GNU bug report logs - #20139
25.0.50; eval-buffer ignores lexical-binding

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jorgen Schaefer <contact <at> jorgenschaefer.de>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.50; eval-buffer ignores lexical-binding
Date: Wed, 18 Mar 2015 23:09:04 +0100

Given a buffer with these contents:

(setq lexical-binding t)
(message "%s" (lambda () a))

Evaluating both lines with C-x C-e will message (closure (t) nil a), as
it should. But M-x eval-buffer will message (lambda nil a), i.e.
eval-buffer ignores the value of lexical-binding.

I do not think this is the intended behavior :-)

Regards,
Jorgen

In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu)
 of 2015-02-21 on loki.jorgenschaefer.de
Repository revision: 9074a684990600abd9dfad0477c7cd1d2f339ed3
System Description:	Debian GNU/Linux 7.8 (wheezy)

Configured using:
 `configure --without-x'

Message #8 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Jorgen Schaefer <contact <at> jorgenschaefer.de>
Cc: 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Wed, 18 Mar 2015 23:10:30 -0400

> (setq lexical-binding t)
> (message "%s" (lambda () a))

This is wrong.  The `setq' above is an expression evaluated at run-time,
whereas what you want to say (that this code is written in the lexical
version of the Elisp language) is something that needs to be known before
evaluation proceeds.

You can do M-: (setq lexical-binding t) from that buffer in order to
tell Emacs that the code in the buffer uses the lexical
version of the Elisp language, or better, you should put a "-*-
lexical-binding:t -*-" at the top of the file.


        Stefan

Message #11 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Jorgen Schäfer <contact <at> jorgenschaefer.de>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 08:33:52 +0100

On Thu, Mar 19, 2015 at 4:10 AM, Stefan Monnier
<monnier <at> iro.umontreal.ca> wrote:
>> (setq lexical-binding t)
>> (message "%s" (lambda () a))
>
> This is wrong.  The `setq' above is an expression evaluated at run-time,
> whereas what you want to say (that this code is written in the lexical
> version of the Elisp language) is something that needs to be known before
> evaluation proceeds.

I am sorry for the confusion; I added the `setq' form so it is easier
to C-x C-e it. The
bug I describe happens in a buffer with `lexical-binding' set, no
matter which way it
is set. I.e. the following snippet will message (lambda nil t) and
then (closure (t) nil t):

(with-temp-buffer
  (setq lexical-binding t)
  (insert "(message \"%S\" (lambda () t))")
  (eval-buffer)
  (eval-region (point-min) (point-max)))

Regards,
Jorgen

Message #14 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Nicolas Richard <theonewiththeevillook <at> yahoo.fr>
To: Jorgen Schäfer <contact <at> jorgenschaefer.de>
Cc: 20139 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 10:56:37 +0100

Jorgen Schäfer <contact <at> jorgenschaefer.de> writes:
> . I.e. the following snippet will message (lambda nil t) and
> then (closure (t) nil t):
>
> (with-temp-buffer
>   (setq lexical-binding t)
>   (insert "(message \"%S\" (lambda () t))")
>   (eval-buffer)
>   (eval-region (point-min) (point-max)))

And this will reverse the behaviour :
(with-temp-buffer
  (insert ";; -*- lexical-binding: t; -*-\n(message \"%S\" (lambda () t))")
  (eval-buffer)
  (eval-region (point-min) (point-max)))

IOW eval-buffer obeys the "file"-local variable by calling
    specbind (Qlexical_binding, lisp_file_lexically_bound_p (buf) ? Qt : Qnil);
while eval-region simply uses the current value of lexical-binding.

-- 
Nicolas

Message #17 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Nicolas Richard <theonewiththeevillook <at> yahoo.fr>
Cc: Jorgen Schäfer <contact <at> jorgenschaefer.de>,
 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 10:15:29 -0400

> IOW eval-buffer obeys the "file"-local variable by calling
>     specbind (Qlexical_binding, lisp_file_lexically_bound_p (buf) ? Qt : Qnil);
> while eval-region simply uses the current value of lexical-binding.

Indeed, and I don't think we can easily change either of these.
Jorgen, what is the original problem you're trying to solve?


        Stefan

Message #20 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Jorgen Schäfer <contact <at> jorgenschaefer.de>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>, 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 15:52:11 +0100

On Thu, Mar 19, 2015 at 3:40 PM, Stefan Monnier
<monnier <at> iro.umontreal.ca> wrote:
>> I am extracting Emacs Lisp code from a markdown file and evaluating
>> it. I can easily use eval-region instead of eval-buffer, so I have no
>> unsolved problem at the moment. Just figured I'd report this issue.
>
> The basic rule for me is "never (setq lexical-binding ...)".  Instead,
> either add the file-local magic marker and manipulate it as a whole
> buffer/file, or let-bind lexical-binding around the call to
> `eval-region', or pass the second arg to `eval'.

Let-binding `lexical-binding' does not affect `eval-buffer', either.

(with-temp-buffer
  (let ((lexical-binding t))
    (insert "(message \"%S\" (lambda () t))")
    (eval-buffer)
    (eval-region (point-min) (point-max))))

(lambda nil t)
(closure (t) nil t)

Regards,
Jorgen

Message #23 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Cc: Jorgen Schaefer <contact <at> jorgenschaefer.de>, 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 11:49:17 -0400

Stefan Monnier wrote:

> You can do M-: (setq lexical-binding t) from that buffer in order to
> tell Emacs that the code in the buffer uses the lexical

Apparently that doesn't work: http://debbugs.gnu.org/15070

Message #28 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Jorgen Schäfer <contact <at> jorgenschaefer.de>
Cc: 20139 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Thu, 19 Mar 2015 12:28:52 -0400

>> The basic rule for me is "never (setq lexical-binding ...)".  Instead,
>> either add the file-local magic marker and manipulate it as a whole
>> buffer/file, or let-bind lexical-binding around the call to
>> `eval-region', or pass the second arg to `eval'.
> Let-binding `lexical-binding' does not affect `eval-buffer', either.

Yes: note that I distinguish between "whole buffer/file" and the other
case (the other case being when you evaluate some chunk of code).


        Stefan

Message #31 received at 20139 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Cc: Jorgen Schäfer <contact <at> jorgenschaefer.de>,
 Nicolas Richard <theonewiththeevillook <at> yahoo.fr>, 20139 <at> debbugs.gnu.org,
 15070 <at> debbugs.gnu.org
Subject: Re: bug#20139: 25.0.50; eval-buffer ignores lexical-binding
Date: Mon, 07 Oct 2019 17:25:28 +0200

Stefan Monnier <monnier <at> IRO.UMontreal.CA> writes:

>> IOW eval-buffer obeys the "file"-local variable by calling
>>     specbind (Qlexical_binding, lisp_file_lexically_bound_p (buf) ?
>> Qt : Qnil);
>> while eval-region simply uses the current value of lexical-binding.
>
> Indeed, and I don't think we can easily change either of these.
> Jorgen, what is the original problem you're trying to solve?

So `eval-buffer' ignores the buffer-local value of `lexical-binding',
and that's a feature.  So I think we should just document that?

I've now done so in Emacs 27.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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