bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Vivek Dasmohapatra]

[-- Attachment #1: Type: text/plain, Size: 10412 bytes --]

In an erc buffer, I tried to tab-complete a nick: The initial tab completion
showed many possibilities - I typed an extra character, which should have
limited it to a small enough number for tab-completion-cycling to kick in...
but instead TAB just unconditionally completed to the first of the remaining
candidates, and never offered me the chance to pick any of the others.

It turns out that pcomplete assumes that the interactive entry point
(activating command) can only ever be one of a handful of commands,
and specifically checks for those when deciding whether to enter the
code path that starts cycling through the remaining completions.

So modes that use pcomplete but define their own commands for tab completion
lose the ability to use pcomplete cycling unless they have
a way of adding themselves to the list of entry points that pcomplete
knows about.


In GNU Emacs 24.1.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.10)
 of 2012-08-23 on noise, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11204000
Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--build' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.1/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/x86_64-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars'
 'build_alias=x86_64-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LC_ALL: en_GB.UTF-8
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Diff

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  erc-truncate-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-services-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-netsplit-mode: t
  erc-match-mode: t
  erc-log-mode: t
  erc-pcomplete-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-autojoin-mode: t
  erc-move-to-prompt-mode: t
  auto-image-file-mode: t
  iswitchb-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<left> m a k e s SPC t h i n s g SPC <M-backspace> 
<M-backspace> <M-backspace> <M-backspace> <M-backspace> 
<down> <backspace> <up> <down> <backspace> <return> 
<up> <return> A t t a c h e d SPC p a t c h SPC h a 
s SPC b e e n SPC i n SPC u s e SPC h e r e SPC <M-backspace> 
<M-backspace> <M-backspace> <M-backspace> <M-backspace> 
f i x e s SPC t h e SPC p r o b l e m SPC f o r SPC 
m e SPC ( 0 <left> i n SPC e r c SPC <right> <backspace> 
) <left> <left> , SPC a n y w a y , SPC o t h e r SPC 
p c o m p l e t e <return> c a l l e r s <right> w 
o u l d SPC r e w q <backspace> <backspace> q u i r 
e SPC a SPC s i m i l a r SPC s m a l SPC f i x <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<backspace> : <down> <down> C-c C-c <up> <return> <tab> 
s m <tab> <return> <select-window> <select-window> 
<help-echo> <select-window> l o c <tab> <backspace> 
M-/ <M-backspace> <M-backspace> <M-backspace> <select-window> 
<down-mouse-1> <mouse-movement> <mouse-movement> <drag-mouse-1> 
<select-window> <help-echo> <help-echo> <select-window> 
l o c a l h o s t <return> <select-window> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <select-window> 
<help-echo> <down-mouse-1> <mouse-movement> <mouse-1> 
M-x r e p o r t <tab> <return>

Recent messages:
Sending...
Sending via mail...
Scanning for dabbrevs...done
Saving file /home/vivek/.emacs...
Wrote /home/vivek/.emacs [2 times]
Saving file /home/vivek/.emacs...
Wrote /home/vivek/.emacs [2 times]
Sending email 
Sending email done
Sending...done

Load-path shadows:
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/home/vivek/.emacs.d/lib/erc-page hides /usr/share/emacs/24.1/lisp/erc/erc-page
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/home/vivek/.emacs.d/lib/erc-imenu hides /usr/share/emacs/24.1/lisp/erc/erc-imenu
/home/vivek/.emacs.d/lib/erc-dcc hides /usr/share/emacs/24.1/lisp/erc/erc-dcc
/home/vivek/.emacs.d/lib/erc-backend hides /usr/share/emacs/24.1/lisp/erc/erc-backend
/home/vivek/.emacs.d/lib/erc-stamp hides /usr/share/emacs/24.1/lisp/erc/erc-stamp
/home/vivek/.emacs.d/lib/erc-services hides /usr/share/emacs/24.1/lisp/erc/erc-services
/home/vivek/.emacs.d/lib/erc-compat hides /usr/share/emacs/24.1/lisp/erc/erc-compat
/home/vivek/.emacs.d/lib/erc-autoaway hides /usr/share/emacs/24.1/lisp/erc/erc-autoaway
/home/vivek/.emacs.d/lib/erc-goodies hides /usr/share/emacs/24.1/lisp/erc/erc-goodies
/home/vivek/.emacs.d/lib/erc-notify hides /usr/share/emacs/24.1/lisp/erc/erc-notify
/home/vivek/.emacs.d/lib/erc-truncate hides /usr/share/emacs/24.1/lisp/erc/erc-truncate
/home/vivek/.emacs.d/lib/erc hides /usr/share/emacs/24.1/lisp/erc/erc
/home/vivek/.emacs.d/lib/erc-button hides /usr/share/emacs/24.1/lisp/erc/erc-button
/home/vivek/.emacs.d/lib/erc-log hides /usr/share/emacs/24.1/lisp/erc/erc-log
/home/vivek/.emacs.d/lib/erc-xdcc hides /usr/share/emacs/24.1/lisp/erc/erc-xdcc
/home/vivek/.emacs.d/lib/erc-match hides /usr/share/emacs/24.1/lisp/erc/erc-match
/home/vivek/.emacs.d/lib/erc-lang hides /usr/share/emacs/24.1/lisp/erc/erc-lang
/home/vivek/.emacs.d/lib/erc-netsplit hides /usr/share/emacs/24.1/lisp/erc/erc-netsplit
/home/vivek/.emacs.d/lib/erc-fill hides /usr/share/emacs/24.1/lisp/erc/erc-fill
/home/vivek/.emacs.d/lib/erc-track hides /usr/share/emacs/24.1/lisp/erc/erc-track
/home/vivek/.emacs.d/lib/erc-join hides /usr/share/emacs/24.1/lisp/erc/erc-join

Features:
(mailalias smtpmail qp shadow sort mail-extr emacsbug message rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mailabbrev gmm-utils mailheader
sendmail diff-mode conf-mode tramp-cache tramp-sh tramp tramp-compat
tramp-loaddefs mule-util info shell debug cus-edit js json imenu
newcomment jka-compr tabulated-list cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs vc-git texinfo
parse-time url-cache gtimelog hi-lock url-http url-gw mail-parse rfc2231
rfc2047 rfc2045 ietf-drums image-mode dired-aux dired edict
edict-japanese edict-english edict-morphology edict-edit dui-registry
dui multi-isearch etags apropos two-column iso-transl find-func dabbrev
gnutls network-stream starttls tls erc-truncate erc-track erc-services
erc-ring erc-networks erc-netsplit erc-match erc-log erc-pcomplete
pcomplete comint erc-button erc-fill erc-stamp erc-join erc-goodies erc
erc-backend erc-compat format-spec pp help-mode easymenu view regexp-opt
uniquify gnus gnus-ems nnheader mail-utils wid-edit image-file cus-start
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url-methods url-history url-cookie url-util url-parse auth-source eieio
byte-opt bytecomp byte-compile cconv macroexp assoc gnus-util
password-cache url-vars mm-util mail-prsvr mailcap ediff-merg ediff-diff
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derived ansi-color lui tracking edmacro kmacro flyspell ispell ring
incomplete debian-el debian-el-loaddefs magit-install emacs-goodies-el
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mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
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japanese hebrew greek romanian slovak czech european ethiopic indian
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[-- Attachment #2: possible fix + example of use in erc --]
[-- Type: text/x-diff, Size: 2136 bytes --]

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 01efd83..3917638 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -3964,7 +3964,9 @@ This places `point' just after the prompt, or at the beginning of the line."
     (kill-line)))
 
 (defun erc-complete-word-at-point ()
-  (run-hook-with-args-until-success 'erc-complete-functions))
+  (let ((pcomplete-extra-entry-points
+	 (cons 'completion-at-point pcomplete-extra-entry-points)))
+  (run-hook-with-args-until-success 'erc-complete-functions)))
 
 (define-obsolete-function-alias 'erc-complete-word 'completion-at-point "24.1")
 
diff --git a/lisp/pcomplete.el b/lisp/pcomplete.el
index 957505f..30a743b 100644
--- a/lisp/pcomplete.el
+++ b/lisp/pcomplete.el
@@ -471,6 +471,15 @@ Same as `pcomplete' but using the standard completion UI."
                           (plist-get :predicate (nthcdr 3 data)))))
 
 ;;; Pcomplete's native UI.
+(defvar pcomplete-extra-entry-points nil
+  "When an non-native command is driving `pcomplete', that command's
+symbol must be placed in this variable while `pcomplete' is invoked
+in order to allow completion cycling to occur.\n
+For example:\n
+  When completing ab → aba abc abd able via `completion-at-point',\n
+which [may] delegate to `pcomplete' via `completion-at-point-functions',
+the functions in that list should bind this variable to include the
+symbol 'completion-at-point.")
 
 ;;;###autoload
 (defun pcomplete (&optional interactively)
@@ -481,9 +490,10 @@ completion functions list (it should occur fairly early in the list)."
   (if (and interactively
 	   pcomplete-cycle-completions
 	   pcomplete-current-completions
-	   (memq last-command '(pcomplete
-				pcomplete-expand-and-complete
-				pcomplete-reverse)))
+           (or (memq last-command '(pcomplete
+                                    pcomplete-expand-and-complete
+                                    pcomplete-reverse))
+               (memq last-command pcomplete-extra-entry-points)))
       (progn
 	(delete-char (- pcomplete-last-completion-length))
 	(if (eq this-command 'pcomplete-reverse)

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Stefan Monnier]

> In an erc buffer, I tried to tab-complete a nick: The initial tab completion
> showed many possibilities - I typed an extra character, which should have
> limited it to a small enough number for tab-completion-cycling to kick in...
> but instead TAB just unconditionally completed to the first of the remaining
> candidates, and never offered me the chance to pick any of the others.

> It turns out that pcomplete assumes that the interactive entry point
> (activating command) can only ever be one of a handful of commands,
> and specifically checks for those when deciding whether to enter the
> code path that starts cycling through the remaining completions.

Hmm... but in Emacs-24.1, ERC does not use the `pcomplete' command to do
the completion but completion-at-point (which ends up calling
pcomplete-completions-at-point to get pcomplete to return the set of
completions).

So if cycling is to take place, it should presumably not be done by
pcomplete but by completion-at-point (e.g. obeying
completion-cycle-threshold).

IOW, I don't understand how your patch can fix your problem.
Can you provide a reproducible recipe starting from "emacs -Q"?


        Stefan

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Vivek Dasmohapatra]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1371 bytes --]

> So if cycling is to take place, it should presumably not be done by
> pcomplete but by completion-at-point (e.g. obeying
> completion-cycle-threshold).
>
> IOW, I don't understand how your patch can fix your problem.
> Can you provide a reproducible recipe starting from "emacs -Q"?

   emacs -Q

   customise the erc group, make sure erc-pcomplete is on (it
   should be)

   customise erc-complete-functions, add erc-pcomplete to
   the head of that list

   M-x erc RET … ; connect to freenode, enter #emacs

   j TAB ; big list of nicks beginning with jpops up

   l TAB ; unconditionally completes to whichever jl… nick
         ; was at the head of the list.

Analaysis:

   TAB                           → completion-at-point
   completion-at-point           → completion-at-point-functions
   completion-at-point-functions → erc-complete-word-at-point
   erc-complete-word-at-point    →
       (run-hook-with-args-until-success 'erc-complete-functions)
   erc-complete-functions        → erc-pcomplete
   erc-pcomplete                 → (call-interactively 'pcomplete)
   pcomplete                     →
       (memq last-command '(pcomplete
                            pcomplete-expand-and-complete
                            pcomplete-reverse)

   The above test controls entry into the cycling code.

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Stefan Monnier]

>   customise the erc group, make sure erc-pcomplete is on (it
>   should be)

Ah, that's the trick.  Any reason why you do that?  The default should
already give you almost the same behavior.

Also does the patch below fix your problem?


        Stefan


=== modified file 'lisp/erc/erc-pcomplete.el'
--- lisp/erc/erc-pcomplete.el	2013-01-02 16:13:04 +0000
+++ lisp/erc/erc-pcomplete.el	2013-09-13 13:30:27 +0000
@@ -82,10 +82,8 @@
   "Complete the nick before point."
   (interactive)
   (when (> (point) (erc-beg-of-input-line))
-    (let ((last-command (if (eq last-command 'erc-complete-word)
-                            'pcomplete
-                          last-command)))
-      (call-interactively 'pcomplete))
+    (setq this-command 'pcomplete)
+    (call-interactively 'pcomplete)
     t))
 
 ;;; Setup function

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Vivek Dasmohapatra]

On Fri, 13 Sep 2013, Stefan Monnier wrote:

>>   customise the erc group, make sure erc-pcomplete is on (it
>>   should be)
>
> Ah, that's the trick.  Any reason why you do that?  The default should
> already give you almost the same behavior.

It seems to always pop a buffer rather than cycling. Haven't
figured out why yet.

> Also does the patch below fix your problem?

Not tested yet, but it looks like it should work, yes.
Will confirm shortly.

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Vivek Dasmohapatra]

> Also does the patch below fix your problem?

Confirmed, restores tab-completion-cycling via erc-pcomplete.

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Stefan Monnier]

>>> customise the erc group, make sure erc-pcomplete is on (it
>>> should be)
>> Ah, that's the trick.  Any reason why you do that?  The default should
>> already give you almost the same behavior.
> It seems to always pop a buffer rather than cycling.
> Haven't figured out why yet.

Have you set completion-cycle-threshold?  If yes and it still doesn't
cycle, please post a recipe.


        Stefan

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Vivek Dasmohapatra]

> Have you set completion-cycle-threshold?  If yes and it still doesn't
> cycle, please post a recipe.

With the recipe as before, but _without_ erc-pcomplete at the head
of erc-complete-functions so the value is:

   '(erc-pcompletions-at-point erc-button-next-function)

And with completion-cycle-threshold set to 5, I get the following from 
repeatedly tabbing:

ERC> jlf: jlf_``: jlindsay: jlf: jlf_``: jlindsay: jlf:

so instead of cycling it's just adding the next element from the 
matching candidates list each time.

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Stefan Kangas]

Vivek Dasmohapatra <vivek@etla.org> writes:

>> Have you set completion-cycle-threshold?  If yes and it still doesn't
>> cycle, please post a recipe.
>
> With the recipe as before, but _without_ erc-pcomplete at the head
> of erc-complete-functions so the value is:
>
>   '(erc-pcompletions-at-point erc-button-next-function)
>
> And with completion-cycle-threshold set to 5, I get the following from
> repeatedly tabbing:
>
> ERC> jlf: jlf_``: jlindsay: jlf: jlf_``: jlindsay: jlf:
>
> so instead of cycling it's just adding the next element from the matching
> candidates list each time.

That was 6 years ago, and it seems like erc no longer uses pcomplete.
Are you still seeing this in a modern version of Emacs?

Best regards,
Stefan Kangas

bug#15362: 24.1; pcomplete unnecessarily restricts tab-completion entry points

[Stefan Kangas]

Stefan Kangas <stefan@marxist.se> writes:

> That was 6 years ago, and it seems like erc no longer uses pcomplete.
> Are you still seeing this in a modern version of Emacs?

More information was requested, but none was given within 4 weeks, so
I'm going to assume this has been fixed and close this bug.  If this is
still an issue, please reopen the bug report.

Best regards,
Stefan Kangas