GNU bug report logs - #79527
30.2; Cannot evaluate variable in literate-scratch-mode

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

From: Joost Kremers <joostkremers <at> fastmail.fm>
To: bug-gnu-emacs <at> gnu.org
Subject: 30.2; Cannot evaluate variable in literate-scratch-mode 
Date: Sun, 28 Sep 2025 10:52:13 +0200

In literate-scratch-mode (a GNU Elpa package), when I try to evaluate a
variable (e.g., `major-mode`) with `C-x C-e` or `C-j`, I get the following
error:

```
Debugger entered--Lisp error: (void-variable ajor-mode)
  (progn ajor-mode)
  eval((progn ajor-mode) t)
  elisp--eval-last-sexp(t)
  #f(compiled-function () #<bytecode 0xf49b74d6449a>)()
  eval-last-sexp(t)
  eval-print-last-sexp(nil)
  funcall-interactively(eval-print-last-sexp nil)
  command-execute(eval-print-last-sexp)
```

For some reason, the first character of the symbol is chopped off.

This is with Emacs 30.2 and the latest version of `literate-scratch-mode`
from GNU Elpa.

Recipe:

- Start Emacs with `emacs -Q -L ~/.emacs.d/elpa/literate-scratch-2.2/` (or
  wherever the package is installed).
- `M-: (require 'literate-scratch)`
- `M-x literate-scratch-mode` (in the *scratch* buffer, obviously).
- Type `major-mode` and press `C-x C-e` or `C-j`.

PS: if this isn't the right place to report bugs with GNU Elpa packages,
please let me know.

TIA

Joost Kremers




In GNU Emacs 30.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.50,
cairo version 1.18.4)
System Description: Arch Linux

Configured using:
 'configure --with-pgtk --sysconfdir=/etc --prefix=/usr
 --libexecdir=/usr/lib --localstatedir=/var --disable-build-details
 --with-cairo --with-harfbuzz --with-libsystemd --with-modules
 --with-native-compilation=aot --with-tree-sitter 'CFLAGS=-march=x86-64
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 'LDFLAGS=-Wl,-O1 -Wl,--sort-common -Wl,--as-needed -Wl,-z,relro -Wl,-z,now
 -Wl,-z,pack-relative-relocs -flto=auto' 'CXXFLAGS=-march=x86-64
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 -Wformat -Werror=format-security -fstack-clash-protection -fcf-protection
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 -Wp,-D_GLIBCXX_ASSERTIONS -g
 -ffile-prefix-map=/build/emacs/src=/usr/src/debug/emacs -flto=auto''
Configured features:
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LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER
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Important settings:
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  value of $XMODIFIERS: @im=ibus
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Major mode: mu4e:main

Minor modes in effect:
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Load-path shadows:
~/.emacs.d/lisp/custom hides /usr/share/emacs/30.2/lisp/custom
/home/joost/.emacs.d/elpa/transient-20250922.1438/transient hides /usr/share/emacs/30.2/lisp/transient
/home/joost/.emacs.d/elpa/which-key-20240620.2145/which-key hides /usr/share/emacs/30.2/lisp/which-key
/home/joost/.emacs.d/elpa/eglot-1.18/eglot hides /usr/share/emacs/30.2/lisp/progmodes/eglot
/home/joost/.emacs.d/elpa/eldoc-1.16.0/eldoc hides /usr/share/emacs/30.2/lisp/emacs-lisp/eldoc
/home/joost/.emacs.d/elpa/track-changes-1.4/track-changes hides /usr/share/emacs/30.2/lisp/emacs-lisp/track-changes

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Memory information:
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-- 
Joost Kremers
Life has its moments

Message #8 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Joost Kremers <joostkremers <at> fastmail.fm>
Cc: 79527 <at> debbugs.gnu.org
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Sun, 28 Sep 2025 11:47:35 +0200

On Sun, 28 Sep 2025 10:52:13 +0200 Joost Kremers <joostkremers <at> fastmail.fm> wrote:

> In literate-scratch-mode (a GNU Elpa package), when I try to evaluate a
> variable (e.g., `major-mode`) with `C-x C-e` or `C-j`, I get the following
> error:
>
> ```
> Debugger entered--Lisp error: (void-variable ajor-mode)
>   (progn ajor-mode)
>   eval((progn ajor-mode) t)
>   elisp--eval-last-sexp(t)
>   #f(compiled-function () #<bytecode 0xf49b74d6449a>)()
>   eval-last-sexp(t)
>   eval-print-last-sexp(nil)
>   funcall-interactively(eval-print-last-sexp nil)
>   command-execute(eval-print-last-sexp)
> ```
>
> For some reason, the first character of the symbol is chopped off.
>
> This is with Emacs 30.2 and the latest version of `literate-scratch-mode`
> from GNU Elpa.
>
> Recipe:
>
> - Start Emacs with `emacs -Q -L ~/.emacs.d/elpa/literate-scratch-2.2/` (or
>   wherever the package is installed).
> - `M-: (require 'literate-scratch)`
> - `M-x literate-scratch-mode` (in the *scratch* buffer, obviously).
> - Type `major-mode` and press `C-x C-e` or `C-j`.

If you point on the first "m" of `major-mode' and type `C-u C-x =',
you'll see near the bottom of the *Help* buffer that the character has
the `syntax-table' property (11), which means the comment-start syntax
class; when you enable literate-scratch-mode, this property is added by
`literate-scratch--put-comment-start', called from
`literate-scratch--propertize', which is the local value of
`syntax-propertize-function' set when literate-scratch-mode is enabled.
So "m" marks the line as a comment and "ajor-mode" is handled as Lisp
code, here a variable that hasn't been defined.

It looks like literate-scratch-mode treats plain text not beginning with
an open parenthesis as a comment (but I haven't examined the code in
detail).

Steve Berman 

Message #11 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Joost Kremers <joostkremers <at> fastmail.fm>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: 79527 <at> debbugs.gnu.org, spwhitton <at> spwhitton.name
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Sun, 28 Sep 2025 12:35:54 +0200

On Sun, Sep 28 2025, Stephen Berman wrote:
> If you point on the first "m" of `major-mode' and type `C-u C-x =',
> you'll see near the bottom of the *Help* buffer that the character has
> the `syntax-table' property (11), which means the comment-start syntax
> class; when you enable literate-scratch-mode, this property is added by
> `literate-scratch--put-comment-start', called from
> `literate-scratch--propertize', which is the local value of
> `syntax-propertize-function' set when literate-scratch-mode is enabled.
> So "m" marks the line as a comment and "ajor-mode" is handled as Lisp
> code, here a variable that hasn't been defined.

Thanks for the analysis, I hadn't thought of trying `C-u C-x =` or of
looking at the fontification...

> It looks like literate-scratch-mode treats plain text not beginning with
> an open parenthesis as a comment (but I haven't examined the code in
> detail).

Yes, that's basically what literate-scratch-mode is about: being able to
mix plain text with lisp code in the *scratch* buffer without it being
marked as an error or confusing things like paredit.

So I guess the question becomes: is this something that can be fixed, or is
it an unfortunate side-effect of the implementation that cannot be
mitigated?

[Cc:-ing Sean Whitton, in case he's not on this list.]

-- 
Joost Kremers
Life has its moments

Message #14 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Sean Whitton <spwhitton <at> spwhitton.name>
To: Joost Kremers <joostkremers <at> fastmail.fm>, Stefan Monnier
 <monnier <at> iro.umontreal.ca>
Cc: Stephen Berman <stephen.berman <at> gmx.net>, 79527 <at> debbugs.gnu.org
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Sun, 28 Sep 2025 18:19:20 +0100

Hello,

On Sun 28 Sep 2025 at 12:35pm +02, Joost Kremers wrote:

> On Sun, Sep 28 2025, Stephen Berman wrote:
>> If you point on the first "m" of `major-mode' and type `C-u C-x =',
>> you'll see near the bottom of the *Help* buffer that the character has
>> the `syntax-table' property (11), which means the comment-start syntax
>> class; when you enable literate-scratch-mode, this property is added by
>> `literate-scratch--put-comment-start', called from
>> `literate-scratch--propertize', which is the local value of
>> `syntax-propertize-function' set when literate-scratch-mode is enabled.
>> So "m" marks the line as a comment and "ajor-mode" is handled as Lisp
>> code, here a variable that hasn't been defined.
>
> Thanks for the analysis, I hadn't thought of trying `C-u C-x =` or of
> looking at the fontification...
>
>> It looks like literate-scratch-mode treats plain text not beginning with
>> an open parenthesis as a comment (but I haven't examined the code in
>> detail).
>
> Yes, that's basically what literate-scratch-mode is about: being able to
> mix plain text with lisp code in the *scratch* buffer without it being
> marked as an error or confusing things like paredit.
>
> So I guess the question becomes: is this something that can be fixed, or is
> it an unfortunate side-effect of the implementation that cannot be
> mitigated?

This is an interesting problem.  Thanks for reporting it.

Although the first character of the line is indeed marked as a comment
starter, that should mean that the syntax of the following characters is
comment, too, not Lisp.  So if something is handling "ajor-mode" as Lisp
code, it's doing the wrong thing.  It should handle the whole of
"major-mode" as a comment.  Then maybe C-j can't/shouldn't operate on
names of symbols embedded in comments, but that would be a different
problem.

So it seems like this reveals a bug in elisp--preceding-sexp, which is
what selects "ajor-mode" for evaluation.  We might be able to fix the
problem there.  Adding Stefan, who wrote that function.

> [Cc:-ing Sean Whitton, in case he's not on this list.]

I'm here, but it's good to CC people anyway so make sure they see it.

-- 
Sean Whitton

Message #17 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Sean Whitton <spwhitton <at> spwhitton.name>
Cc: Joost Kremers <joostkremers <at> fastmail.fm>, 79527 <at> debbugs.gnu.org,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Sun, 28 Sep 2025 19:43:49 +0200

On Sun, 28 Sep 2025 18:19:20 +0100 Sean Whitton <spwhitton <at> spwhitton.name> wrote:

> Hello,
>
> On Sun 28 Sep 2025 at 12:35pm +02, Joost Kremers wrote:
>
>> On Sun, Sep 28 2025, Stephen Berman wrote:
>>> If you point on the first "m" of `major-mode' and type `C-u C-x =',
>>> you'll see near the bottom of the *Help* buffer that the character has
>>> the `syntax-table' property (11), which means the comment-start syntax
>>> class; when you enable literate-scratch-mode, this property is added by
>>> `literate-scratch--put-comment-start', called from
>>> `literate-scratch--propertize', which is the local value of
>>> `syntax-propertize-function' set when literate-scratch-mode is enabled.
>>> So "m" marks the line as a comment and "ajor-mode" is handled as Lisp
>>> code, here a variable that hasn't been defined.
>>
>> Thanks for the analysis, I hadn't thought of trying `C-u C-x =` or of
>> looking at the fontification...
>>
>>> It looks like literate-scratch-mode treats plain text not beginning with
>>> an open parenthesis as a comment (but I haven't examined the code in
>>> detail).
>>
>> Yes, that's basically what literate-scratch-mode is about: being able to
>> mix plain text with lisp code in the *scratch* buffer without it being
>> marked as an error or confusing things like paredit.
>>
>> So I guess the question becomes: is this something that can be fixed, or is
>> it an unfortunate side-effect of the implementation that cannot be
>> mitigated?
>
> This is an interesting problem.  Thanks for reporting it.
>
> Although the first character of the line is indeed marked as a comment
> starter, that should mean that the syntax of the following characters is
> comment, too, not Lisp.  So if something is handling "ajor-mode" as Lisp
> code, it's doing the wrong thing.  It should handle the whole of
> "major-mode" as a comment.  Then maybe C-j can't/shouldn't operate on
> names of symbols embedded in comments, but that would be a different
> problem.
>
> So it seems like this reveals a bug in elisp--preceding-sexp, which is
> what selects "ajor-mode" for evaluation.  We might be able to fix the
> problem there.  Adding Stefan, who wrote that function.

With emacs -Q, I see that typing the line `;;major-mode' (without the
quotes) in *scratch* and then at the end of that line typing `C-x C-e'
displays `lisp-interaction-mode' in the echo area, but typing `C-j' at
the end of that line raises a Lisp error: (end-of-file #<buffer
*scratch*>) on calling `elisp--preceding-sexp'.

Steve Berman

Message #20 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Joost Kremers <joostkremers <at> fastmail.fm>
Cc: Stephen Berman <stephen.berman <at> gmx.net>, 79527 <at> debbugs.gnu.org,
 spwhitton <at> spwhitton.name
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Mon, 29 Sep 2025 15:04:58 -0400

> So I guess the question becomes: is this something that can be fixed,
> or is it an unfortunate side-effect of the implementation that cannot
> be mitigated?

It could be mitigated in various different ways, but yes it's an
unfortunate side-effect of the implementation, and any mitigation is
bound to be "hackish" (come with its set of downsides).

> With emacs -Q, I see that typing the line `;;major-mode' (without the
> quotes) in *scratch* and then at the end of that line typing `C-x C-e'
> displays `lisp-interaction-mode' in the echo area, but typing `C-j' at
> the end of that line raises a Lisp error: (end-of-file #<buffer
> *scratch*>) on calling `elisp--preceding-sexp'.

`eval-last-sexp` is a command meant to be usable anywhere rather than
only in ELisp buffers (e.g. can be used to run ELisp snippets in the
middle of an email message, or inside a string/comment, ...).
Maybe `eval-last-sexp` should be changed to ignore `syntax-table` text
properties, but then in elisp-mode buffers it would not benefit from the
refinement of `elisp-mode-syntax-propertize`.

As for `C-j`, it's a binding specific to `lisp-interaction-mode`.
If `literate-scratch-mode` uses the exact same command for `C-j` and
that command gets confused by `literate-scratch-mode`, then the problem
is on the side of `literate-scratch-mode`.  This said, it's not clear what
it *should* do when used on a non-code line, so it doesn't look like
a very serious problem.  Maybe the best fix would be to recognize that
it's a comment and signal a clear "C-j in a comment doesn't make
sense" error.


        Stefan

Message #23 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Sean Whitton <spwhitton <at> spwhitton.name>
To: Joost Kremers <joostkremers <at> fastmail.fm>
Cc: Stephen Berman <stephen.berman <at> gmx.net>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>, 79527 <at> debbugs.gnu.org
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Tue, 07 Oct 2025 16:54:16 +0100

Hello,

On Mon 29 Sep 2025 at 03:04pm -04, Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" wrote:

>> So I guess the question becomes: is this something that can be fixed,
>> or is it an unfortunate side-effect of the implementation that cannot
>> be mitigated?
>
> It could be mitigated in various different ways, but yes it's an
> unfortunate side-effect of the implementation, and any mitigation is
> bound to be "hackish" (come with its set of downsides).
>
>> With emacs -Q, I see that typing the line `;;major-mode' (without the
>> quotes) in *scratch* and then at the end of that line typing `C-x C-e'
>> displays `lisp-interaction-mode' in the echo area, but typing `C-j' at
>> the end of that line raises a Lisp error: (end-of-file #<buffer
>> *scratch*>) on calling `elisp--preceding-sexp'.
>
> `eval-last-sexp` is a command meant to be usable anywhere rather than
> only in ELisp buffers (e.g. can be used to run ELisp snippets in the
> middle of an email message, or inside a string/comment, ...).
> Maybe `eval-last-sexp` should be changed to ignore `syntax-table` text
> properties, but then in elisp-mode buffers it would not benefit from the
> refinement of `elisp-mode-syntax-propertize`.
>
> As for `C-j`, it's a binding specific to `lisp-interaction-mode`.
> If `literate-scratch-mode` uses the exact same command for `C-j` and
> that command gets confused by `literate-scratch-mode`, then the problem
> is on the side of `literate-scratch-mode`.  This said, it's not clear what
> it *should* do when used on a non-code line, so it doesn't look like
> a very serious problem.  Maybe the best fix would be to recognize that
> it's a comment and signal a clear "C-j in a comment doesn't make
> sense" error.

Thanks Stefan.  I'll have a look at elisp--preceding-sexp to see if
there is a way to change it that doesn't have downsides, though you're
probably right that there isn't.

If not I'll look into changing C-j, either the lisp-interaction-mode
binding, or giving it a separate binding in literate-scratch-mode.

Joost, I won't work on this immediately, so patches welcome if you're
interested.

-- 
Sean Whitton

Message #26 received at 79527 <at> debbugs.gnu.org (full text, mbox):

From: Joost Kremers <joostkremers <at> fastmail.fm>
To: Sean Whitton <spwhitton <at> spwhitton.name>
Cc: Stephen Berman <stephen.berman <at> gmx.net>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>, 79527 <at> debbugs.gnu.org
Subject: Re: bug#79527: 30.2; Cannot evaluate variable in literate-scratch-mode
Date: Tue, 07 Oct 2025 20:24:25 +0200

> Joost, I won't work on this immediately, so patches welcome if you're
> interested.

If I find some time, I might take a look. No promises, though.

-- 
Joost Kremers
Life has its moments

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