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

[Richard Kim <emacs18@gmail.com>]

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Nicolas,

Thanks for your feedback.  I agree that using the same link type is better.
Hence I took an alternate approach as detailed in the attached patch.
 Enhanced org-info-follow-link to attempt index lookup if node lookup fails.
Following is my check in message found in the attached patch:

    Enhanced org-info-follow-link to attempt index lookup if node lookup
fails.

    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.



On 6 November 2014 10:41, Nicolas Goaziou <mail@nicolasgoaziou.fr> wrote:

> Hello,
>
> Richard Kim <emacs18@gmail.com> writes:
>
> > A patch is provided below which implements a new link type called "infoi"
> > as a complement to "info" type that exist already.
>
> Thanks for your patch.
>
> > Why new link type?  Because info index is almost always finer grain
> > than info nodes.  For example [[infoi:libc#close]] brings up not only
> > "(libc)Opening and Closing Files" info node, but also place the cursor
> > on the line that documents "open" function within the node.  Hence it
> > is more useful to link function, variable and other names that are in
> > the index.  Most info documents have very rich indexes.
>
> OK. I would have preferred to merge both features into the same link
> type, but I see no elegant syntax to distinguish between a node and an
> index search.
>
> > I am not familiar with org coding style, so I share this patch to
> > present the idea rather than as a finished patch that can be checked
> > in.  I assume that name changes and other changes will be needed prior
> > to being acceptable for check in assuming that the idea is ok.
>
> The idea is OK. Some comments follow.
>
> > org-info.el: Add new link type "infoi" that looks up info file index.
>
> No full stop at the end of the summary.
>
> > * lisp/org-info.el (org-info-index-open): New function to implement
> > new link type named "infoi".
>
> "New function" is enough here.
>
> You can describe the motivation behind the patch farther in the commit
> message, after another blank line.
>
> > +;;; info-index
> > +
> > +(org-add-link-type "infoi" 'org-info-index-open)
> > +
> > +(declare-function Info-index "info" (topic))
> > +
> > +(defun org-info-index-open (name)
> > +  "Follow an Info file and look up index item specified by NAME."
> > +  (if (or (string-match "\\(.*\\)[#:]:?\\(.*\\)" name)
> > +          (string-match "\\(.*\\)" name))
> > +      (let ((nodename (match-string 2 name)))
> > +    (require 'info)
> > +    (Info-find-node (match-string 1 name) "Top")
> > +        (if nodename ; If there isn't a node, choose "Top"
> > +            (Info-index nodename)))
>
> Prefer `when' over one-armed `if'.
>
> > +    (message "Could not open: %s" name)))
>
> This introduce some code duplication in "org-info.el". Could you factor
> it out?
>
>
> Regards,
>
> --
> Nicolas Goaziou
>

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From c850804267f343d020f91499e18cbde84a3fb897 Mon Sep 17 00:00:00 2001
From: Kim <emacs18@gmail.com>
Date: Sun, 9 Nov 2014 19:43:18 -0800
Subject: [PATCH] Enhanced org-info-follow-link to attempt index lookup if node
 lookup fails.

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.
---
 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 db1490a..08e071d 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..7deaa33 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 (message "Could not find '%s' node or index entry." 
+					     nodename-or-index))))))
     (message "Could not open: %s" name)))
 
 (provide 'org-info)
-- 
1.9.1