bug#34023: Support double colons in Info index entries

[Gavin Smith <gavinsmith0123@gmail.com>]

On Fri, Jan 11, 2019 at 02:04:32AM +0200, Juri Linkov wrote:
> The following patch handles the cases that you presented,
> but it's hard to predict what other cases it might break.
> 
> Do you have a sample test file that covers different cases?
> We could add such file to Emacs regression tests.

I've attached a file that includes different possibilities.

> I have to say that the current regexp-based parsing is
> an inherently fragile approach.  Do you think it would be possible
> to add more markup to Info files instead of relying on regexps?

I don't understand.  Whatever markup is added has to be read somehow, 
with regexp or other.

> Better yet would be to read Info manual in HTML format in Info reader.
> That would allow extracting all information unambiguously.

That would be a different project with several unresolved questions; this 
could be the way forward in the long term.  I would be opposed to making 
the standalone info program read HTML as this would be a complete 
rewrite of the program and there are probably better ways of dealing 
with it.


> diff --git a/lisp/info.el b/lisp/info.el
> index 6038273c37..2f7e293297 100644
> --- a/lisp/info.el
> +++ b/lisp/info.el
> @@ -2664,9 +2664,15 @@ Info-menu-entry-name-re
>  Because of ambiguities, this should be concatenated with something like
>  `:' and `Info-following-node-name-re'.")
>  
> +(defconst Info-index-entry-name-re "\\(?:[^:]\\|:[^,.;() \t\n]\\)*"
> +  "Regexp that matches an index entry name possibly including a colon.")
> +
>  (defun Info-extract-menu-node-name (&optional multi-line index-node)
>    (skip-chars-forward " \t\n")
> -  (when (looking-at (concat Info-menu-entry-name-re ":\\(:\\|"
> +  (when (looking-at (concat (if index-node
> +                                Info-index-entry-name-re
> +                                Info-menu-entry-name-re
> +                              ) ":\\(:\\|"
>  			    (Info-following-node-name-re
>                               (cond
>                                (index-node "^,\t\n")
> @@ -2741,7 +2747,9 @@ Info-complete-menu-item
>           (t
>            (let ((pattern (concat "\n\\* +\\("
>                                   (regexp-quote string)
> -                                 Info-menu-entry-name-re "\\):"
> +                                 (if (Info-index-node)
> +                                     Info-index-entry-name-re
> +                                   Info-menu-entry-name-re) "\\):"
>                                   Info-node-spec-re))
>                  completions
>                  (complete-nodes Info-complete-nodes))
> @@ -3966,7 +3974,8 @@ Info-try-follow-nearest-node
>  	      (setq node t))
>  	  (setq node nil))))
>       ;; menu item: node name
> -     ((setq node (Info-get-token (point) "\\* +" "\\* +\\([^:]*\\)::"))
> +     ((setq node (unless (Info-index-node)
> +                   (Info-get-token (point) "\\* +" "\\* +\\([^:]*\\)::")))
>        (Info-goto-node node fork))
>       ;; menu item: node name or index entry
>       ((Info-get-token (point) "\\* +" "\\* +\\(.*\\): ")
> @@ -4929,7 +4938,9 @@ Info-fontify-node
>          (let ((n 0)
>                cont)
>            (while (re-search-forward
> -                  (concat "^\\* Menu:\\|\\(?:^\\* +\\(" Info-menu-entry-name-re "\\)\\(:"
> +                  (concat "^\\* Menu:\\|\\(?:^\\* +\\(" (if (Info-index-node)
> +                                                            Info-index-entry-name-re
> +                                                          Info-menu-entry-name-re) "\\)\\(:"
>                            Info-node-spec-re "\\([ \t]*\\)\\)\\)")
>                    nil t)
>  	    (when (match-beginning 1)