bug#72088: eglot: Segregates language servers in a way that hampers polyglot language servers

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

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Major modes in eglot-server-programs don't work? What was attempted? I
couldn't understand. Look at existing examples, like C/C++ file types being
handled by the same server, and others.

João

On Sat, Jul 13, 2024, 07:16 Eli Zaretskii <eliz@gnu.org> wrote:

> > Date: Fri, 12 Jul 2024 13:33:56 +0200
> > From: Niels Thykier <niels@thykier.net>
> >
> > Hi
> >
> > Thanks for providing LSP support in emacs. :)
> >
> >
> > For reference, I used emacs 29.4 from Debian when I tested. If this
> > feature has changed in emacs 30, then I would not have seen it yet (I am
> > not tracking emacs/eglot development a lot).
> >
> >
> > I am working on a language server for Debian packaging (called
> > `debputy`). The Debian packaging files consists of several different
> > file formats with cross references between the formats. As a
> > consequence, I built my language server to be a "polyglot"
> (multi-language).
> >
> > While testing with eglot, I noticed that my language server was not
> > informed of all changes. As far as I can see, eglot spawns a language
> > server per file format (major mode) and then only informs the language
> > server of events (didOpen/didChange) for that major mode. This happens
> > even through it is exactly the same command + args for both major modes.
> >
> > The next result is that my language server when used via emacs + eglot,
> > requires the user to save a file before the language server can "see"
> > the effect when you are working in a different file.
> >
> > I was a bit in doubt whether the spec accounted for polyglot language
> > servers, so I asked in the LSP github for clarification. They made the
> > argument that a language server should be able to see events for other
> > file formats and suggested that I contacted you (the eglot maintainers)
> > about this
> > (https://github.com/microsoft/language-server-protocol/issues/1964).
> > They acknowledged this was implicit and then listed the two key features
> > they saw as supporting this implicit requirement (both of them boils
> > down to DocumentSelector as I read it).
> >
> > I tried a static registration with a DocumentSelector on `**/debian/*`
> > (I think it was hover docs, though it might have been completion), but
> > my debugging suggested that my instances did not get didOpen/didChange
> > events "across" the file formats even with this registration.
> >
> > Can we work towards a solution where I can ask eglot to provide
> > didOpen/didChange events across formats? :)
>
> João, any comments or suggestions?
>

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