GNU bug report logs - #76007
31.0.50; Interpreter not correctly found when using nix-shell.

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

From: Malcolm Purvis <malcolm <at> purvis.id.au>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; Interpreter not correctly found when using nix-shell.
Date: Sun, 02 Feb 2025 22:46:44 +1100

In NixOS if you want to use a script that manages its own 
dependencies, you use a command called "nix-shell" or "nix shell" 
to launch the script.

The start of such a script looks like:

#! /usr/bin/env nix-shell
#! nix-shell -i bash -p imagemagick cowsay

or

#! /usr/bin/env nix
#! nix shell github:tomberek/-#perlWith.HTMLTokeParserSimple.LWP 
  --command perl -x

The OS interpreter is nix-shell and nix-shell launches the real 
interpreter to execute the rest of the script.

With these scripts, Emacs's current behaviour is as follows:

- nix-shell is not interpreter-mode-alist so Emacs looks at the 
 file's 
extension:

- If the file has an extension then the correct mode is used
- If the file does not have an extension then Fundamental mode is 
used 
  regardless of the script's actual language.

If the file is a shell script with the correct extension, sh-mode 
is used but sh-mode fails to guess the shell, leaving the variable 
sh-shell as 'nix-shell.

In most cases this means that some shell features are not enabled, 
but otherwise it is possible to edit the script.

However, lsp-mode's bash language support (lsp-bash.el) throws an 
error if sh-shell is not set to it's supported values ('sh and 
'bash), and as a result nix bash scripts fail.

The solution is to add a new regexp to 
auto-mode-interpreter-regexp that will detect a nix script and 
extract the real interpreter from the second line.  Nix shell can 
be invoked in a number of ways but this regexp matches the common 
forms. 


diff --git a/lisp/files.el b/lisp/files.el
index 5ff40c335d7..1f3ac1431d2 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -3389,6 +3389,7 @@ and `inhibit-local-variables-suffixes'.  If
   "\\(?:[^ \t\n]+=[^ \t\n]*[ \t]+\\)*"
   "\\)?"
   "\\)?"
+   "\\(?:\\(?:nix\\|nix-shell\\)\n#![ 
\t]+\\(?:nix\\|nix-shell\\).*\\(?:-i\\|--command\\)[ \t]+\\)?"
   ;; Group 2: interpreter.  "\\([^ \t\n]+\\)")
  "Regexp matching interpreters, for file mode determination.


Malcolm


In GNU Emacs 31.0.50 (build 2, x86_64-apple-darwin24.2.0, NS
appkit-2575.30 Version 15.2 (Build 24C101)) of 2025-01-11 built on
lamechWindowing system distributor 'Apple', version 10.3.2575
System Description:  macOS 15.2

Configured using:
'configure 
--enable-locallisppath=/usr/local/share/emacs/site-lisp 
--infodir=/usr/local/Cellar/emacs-head <at> 31/31.0.50_1/share/info/emacs 
--prefix=/usr/local/Cellar/emacs-head <at> 31/31.0.50_1 --without-x 
--without-dbus --with-native-compilation --with-imagemagick 
--with-modules --with-gnutls --with-rsvg --with-xml2 
--with-xwidgets --with-webp --with-ns --disable-ns-self-contained 
'CFLAGS=-O2 -march=native -pipe -DFD_SETSIZE=10000 
-DDARWIN_UNLIMITED_SELECT' 'LDFLAGS=-L/usr/local/lib/gcc/14 
-I/usr/local/opt/gcc/include -I/usr/local/opt/libgccjit/include 
-I/usr/local/opt/gmp/include -I/usr/local/opt/jpeg/include''
 

-- 
		    Malcolm Purvis <malcolm <at> purvis.id.au> 

Message #8 received at 76007 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Malcolm Purvis <malcolm <at> purvis.id.au>, 76007 <at> debbugs.gnu.org
Subject: Re: bug#76007: 31.0.50;
 Interpreter not correctly found when using nix-shell.
Date: Sun, 2 Feb 2025 08:49:36 -0500

Malcolm Purvis <malcolm <at> purvis.id.au> writes:

> In NixOS if you want to use a script that manages its own
> dependencies, you use a command called "nix-shell" or "nix shell"
> to launch the script.
>
> The start of such a script looks like:
>
> #! /usr/bin/env nix-shell
> #! nix-shell -i bash -p imagemagick cowsay
>
> or
>
> #! /usr/bin/env nix
> #! nix shell github:tomberek/-#perlWith.HTMLTokeParserSimple.LWP
>    --command perl -x
>
> The OS interpreter is nix-shell and nix-shell launches the real
> interpreter to execute the rest of the script.
>
> With these scripts, Emacs's current behaviour is as follows:
>
> - nix-shell is not interpreter-mode-alist so Emacs looks at the
>   file's
>  extension:
>
>  - If the file has an extension then the correct mode is used
>  - If the file does not have an extension then Fundamental mode is
>  used
>    regardless of the script's actual language.
>
> If the file is a shell script with the correct extension, sh-mode
> is used but sh-mode fails to guess the shell, leaving the variable
> sh-shell as 'nix-shell.
>
> In most cases this means that some shell features are not enabled,
> but otherwise it is possible to edit the script.
>
> However, lsp-mode's bash language support (lsp-bash.el) throws an
> error if sh-shell is not set to it's supported values ('sh and
> 'bash), and as a result nix bash scripts fail.
>
> The solution is to add a new regexp to
> auto-mode-interpreter-regexp that will detect a nix script and
> extract the real interpreter from the second line.  Nix shell can
> be invoked in a number of ways but this regexp matches the common
> forms.
>
>
> diff --git a/lisp/files.el b/lisp/files.el
> index 5ff40c335d7..1f3ac1431d2 100644
> --- a/lisp/files.el
> +++ b/lisp/files.el
> @@ -3389,6 +3389,7 @@ and `inhibit-local-variables-suffixes'.  If
>     "\\(?:[^ \t\n]+=[^ \t\n]*[ \t]+\\)*"
>     "\\)?"
>     "\\)?"
> +   "\\(?:\\(?:nix\\|nix-shell\\)\n#![
> \t]+\\(?:nix\\|nix-shell\\).*\\(?:-i\\|--command\\)[ \t]+\\)?"
>     ;; Group 2: interpreter.  "\\([^ \t\n]+\\)")
>    "Regexp matching interpreters, for file mode determination.
>
>
> Malcolm

Thanks for the bug report.

This looks to me like a bug in lsp-mode, or lsp-bash.el.  I recommend
reporting the bug to them first.

Message #15 received at 76007-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Malcolm Purvis <malcolm <at> purvis.id.au>
Cc: 76007-done <at> debbugs.gnu.org
Subject: Re: bug#76007: 31.0.50;
 Interpreter not correctly found when using nix-shell.
Date: Sat, 1 Mar 2025 19:35:58 -0800

Stefan Kangas <stefankangas <at> gmail.com> writes:

> Malcolm Purvis <malcolm <at> purvis.id.au> writes:
>
>> In NixOS if you want to use a script that manages its own
>> dependencies, you use a command called "nix-shell" or "nix shell"
>> to launch the script.
>>
>> The start of such a script looks like:
>>
>> #! /usr/bin/env nix-shell
>> #! nix-shell -i bash -p imagemagick cowsay
>>
>> or
>>
>> #! /usr/bin/env nix
>> #! nix shell github:tomberek/-#perlWith.HTMLTokeParserSimple.LWP
>>    --command perl -x
>>
>> The OS interpreter is nix-shell and nix-shell launches the real
>> interpreter to execute the rest of the script.
>>
>> With these scripts, Emacs's current behaviour is as follows:
>>
>> - nix-shell is not interpreter-mode-alist so Emacs looks at the
>>   file's
>>  extension:
>>
>>  - If the file has an extension then the correct mode is used
>>  - If the file does not have an extension then Fundamental mode is
>>  used
>>    regardless of the script's actual language.
>>
>> If the file is a shell script with the correct extension, sh-mode
>> is used but sh-mode fails to guess the shell, leaving the variable
>> sh-shell as 'nix-shell.
>>
>> In most cases this means that some shell features are not enabled,
>> but otherwise it is possible to edit the script.
>>
>> However, lsp-mode's bash language support (lsp-bash.el) throws an
>> error if sh-shell is not set to it's supported values ('sh and
>> 'bash), and as a result nix bash scripts fail.
>>
>> The solution is to add a new regexp to
>> auto-mode-interpreter-regexp that will detect a nix script and
>> extract the real interpreter from the second line.  Nix shell can
>> be invoked in a number of ways but this regexp matches the common
>> forms.
>>
>>
>> diff --git a/lisp/files.el b/lisp/files.el
>> index 5ff40c335d7..1f3ac1431d2 100644
>> --- a/lisp/files.el
>> +++ b/lisp/files.el
>> @@ -3389,6 +3389,7 @@ and `inhibit-local-variables-suffixes'.  If
>>     "\\(?:[^ \t\n]+=[^ \t\n]*[ \t]+\\)*"
>>     "\\)?"
>>     "\\)?"
>> +   "\\(?:\\(?:nix\\|nix-shell\\)\n#![
>> \t]+\\(?:nix\\|nix-shell\\).*\\(?:-i\\|--command\\)[ \t]+\\)?"
>>     ;; Group 2: interpreter.  "\\([^ \t\n]+\\)")
>>    "Regexp matching interpreters, for file mode determination.
>>
>>
>> Malcolm
>
> Thanks for the bug report.
>
> This looks to me like a bug in lsp-mode, or lsp-bash.el.  I recommend
> reporting the bug to them first.

No further comments within 4 weeks, so I'm closing this bug.

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