  (mail-decode-encoded-word-region (point-min) (point-max)))
+	    (mail-decode-encoded-word-region (point-min) (point-max))))
 	;; Fold continuation lines.
 	(goto-char (point-min))
 	(while (re-search-forward "\\(\r?\n[ \t]+\\)+" nil t)
--- gnus.texi.~6.281.~	Thu May 23 21:22:49 2002
+++ gnus.texi	Mon Jun  3 19:50:36 2002
@@ -12439,6 +12439,15 @@
 @code{nnmail-split-header-length-limit} are excluded from the split
 function.
 
+@vindex nnmail-mail-splitting-charset
+@vindex nnmail-mail-splitting-decodes
+By default the splitting codes MIME decodes headers so you can match
+on non-ASCII strings.  The @code{nnmail-mail-splitting-charset}
+variable specifies the default charset for decoding.  The behaviour
+can be turned off completely by binding
+@code{nnmail-mail-splitting-decodes} to nil, which is useful if you
+want to match articles based on the raw header data.
+
 Gnus gives you all the opportunity you could possibly want for shooting
 yourself in the foot.  Let's say you create a group that will contain
 all the mail you get from your boss.  And then you accidentally