[PATCH 2/2] emacs: Prefer Content-Description over filename for part buttons

["W. Trevor King" <wking@tremily.us>]

On the rss2email list, Victor Orlikowski pointed out [1] that a number
of MUAs don't use the Subject header of attached message/rfc822 parts
to label multipart/digest subparts [2].  Instead, notmuch and several
other MUAs use the filename parameter [3] as a content hint.  Using
the filename parameter seems more sane than diving into the
message/rfc822 part header, but that's still not what the filename
parameter was designed for.  It makes more sense to me to use the
message/rfc822 part's Content-Description header (which I just taught
notmuch-show to export), falling back on the filename parameter if
Content-Description isn't set.

[1]: http://article.gmane.org/gmane.mail.rss2email/211
[2]: Digests: http://tools.ietf.org/html/rfc2046#section-5.1.5
[3]: Filename: http://tools.ietf.org/search/rfc2183#section-2.3
---
 NEWS                                               |  7 ++
 emacs/notmuch-show.el                              |  4 +-
 test/T450-emacs-show.sh                            | 12 ++++
 test/corpus/cur/24:2,                              |  1 +
 .../notmuch-show-buttons-content-description       | 84 ++++++++++++++++++++++
 .../notmuch-show-buttons-filename                  | 74 +++++++++++++++++++
 6 files changed, 181 insertions(+), 1 deletion(-)
 create mode 100644 test/emacs-show.expected-output/notmuch-show-buttons-content-description
 create mode 100644 test/emacs-show.expected-output/notmuch-show-buttons-filename

diff --git a/NEWS b/NEWS
index 0f7b1c8..2154872 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,13 @@ Command-Line Interface
 
 `notmuch show` now includes envelope Content-Description headers.
 
+Emacs Interface
+---------------
+
+`notmuch-show` mode prefers Content-Description to filename when
+naming part buttons.  This is useful for finding interesting parts of
+multipart/digest messages, assuming the digest-creator set that field.
+
 Notmuch 0.17 (2013-12-30)
 =========================
 
diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 1ac80ca..dbff3a8 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -874,13 +874,15 @@ useful for quoting in replies)."
 			content-type))
 	 (nth (plist-get part :id))
 	 (beg (point))
+	 (name (or (plist-get part :content-description)
+		   (plist-get part :filename)))
 	 ;; Hide the part initially if HIDE is t.
 	 (show-part (not (equal hide t)))
 	 ;; We omit the part button for the first (or only) part if
 	 ;; this is text/plain, or HIDE is 'no-buttons.
 	 (button (unless (or (equal hide 'no-buttons)
 			     (and (string= mime-type "text/plain") (<= nth 1)))
-		   (notmuch-show-insert-part-header nth mime-type content-type (plist-get part :filename))))
+		   (notmuch-show-insert-part-header nth mime-type content-type name)))
 	 (content-beg (point)))
 
     ;; Store the computed mime-type for later use (e.g. by attachment handlers).
diff --git a/test/T450-emacs-show.sh b/test/T450-emacs-show.sh
index 2a3a535..5650f04 100755
--- a/test/T450-emacs-show.sh
+++ b/test/T450-emacs-show.sh
@@ -106,6 +106,18 @@ test_emacs '(notmuch-search "from:lars@seas.harvard.edu and subject:\"Maildir st
 	(test-visible-output)'
 test_expect_equal_file OUTPUT $EXPECTED/notmuch-show-indent-thread-content-off
 
+test_begin_subtest "buttons prefer Content-Description"
+test_emacs '(let ((notmuch-crypto-process-mime nil))
+	(notmuch-show "id:20091118010116.GC25380@dottiness.seas.harvard.edu")
+	(test-visible-output))'
+test_expect_equal_file OUTPUT $EXPECTED/notmuch-show-buttons-content-description
+
+test_begin_subtest "buttons fallback to filename"
+test_emacs '(let ((notmuch-crypto-process-mime nil))
+	(notmuch-show "id:20091118005829.GB25380@dottiness.seas.harvard.edu")
+	(test-visible-output))'
+test_expect_equal_file OUTPUT $EXPECTED/notmuch-show-buttons-filename
+
 test_begin_subtest "id buttonization"
 add_message '[body]="
 id:abc
diff --git a/test/corpus/cur/24:2, b/test/corpus/cur/24:2,
index c800020..f9418d2 100644
--- a/test/corpus/cur/24:2,
+++ b/test/corpus/cur/24:2,
@@ -104,6 +104,7 @@ Harvard University School of Engineering and Applied Sciences
 
 --KdquIMZPjGJQvRdI
 Content-Type: text/plain; charset=us-ascii
+Content-Description: v2 of the selectable usage() stream patch
 Content-Disposition: attachment; filename="notmuch-help.patch"
 Content-Transfer-Encoding: quoted-printable
 
diff --git a/test/emacs-show.expected-output/notmuch-show-buttons-content-description b/test/emacs-show.expected-output/notmuch-show-buttons-content-description
new file mode 100644
index 0000000..622c94e
--- /dev/null
+++ b/test/emacs-show.expected-output/notmuch-show-buttons-content-description
@@ -0,0 +1,84 @@
+Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (attachment inbox signed unread)
+Subject: [notmuch] "notmuch help" outputs to stderr?
+ Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (attachment inbox signed)
+ Subject: Re: [notmuch] "notmuch help" outputs to stderr?
+ To: notmuch <notmuch@notmuchmail.org>
+ Date: Tue, 17 Nov 2009 20:01:16 -0500
+
+ [ multipart/mixed ]
+ [ multipart/signed ]
+ [ multipart/mixed ]
+ [ text/plain ]
+ > I've attached a patch that lets usage() take a FILE * argument so that
+ > you can output to stderr in response to usage errors, and stdout in
+ > response to an explicit request.
+
+ Whoops, missed a couple of stderr's in that last patch.  New one
+ attached.
+
+ [ 4-line signature. Click/Enter to show. ]
+ [ v2 of the selectable usage() stream patch: text/plain ]
+ diff --git a/notmuch.c b/notmuch.c
+ index c47e640..446c810 100644
+ --- a/notmuch.c
+ +++ b/notmuch.c
+ @@ -157,23 +157,23 @@ command_t commands[] = {
+  };
+
+  static void
+ -usage (void)
+ +usage (FILE *out)
+  {
+      command_t *command;
+      unsigned int i;
+
+ -    fprintf (stderr, "Usage: notmuch <command> [args...]\n");
+ -    fprintf (stderr, "\n");
+ -    fprintf (stderr, "Where <command> and [args...] are as follows:\n");
+ -    fprintf (stderr, "\n");
+ +    fprintf (out, "Usage: notmuch <command> [args...]\n");
+ +    fprintf (out, "\n");
+ +    fprintf (out, "Where <command> and [args...] are as follows:\n");
+ +    fprintf (out, "\n");
+
+      for (i = 0; i < ARRAY_SIZE (commands); i++) {
+	 command = &commands[i];
+
+ -	fprintf (stderr, "\t%s\t%s\n\n", command->name, command->summary);
+ +	fprintf (out, "\t%s\t%s\n\n", command->name, command->summary);
+      }
+
+ -    fprintf (stderr, "Use \"notmuch help <command>\" for more details on
+ each command.\n\n");
+ +    fprintf (out, "Use \"notmuch help <command>\" for more details on each
+ command.\n\n");
+  }
+
+  static int
+ @@ -183,8 +183,8 @@ notmuch_help_command (unused (void *ctx), int argc, char
+ *argv[])
+      unsigned int i;
+
+      if (argc == 0) {
+ -	fprintf (stderr, "The notmuch mail system.\n\n");
+ -	usage ();
+ +	fprintf (stdout, "The notmuch mail system.\n\n");
+ +	usage (stdout);
+	 return 0;
+      }
+
+ @@ -192,8 +192,8 @@ notmuch_help_command (unused (void *ctx), int argc, char
+ *argv[])
+	 command = &commands[i];
+
+	 if (strcmp (argv[0], command->name) == 0) {
+ -	    fprintf (stderr, "Help for \"notmuch %s\":\n\n", argv[0]);
+ -	    fprintf (stderr, "\t%s\t%s\n\n%s\n\n", command->name,
+ +	    fprintf (stdout, "Help for \"notmuch %s\":\n\n", argv[0]);
+ +	    fprintf (stdout, "\t%s\t%s\n\n%s\n\n", command->name,
+		      command->summary, command->documentation);
+	     return 0;
+	 }
+ [ application/pgp-signature ]
+ [ text/plain ]
+ [ 4-line signature. Click/Enter to show. ]
diff --git a/test/emacs-show.expected-output/notmuch-show-buttons-filename b/test/emacs-show.expected-output/notmuch-show-buttons-filename
new file mode 100644
index 0000000..8fb4d89
--- /dev/null
+++ b/test/emacs-show.expected-output/notmuch-show-buttons-filename
@@ -0,0 +1,74 @@
+Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (attachment inbox signed)
+Subject: [notmuch] "notmuch help" outputs to stderr?
+To: notmuch <notmuch@notmuchmail.org>
+Date: Tue, 17 Nov 2009 19:58:29 -0500
+
+[ multipart/mixed ]
+[ multipart/signed ]
+[ multipart/mixed ]
+[ text/plain ]
+I'm just noticing that 'notmuch help ...' outputs to stderr, which
+isn't terribly intuitive.  For example, the obvious invocation:
+
+  notmuch help | less
+
+...isn't terribly helpful.
+
+I've attached a patch that lets usage() take a FILE * argument so that
+you can output to stderr in response to usage errors, and stdout in
+response to an explicit request.
+
+[ 4-line signature. Click/Enter to show. ]
+[ notmuch-help.patch: text/plain ]
+diff --git a/notmuch.c b/notmuch.c
+index c47e640..a35cb99 100644
+--- a/notmuch.c
++++ b/notmuch.c
+@@ -157,23 +157,23 @@ command_t commands[] = {
+ };
+
+ static void
+-usage (void)
++usage (FILE *out)
+ {
+     command_t *command;
+     unsigned int i;
+
+-    fprintf (stderr, "Usage: notmuch <command> [args...]\n");
+-    fprintf (stderr, "\n");
+-    fprintf (stderr, "Where <command> and [args...] are as follows:\n");
+-    fprintf (stderr, "\n");
++    fprintf (out, "Usage: notmuch <command> [args...]\n");
++    fprintf (out, "\n");
++    fprintf (out, "Where <command> and [args...] are as follows:\n");
++    fprintf (out, "\n");
+
+     for (i = 0; i < ARRAY_SIZE (commands); i++) {
+	command = &commands[i];
+
+-	fprintf (stderr, "\t%s\t%s\n\n", command->name, command->summary);
++	fprintf (out, "\t%s\t%s\n\n", command->name, command->summary);
+     }
+
+-    fprintf (stderr, "Use \"notmuch help <command>\" for more details on each
+command.\n\n");
++    fprintf (out, "Use \"notmuch help <command>\" for more details on each
+command.\n\n");
+ }
+
+ static int
+@@ -183,8 +183,8 @@ notmuch_help_command (unused (void *ctx), int argc, char
+*argv[])
+     unsigned int i;
+
+     if (argc == 0) {
+-	fprintf (stderr, "The notmuch mail system.\n\n");
+-	usage ();
++	fprintf (stdout, "The notmuch mail system.\n\n");
++	usage (stdout);
+	return 0;
+     }
+[ application/pgp-signature ]
+[ text/plain ]
+[ 4-line signature. Click/Enter to show. ]
+ Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (attachment inbox signed)
-- 
1.8.5.2.8.g0f6c0d1