emacs/show: optionally insert bodies of "deep messages" lazily

This leverages the machinery already there to insert buttons for
attachments.

A potential use-case is browsing the top layers of the tree to decide
which of the lower subtrees to read.

doc/notmuch-emacs.rst

@@ -277,6 +277,9 @@ Display of messages can be controlled by the following variables
 :index:`notmuch-show-header-line`
        |docstring::notmuch-show-header-line|
 
+:index:`notmuch-show-depth-limit`
+       |docstring::notmuch-show-depth-limit|
+
 :index:`notmuch-multipart/alternative-discouraged`
 
    Which mime types to hide by default for multipart messages.

emacs/notmuch-show.el

@@ -110,6 +110,19 @@ displayed."
 		 (function :tag "Function"))
   :group 'notmuch-show)
 
+(defcustom notmuch-show-depth-limit nil
+  "Depth beyond which message bodies are displayed lazily.
+
+If bound to an integer, any message with tree depth greater than
+this will have its body display lazily, initially
+inserting only a button.
+
+If this variable is set to nil (the default) no such lazy
+insertion is done."
+  :type '(choice (const :tag "No limit" nil)
+                 (number :tag "Limit" 10))
+  :group 'notmuch-show)
+
 (defcustom notmuch-show-relative-dates t
   "Display relative dates in the message summary line."
   :type 'boolean
@@ -1030,17 +1043,21 @@ is t, hide the part initially and show the button."
 		    (> notmuch-show-max-text-part-size 0)
 		    (> (length (plist-get part :content))
 		       notmuch-show-max-text-part-size)))
+	 (deep (and notmuch-show-depth-limit
+		    (> depth notmuch-show-depth-limit)))
 	 (beg (point))
 	 ;; This default header-p function omits the part button for
 	 ;; the first (or only) part if this is text/plain.
-	 (button (and (funcall notmuch-show-insert-header-p-function part hide)
+	 (button (and (or deep
+			  (funcall notmuch-show-insert-header-p-function part hide))
 		      (notmuch-show-insert-part-header
 		       nth mime-type
 		       (and content-type (downcase content-type))
 		       (plist-get part :filename))))
-	 ;; Hide the part initially if HIDE is t, or if it is too long
+	 ;; Hide the part initially if HIDE is t, or if it is too long/deep
 	 ;; and we have a button to allow toggling.
 	 (show-part (not (or (equal hide t)
+			     (and deep button)
 			     (and long button))))
 	 (content-beg (point)))
     ;; Store the computed mime-type for later use (e.g. by attachment handlers).

test/T450-emacs-show.sh

@@ -91,6 +91,24 @@ test_emacs '(let ((notmuch-show-only-matching-messages t))
 	(test-visible-output))'
 test_expect_equal_file $EXPECTED/notmuch-show-elide-non-matching-messages-on OUTPUT
 
+test_begin_subtest "Hide bodies of messages by depth"
+test_emacs '(let ((notmuch-show-depth-limit -1))
+	(notmuch-search "thread:{id:87ocn0qh6d.fsf@yoom.home.cworth.org}")
+	(notmuch-test-wait)
+	(notmuch-search-show-thread)
+	(notmuch-test-wait)
+	(test-visible-output))'
+test_expect_equal_file $EXPECTED/notmuch-show-depth OUTPUT
+
+test_begin_subtest "Hide bodies of messages (depth > 1)"
+test_emacs '(let ((notmuch-show-depth-limit 1))
+	(notmuch-search "thread:{id:87ocn0qh6d.fsf@yoom.home.cworth.org}")
+	(notmuch-test-wait)
+	(notmuch-search-show-thread)
+	(notmuch-test-wait)
+	(test-visible-output))'
+test_expect_equal_file $EXPECTED/notmuch-show-depth-1 OUTPUT
+
 test_begin_subtest "notmuch-show: elide non-matching messages (w/ notmuch-show-toggle-elide-non-matching)"
 test_emacs '(let ((notmuch-show-only-matching-messages nil))
 	(notmuch-search "from:lars@seas.harvard.edu and subject:\"Maildir storage\"")

test/emacs-show.expected-output/notmuch-show-depth

@@ -0,0 +1,44 @@
+Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-17) (inbox signed)
+Subject: [notmuch] Working with Maildir storage?
+To: notmuch@notmuchmail.org
+Date: Tue, 17 Nov 2009 14:00:54 -0500
+
+[ multipart/mixed (hidden) ]
+ Mikhail Gusarov <dottedmag@dottedmag.net> (2009-11-17) (inbox signed unread)
+ Subject: Re: [notmuch] Working with Maildir storage?
+ To: notmuch@notmuchmail.org
+ Date: Wed, 18 Nov 2009 01:02:38 +0600
+
+ [ multipart/mixed (hidden) ]
+  Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-17) (inbox signed)
+  Subject: Re: [notmuch] Working with Maildir storage?
+  To: Mikhail Gusarov <dottedmag@dottedmag.net>
+  Cc: notmuch@notmuchmail.org
+  Date: Tue, 17 Nov 2009 15:33:01 -0500
+
+  [ multipart/mixed (hidden) ]
+   Mikhail Gusarov <dottedmag@dottedmag.net> (2009-11-17) (inbox unread)
+   Subject: [notmuch] Working with Maildir storage?
+   To: notmuch@notmuchmail.org
+   Date: Wed, 18 Nov 2009 02:50:48 +0600
+
+   [ text/plain (hidden) ]
+   Keith Packard <keithp@keithp.com> (2009-11-17) (inbox unread)
+   Subject: [notmuch] Working with Maildir storage?
+   To: notmuch@notmuchmail.org
+   Date: Tue, 17 Nov 2009 13:24:13 -0800
+
+   [ text/plain (hidden) ]
+    Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (inbox signed unread)
+    Subject: Re: [notmuch] Working with Maildir storage?
+    To: Keith Packard <keithp@keithp.com>
+    Cc: notmuch@notmuchmail.org
+    Date: Tue, 17 Nov 2009 19:50:40 -0500
+
+    [ multipart/mixed (hidden) ]
+ Carl Worth <cworth@cworth.org> (2009-11-18) (inbox unread)
+ Subject: [notmuch] Working with Maildir storage?
+ To: notmuch@notmuchmail.org
+ Date: Wed, 18 Nov 2009 02:08:10 -0800
+
+ [ text/plain (hidden) ]

test/emacs-show.expected-output/notmuch-show-depth-1

@@ -0,0 +1,119 @@
+Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-17) (inbox signed)
+Subject: [notmuch] Working with Maildir storage?
+To: notmuch@notmuchmail.org
+Date: Tue, 17 Nov 2009 14:00:54 -0500
+
+[ multipart/mixed ]
+[ multipart/signed ]
+[ Unknown key ID 0xD74695063141ACD8 or unsupported algorithm ]
+[ text/plain ]
+I saw the LWN article and decided to take a look at notmuch.  I'm
+currently using mutt and mairix to index and read a collection of
+Maildir mail folders (around 40,000 messages total).
+
+notmuch indexed the messages without complaint, but my attempt at
+searching bombed out. Running, for example:
+
+  notmuch search storage
+
+Resulted in 4604 lines of errors along the lines of:
+
+  Error opening
+  /home/lars/Mail/read-messages.2008/cur/1246413773.24928_27334.hostname,U=3026:2,S:
+  Too many open files
+
+I'm curious if this is expected behavior (i.e., notmuch does not work
+with Maildir) or if something else is going on.
+
+Cheers,
+
+[ 4-line signature. Click/Enter to show. ]
+[ application/pgp-signature ]
+[ text/plain ]
+[ 4-line signature. Click/Enter to show. ]
+ Mikhail Gusarov <dottedmag@dottedmag.net> (2009-11-17) (inbox signed unread)
+ Subject: Re: [notmuch] Working with Maildir storage?
+ To: notmuch@notmuchmail.org
+ Date: Wed, 18 Nov 2009 01:02:38 +0600
+
+ [ multipart/mixed ]
+ [ multipart/signed ]
+ [ Unknown key ID 0x9D20F6503E338888 or unsupported algorithm ]
+ [ text/plain ]
+
+ Twas brillig at 14:00:54 17.11.2009 UTC-05 when lars@seas.harvard.edu did
+ gyre and gimble:
+
+  LK> Resulted in 4604 lines of errors along the lines of:
+
+  LK>   Error opening
+  LK>  
+ /home/lars/Mail/read-messages.2008/cur/1246413773.24928_27334.hostname,U=3026:2,S:
+  LK>   Too many open files
+
+ See the patch just posted here.
+
+ [ 2-line signature. Click/Enter to show. ]
+ [ application/pgp-signature ]
+ [ text/plain ]
+ [ 4-line signature. Click/Enter to show. ]
+  Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-17) (inbox signed)
+  Subject: Re: [notmuch] Working with Maildir storage?
+  To: Mikhail Gusarov <dottedmag@dottedmag.net>
+  Cc: notmuch@notmuchmail.org
+  Date: Tue, 17 Nov 2009 15:33:01 -0500
+
+  [ multipart/mixed (hidden) ]
+   Mikhail Gusarov <dottedmag@dottedmag.net> (2009-11-17) (inbox unread)
+   Subject: [notmuch] Working with Maildir storage?
+   To: notmuch@notmuchmail.org
+   Date: Wed, 18 Nov 2009 02:50:48 +0600
+
+   [ text/plain (hidden) ]
+   Keith Packard <keithp@keithp.com> (2009-11-17) (inbox unread)
+   Subject: [notmuch] Working with Maildir storage?
+   To: notmuch@notmuchmail.org
+   Date: Tue, 17 Nov 2009 13:24:13 -0800
+
+   [ text/plain (hidden) ]
+    Lars Kellogg-Stedman <lars@seas.harvard.edu> (2009-11-18) (inbox signed unread)
+    Subject: Re: [notmuch] Working with Maildir storage?
+    To: Keith Packard <keithp@keithp.com>
+    Cc: notmuch@notmuchmail.org
+    Date: Tue, 17 Nov 2009 19:50:40 -0500
+
+    [ multipart/mixed (hidden) ]
+ Carl Worth <cworth@cworth.org> (2009-11-18) (inbox unread)
+ Subject: [notmuch] Working with Maildir storage?
+ To: notmuch@notmuchmail.org
+ Date: Wed, 18 Nov 2009 02:08:10 -0800
+
+ On Tue, 17 Nov 2009 14:00:54 -0500, Lars Kellogg-Stedman <lars at
+ seas.harvard.edu> wrote:
+ > I saw the LWN article and decided to take a look at notmuch.  I'm
+ > currently using mutt and mairix to index and read a collection of
+ > Maildir mail folders (around 40,000 messages total).
+
+ Welcome, Lars!
+
+ I hadn't even seen that Keith's blog post had been picked up by lwn.net.
+ That's very interesting. So, thanks for coming and trying out notmuch.
+
+ >   Error opening
+ > /home/lars/Mail/read-messages.2008/cur/1246413773.24928_27334.hostname,U=3026:2,S:
+ >   Too many open files
+
+ Sadly, the lwn article coincided with me having just introduced this
+ bug, and then getting on a Trans-Atlantic flight. So I fixed the bug
+ fairly quickly, but there was quite a bit of latency before I could push
+ the fix out. It should be fixed now.
+
+ > I'm curious if this is expected behavior (i.e., notmuch does not work
+ > with Maildir) or if something else is going on.
+
+ Notmuch works just fine with maildir---it's one of the things that it
+ likes the best.
+
+ Happy hacking,
+
+ -Carl