bug#1085: 23.0.60; all-completions, try-completion inconsistent: Info-read-node-name-1

["Drew Adams" <drew.adams@oracle.com>]

> From: Drew Adams Sent: Saturday, October 04, 2008 3:58 PM
>
> emacs -Q
> C-h i
>  
> M-: (try-completion "(el" 'Info-read-node-name-1)
>  
> It returns "(elisp)", meaning that this is the common prefix of all
> completions of "(el". [This is reasonable, and it satisfies the
> requirement that "(el" is a prefix of "(elisp)".]
>  
> M-: (all-completions "(el" 'Info-read-node-name-1)
>  
> It returns ("elisp"), meaning that the only valid completion of "(el"
> is "elisp". But "elisp" does not have the common prefix "(elisp)" as
> determined by `try-completion', and "elisp" does not even have the
> input "(el" as a prefix. This is inconsistent.  `all-completions'
> should return ("(elisp)") in this case.
>  
> Lisp code needs to be able to depend on the fact that the valid
> completions returned by `all-completions' have the common prefix
> that is returned by `try-completion' (which must in turn have the
> input as its prefix).
> 
> And each of the completions returned by `all-completions' must
> also satisfy `test-completion'.  In particular,
> (test-completion STRG (all-completions strg TABLE)) must always
> return t, for all STRG and TABLE. In this case, for STRG = "(el" and
> TABLE = `Info-read-node-name-1', it returns nil.
> 
> One should be able to use `all-completions' to construct a cons
> completion table that is equivalent to the original TABLE argument,
> regardless of how TABLE is defined (e.g. function, obarray).  That
> is, when used with the same inputs it should have the same effect,
> in particular for `try-completion', `all-completions', and
> `test-completion'.
> 
> I don't know if this is a bug for Info-read-node-name-1 (or -2) or a
> bug for one of the `minibuffer.el' functions that it uses.  The code
> is a bit hard to follow.
>  
> 
> In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
>  of 2008-10-03 on LENNART-69DE564
> Windowing system distributor `Microsoft Corp.', version 5.1.2600
> configured using `configure --with-gcc (3.4) --no-opt 
> --cflags -Ic:/g/include
> -fno-crossjumping'

FWIW, Emacs 22 also has the same problem, albeit differently:

(try-completion  "(el" 'Info-read-node-name-1) -> "(elisp"
(all-completions "(el" 'Info-read-node-name-1) -> ("elisp")

So the problem is likely not with the `minibuffer.el' code.

In GNU Emacs 22.3.1 (i386-mingw-nt5.1.2600)
 of 2008-09-06 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'