bug#591: 23.0.60; lisp-complete-symbol erases extra text

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

> From: Stefan Monnier Sent: Tuesday, July 29, 2008 3:08 PM
> > Hi Stefan, This bug was introduced by your patch:
> 
> Yes, I know.
> 
> > This sets completion-base-size to 0, which causes the completions
> > buffer to delete everything in the Lisp buffer when you make a
> > selection.
> 
> The problem is that leaving it nil will revert to the use of
> a heuristic.  Fixing it right is a bit more difficult.
> 
> > I don't understand why we need the (completely undocumented) hack
> > introduced here, where the cdr of the last item on the 
> > completions list gives completion-base-size.  Does anything else
> > in Emacs depend on this? Why not simply add a new optional
> > argument to display-completion-list?
> 
> Yes the base-size in the cdr is a hack, and we be able to get 
> rid of it now that I've added the new `boundaries' action.  But
> passing it as an additional argument won't make any difference for
> the bug at hand.

This hack still seems to be present in the code from a build today:

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'

The cdr still seems to be used for the base size.

 From completion-all-completions:

  (let ((completion-all-completions-with-base-size t))

 From completion-table-with-context:

  ;; In case of non-empty all-completions,
  ;; add the prefix size to the base-size.
  ((consp comp)
   (let ((last (last comp)))
     (when completion-all-completions-with-base-size
       (setcdr last (+ (or (cdr last) 0) (length prefix))))
     comp))

 From completion--file-name-table:

  (if (and completion-all-completions-with-base-size (consp all))
      ;; Add base-size, but only if the list is non-empty.
      (nconc all base-size)
    all)

This hack prevents code from treating the list as a true list - e.g. applying
`length' to it. If, as you say, the hack is no longer needed and we are "able to
get rid of it now", could you please remove it?

Also, there is still no doc string for some of the more important functions in
this library - e.g. completion-table-with-context,
completion-table-with-terminator, completion-all-sorted-completions,
completion-hilit-commonality, completion-basic-try-completion,
completion-basic-all-completions, completion-pcm-all-completions,
completion-pcm-try-completion.

Likewise, no doc string for less important functions - e.g.
completion--try-word-completion, minibuffer--bitset,
completion--flush-all-sorted-completions, minibuffer--double-dollars,
completion--make-envvar-table, completion--embedded-envvar-table,
completion-emacs21-try-completion, completion-emacs21-all-completions,
completion-emacs22-try-completion, completion-emacs22-all-completions,
completion-pcm--prepare-delim-re, completion-pcm--pattern-trivial-p,
completion-pcm--pattern->regex, completion-pcm--hilit-commonality,
completion-pcm--pattern->string, completion-pcm--merge-try.

Likewise, no doc string for variables - e.g. completion-all-sorted-completions,
completion-common-substring, completion--embedded-envvar-re,
completion-pcm--delim-wild-regex.

Thx.