Subject: 29.3; Run time error in `dabbrev-completion'

From: Matt Armstrong <[email-masked]>
Date: Tue, 7 May 2024 12:19:43 -0700

I'm in a state where `dabbrev--last-buffer' is set to #<killed buffer>,
which confuses the `dabbrev-completion' command as shown by the 
backtrace below.

If I find a way to reproduce I will follow up with that.

I suspect that dabbrev.el should use `(buffer-live-p
dabbrev--last-buffer)' instead of checking for non-nil.

First, the value of dabbrev--last-buffer:

     dabbrev--last-buffer is a variable defined in ‘dabbrev.el’.
     Its value is #<killed buffer>
     Not documented as a variable.

Second, what happens when I run `dabbrev-completion':

Debugger entered--Lisp error: (error "Selecting deleted buffer")
   set-buffer(#<killed buffer>)
   (progn (set-buffer dabbrev--last-buffer))
   (if dabbrev--last-buffer (progn (set-buffer dabbrev--last-buffer)))
   (save-excursion (if dabbrev--last-buffer (progn (set-buffer 
dabbrev--last-buffer))) (or (and (not dabbrev-search-these-buffers-only) 
(>= direction 0) (setq dabbrev--last-direction (min 1 direction)) 
(dabbrev--try-find abbrev t (max 1 direction) ignore-case)) (and (or 
(not dabbrev-search-these-buffers-only) dabbrev--last-buffer) (<= 
direction 0) (setq dabbrev--last-direction -1) (dabbrev--try-find abbrev 
nil (max 1 (- direction)) ignore-case)) (progn (setq 
dabbrev--last-direction -1) (if dabbrev--last-buffer nil (if 
dabbrev--friend-buffer-list nil (setq dabbrev--friend-buffer-list 
(dabbrev--make-friend-buffer-list)) (setq dabbrev--progress-reporter 
(make-progress-reporter "Scanning for dabbrevs..." (- ...) 0 0 1 1.5)))) 
(let ((file-name (buffer-file-name)) file-name-buffer) (unwind-protect 
(progn (if file-name (progn ... ... ...)) (let (expansion) (while ... 
... ... ... ... ...) (progress-reporter-done dabbrev--progress-reporter) 
expansion)) (if (buffer-live-p file-name-buffer) (progn (kill-buffer 
file-name-buffer))) (setq dabbrev--friend-buffer-list (seq-filter 
#'buffer-live-p dabbrev--friend-buffer-list)))))))
   dabbrev--find-expansion("p" -1 t)
   dabbrev--find-all-expansions("p" t)
   #f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>)(#("p" 0 
1 (fontified t)) nil (boundaries . ""))
   completion-boundaries(#("p" 0 1 (fontified t)) #f(compiled-function 
(s p a) #<bytecode -0x1773fde4def7ae30>) nil "")
   completion-basic-try-completion(#("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1)
   #f(compiled-function (style) #<bytecode -0x1bb324416e7d7fbf>)(basic)
   completion--some(#f(compiled-function (style) #<bytecode 
-0x1bb324416e7d7fbf>) (basic partial-completion emacs22))
   completion--nth-completion(1 #("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1 
(metadata (cycle-sort-function . identity) (category . dabbrev)))
   completion-try-completion(#("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1 
(metadata (cycle-sort-function . identity) (category . dabbrev)))
   completion--do-completion(#<marker at 531 in persist.rs> 532)
   completion--in-region-1(#<marker at 531 in persist.rs> 532)
   #f(compiled-function (start end collection predicate) #<bytecode 
-0x16fb47f8fb6a4d3d>)(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   apply(#f(compiled-function (start end collection predicate) 
#<bytecode -0x16fb47f8fb6a4d3d>) (#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil))
   #f(compiled-function (funs global args) #<bytecode 
-0x73c1f01704730a2>)(nil nil (#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil))
   completion--in-region(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   completion-in-region(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   completion-at-point()
   dabbrev-completion(nil)
   funcall-interactively(dabbrev-completion nil)
   command-execute(dabbrev-completion)

In GNU Emacs 29.3 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.41,
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System Description: Debian GNU/Linux 12 (bookworm)

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