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bug#49163: 28.0.50; Dynbind add-function and lambdas as file vars
From: |
Michael Heerdegen |
Subject: |
bug#49163: 28.0.50; Dynbind add-function and lambdas as file vars |
Date: |
Tue, 22 Jun 2021 01:16:50 +0200 |
Hello,
this is the second time I have stumbled across this and it is annoying -
so here is the story:
The template of the code I was using is like this:
#+begin_src emacs-lisp
;; -*- lexical-binding: t -*-
(defun test ()
(interactive)
(funcall (or my-do-with-test-process-fun #'identity)
(start-process "test-process" "foo" "xterm")))
(defvar my-do-with-test-process-fun nil)
#+end_src
I want to use `my-do-with-test-process-fun' as a file local variable. I
try like this:
testfile.txt:
| File contents ...
| ...
|
| Local Variables:
| my-do-with-test-process-fun: (lambda (p) (add-function :before
(process-sentinel p) (lambda (&rest _) (message "Test"))))
| End:
(I hope mailing stuff doesn't break the overlong line defining
`my-do-with-test-process-fun'.)
When I open that file and try M-x test I get this error:
| Debugger entered--Lisp error: (void-variable #:v)
| (process-sentinel #:v)
| (lambda nil (process-sentinel #:v))()
| advice--add-function(:before ((lambda nil (process-sentinel #:v)) lambda
(gv--val) (set-process-sentinel #:v gv--val)) (lambda (&rest _) (message
"Test")) nil)
| (add-function :before (process-sentinel p) (lambda (&rest _) (message
"Test")))
| (lambda (p) (add-function :before (process-sentinel p) (lambda (&rest _)
(message "Test"))))(#<process test-process>)
| funcall((lambda (p) (add-function :before (process-sentinel p) (lambda
(&rest _) (message "Test")))) #<process test-process>)
| test()
(1) I suspect that this happens because the lack of lexical binding
"somewhere". Enabling lexical binding mode in `testfile.txt' alone
doesn't help. OTOH, setting the file local variable like this:
| Local Variables:
| eval: (setq-local my-do-with-test-process-fun (eval (lambda (p) (add-function
...) t)))
| End:
makes `M-x test` work. Is this all expected so far?
(2) If lack of lexical binding is the culprit: I see that `add-function'
uses `gv-ref' and that warns about uses in dynamically binding Elisp.
Should `add-function' warn about such a restriction as well?
(3) And I wonder: now that lexical binding Elisp gets more common,
should file local variables be set using a lexically binding environment
-- or at least when the file itself specifies lexical binding mode?
TIA,
Michael.
In GNU Emacs 28.0.50 (build 15, x86_64-pc-linux-gnu, GTK+ Version 3.24.24,
cairo version 1.16.0)
of 2021-06-21 built on drachen
Repository revision: 50a59b9af1517f24fca60feab37140f2b35ea5ac
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Debian GNU/Linux bullseye/sid
Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBSELINUX LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP
SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB
Important settings:
value of $LC_ALL: de_DE.utf8
value of $LC_COLLATE: C
value of $LC_TIME: C
value of $LANG: de_DE.utf8
locale-coding-system: utf-8-unix
- bug#49163: 28.0.50; Dynbind add-function and lambdas as file vars,
Michael Heerdegen <=