bug#67442: [PATCH] eglot: Add ruff-lsp as an alternative python server

["João Távora" <joaotavora@gmail.com>]

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On Sat, Nov 25, 2023, 13:01 Eli Zaretskii <eliz@gnu.org> wrote:

> > From: João Távora <joaotavora@gmail.com>
> > Date: Sat, 25 Nov 2023 12:39:22 +0000
> > Cc: Niall Dooley <dooleyn@gmail.com>, 67442@debbugs.gnu.org
> >
> > On Sat, Nov 25, 2023, 11:09 Eli Zaretskii <eliz@gnu.org> wrote:
> >
> >  > It supports surfacing Ruff diagnostics and providing Code Actions to
> >  > fix them, but is intended to be used alongside another Python LSP in
> >  > order to support features like navigation and autocompletion.
> >
> >  What do you mean by "alongside"?
> >
> >  João, does Eglot support such "alongside" servers?
> >
> > No. This is a feature on my to-do list, but alas I haven't had time to
> work on it.
>
> OK, thanks.  So AFAIU, we cannot install this change yet, right?
>

We can. If you read this patch it establishes ruff as an "alternative"
('eglot-alternative'), not as an "alongside" companion.

But just because we can doesn't mean we should. It's possible that the ruff
server wasn't meant to be a full alternative to those other servers.
Reading from its website hints ruff is mainly a linter, so it has a
fraction of what other servers have

The proponents of this patch should argue in terms of ruff-only LSP support
in python buffers. Maybe enough value that it's reasonable to install
as-is, maybe not and we should wait for 'eglot-alongside'.

Or just wait for someone to code a flymake-ruff backend in python-mode.el.
That seems much more promising way to get the intended ruff experience into
Emacs.

There is also the common misconception (not sure if the case here) that if
a server isn't mentioned in 'eglot-server-programs' directly then Eglot
doesn't support it. And this is far from the truth: if 'ruff' is installed
in a user's machine M-x eglot can easily be made to prompt for it. I've
tried dozens of servers like that.

João

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