bug#61748: 27.2; Eglot should use shell-file-name when launching the language server for a remote file

[Michael Albinus <michael.albinus@gmx.de>]

jeberger@free.fr writes:

Hi,

>>> # Partial fix
>>>
>>> The server starts correctly if I change function `eglot--cmd` to use `(or shell-file-name "sh")` instead of plain `"sh"`, e.g.:
>>
>> I don't think this is the correct fix.  The literal "sh -c" is used in
>> Eglot only for remote server invocations, and I presume this was done
>> to avoid the problems with running Eglot on MS-Windows.  Using
>> shell-file-name is incorrect for this use case because shell-file-name
>> gives you the name of the _local_ shell.  I think we have better ways
>> of dealing with this issue' I've CC'ed Michael in the hope that he
>> will tell how to solve this properly.
>>
>> Thanks.
>
> According to https://www.gnu.org/software/tramp/#Running-shell_002dcommand-on-a-remote-host
> `shell-file-name` is also used for _remote_ command invocation and set to `/bin/sh` by default.
> It can be configured using connection local variables. From the same source, the fix
> should also use `(or shell-command-switch "-c")` instead of plain `"-c"`.

Indeed. Since Tramp 2.4 (Emacs 27), Tramp provides both
`shell-file-name` and `shell-command-switch' as connection-local
variables. Per default, the former is "/bin/sh" (or "/system/bin/sh" on
Android devices).

When it is not known, whether a given remote buffer has expanded
connection-local variables, the usage pattern might be

(with-connection-local-variables shell-file-name)

> Cordially.

Best regards, Michael.