C-h v fails when a symbol has variable documentation yet is unbound

C-h v fails when a symbol has variable documentation yet is unbound

[Alan Mackenzie]

When a symbol has variable documentation yet is unbound, "C-h v"'s
interactive specification prevents a user from displaying this
documentation.  This is not nice.

The variable I am thinking of is c-syntactic-context.  Normally, this
variable is unbound (indeed, MUST be unbound), but it gets dynamically
bound when calling auto-newline brace "action functions", auto-newline
semicolon/comma "criteria functions", "line-up" functions and
c-special-indent-hook-functions.  A user writing such a function should
be able to get c-syntactic-context's doc-string with C-h v.

The following patch fixes this.

 
2005-11-09  Alan Mackenzie  <acm@muc.de>

	* help-fns.el (describe-variable): Make C-h v work when a variable
	has variable documentation yet is unbound.


Index: help-fns.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/help-fns.el,v
retrieving revision 1.79
diff -c -r1.79 help-fns.el
*** help-fns.el	31 Oct 2005 17:06:00 -0000	1.79
--- help-fns.el	9 Nov 2005 11:18:25 -0000
***************
*** 496,502 ****
  				    (format
  				     "Describe variable (default %s): " v)
  				  "Describe variable: ")
! 				obarray 'boundp t nil nil
  				(if (symbolp v) (symbol-name v))))
       (list (if (equal val "")
  	       v (intern val)))))
--- 496,506 ----
  				    (format
  				     "Describe variable (default %s): " v)
  				  "Describe variable: ")
! 				obarray
! 				'(lambda (vv)
! 				   (or (boundp vv)
! 				       (get vv 'variable-documentation)))
! 				t nil nil
  				(if (symbolp v) (symbol-name v))))
       (list (if (equal val "")
  	       v (intern val)))))



-- 
Alan Mackenzie (Munich, Germany)

Re: C-h v fails when a symbol has variable documentation yet is unbound

[Stefan Monnier]

> When a symbol has variable documentation yet is unbound, "C-h v"'s
> interactive specification prevents a user from displaying this
> documentation.  This is not nice.

To get an unbound var with doc, you either have to do

   (defvar foo nil "doc")
   (makunbound 'foo)
or
   (put 'foo 'variable-documentation "doc")

both of which are rather ugly and feel like workarounds.
So I'm not sure how important this is.


        Stefan

Re: C-h v fails when a symbol has variable documentation yet is unbound

[Richard M. Stallman]

This change seems correct.  Would you please install it?

Meanwhile, why is it necessary for c-syntactic-context to be unbound
most of the time?  Couldn't it have some innocuous global value?

Re: C-h v fails when a symbol has variable documentation yet is unbound

[Alan Mackenzie]

Good Morning!

On Wed, 9 Nov 2005, Richard M. Stallman wrote:

>This change seems correct.  Would you please install it?

Done.  (My very first commission to the Emacs repository.  :-)

>Meanwhile, why is it necessary for c-syntactic-context to be unbound
>most of the time?  Couldn't it have some innocuous global value?

Hmm.  Thinking about it, yes, it could indeed have been nil.  There are
several places in CC Mode which test (boundp 'c-syntactic-context).  But
there might now also be code in derived modes which test this too.  So it
seems inadvisable to change it.

But it would have been better, right from ancient history, to have used
nil rather than unboundedness here.

-- 
Alan Mackenzie (Munich, Germany)