Re: patch to add new link type "infoi" that leverages Info-index command

[emacs18@gmail.com (Richard Y. Kim)]

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Hi Nicolas,

Thanks for your feedback.  Attached is new patch which incorporates all
your suggestions except the following:

> Not directly related to your patch, but shouldn't it be
>
>   (user-error "Could not open: %s" name)

I'm not sure what you mean by this.  Do you mean that the verb "open" is
more approrpriate than "find" in the error message, i.e., "Could not
open" rather than "Could not find"?  If so, then it seems like "find" is
more appropriate since "open" seems like there was a problem with
opening a file when the problem is that a particular node was not found
after successfully opening a file.  Please let me know if I
misunderstood.  Thanks again for your valuable feedbacks.


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From 16c25b88043f6f84c6d3df14ca3018040a09fe25 Mon Sep 17 00:00:00 2001
From: Kim <emacs18@gmail.com>
Date: Sat, 15 Nov 2014 10:37:39 -0800
Subject: [PATCH] org-info: try info index if info node is not found

* lisp/org-info.el (org-info-follow-link): Attempt index lookup if node
  lookup fails.

* doc/org.texi (External links): Update info links.

Info index is almost always finer grain than info nodes.  For example
with this change, [[info:libc#close]] brings up not only
"(libc)Opening and Closing Files" info node, but also place the cursor
on the line that documents "close" function within the node.  This is
done by looking up "close"in the index upon failing to find a node
named "close".  Hence one can now link function, variable and other
names that are in the index rather than being limited to info node
names.  Typically there are far more index items than there are node
names.  For example libc manual has about 700 nodes, but over 4000
concept, type, function, and variables index items.  More examples of
new ways to create links are shown using org.info as example

- [[info:org#org-clock-idle-time]] uses "Variable Index"
- [[info:org#org-capture]] uses "Command and Function Index".
- [[info:org#timestamp]] uses "Main Index"
- [[info:org#C-c C-c]] uses "Key Index"

TINYCHANGE
---
 doc/org.texi     |  2 +-
 lisp/org-info.el | 15 +++++++++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/doc/org.texi b/doc/org.texi
index b01db2c..fcaee0c 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -3575,7 +3575,7 @@ gnus:group                                @r{Gnus group link}
 gnus:group#id                             @r{Gnus article link}
 bbdb:R.*Stallman                          @r{BBDB link (with regexp)}
 irc:/irc.com/#emacs/bob                   @r{IRC link}
-info:org#External links                   @r{Info node link}
+info:org#External links                   @r{Info node or index link}
 shell:ls *.org                            @r{A shell command}
 elisp:org-agenda                          @r{Interactive Elisp command}
 elisp:(find-file-other-frame "Elisp.org") @r{Elisp form to evaluate}
diff --git a/lisp/org-info.el b/lisp/org-info.el
index 8a2d717..7c828a6 100644
--- a/lisp/org-info.el
+++ b/lisp/org-info.el
@@ -67,11 +67,18 @@
   "Follow an Info file and node link specified by NAME."
   (if (or (string-match "\\(.*\\)[#:]:?\\(.*\\)" name)
           (string-match "\\(.*\\)" name))
-      (progn
+      (let ((filename (match-string 1 name))
+	    (nodename-or-index (or (match-string 2 name) "Top")))
 	(require 'info)
-        (if (match-string 2 name) ; If there isn't a node, choose "Top"
-            (Info-find-node (match-string 1 name) (match-string 2 name))
-          (Info-find-node (match-string 1 name) "Top")))
+	;; If nodename-or-index is invalid node name, then look it
+	;; up in the index.
+	(condition-case nil
+	    (Info-find-node filename nodename-or-index)
+	  (user-error (Info-find-node filename "Top")
+		      (condition-case nil
+			  (Info-index nodename-or-index)
+			(user-error (format "Could not find '%s' node or index entry" 
+					    nodename-or-index))))))
     (message "Could not open: %s" name)))
 
 (provide 'org-info)
-- 
1.9.1