Re: New jrpc.el JSONRPC library

[joaotavora@gmail.com (João Távora)]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: João Távora <joaotavora@gmail.com>
>> Cc: emacs-devel@gnu.org, monnier@iro.umontreal.ca, vibhavp@gmail.com
>> Date: Fri, 18 May 2018 17:27:54 +0100
>> 
>> So, off-list Stefan likewise suggested that some level of LSP
>> "infrastructure" is integrated into Emacs, which could lead to merging
>> eglot.el and other LSP clients like lsp-mode.el in the future.
>> 
>> As JSONRPC support is a mandatory component of LSP, I've extracted a
>> library implementing the JSONRPC spec (see www.jsonrpc.org) out of
>> eglot.el.
>> 
>> I propose this library, jrpc.el, for Emacs core (or GNU ELPA, or
>> both). I hope people can review it, comment on it, and propose changes,
>> particularly developers of other existing LSP-modes.  I attach to the
>> end of this mail with a reasonably complete ";;; Commentary" header,
>> including a simple usage example.
>> 
>> JSONRPC is apparently also used for other non-LSP applications. See
>> http://json-rpc.info/.
>
> Thanks, this sounds like a good addition.  Does it (or can it) work
> with the built-in JSON support we have on the master branch?

Not yet. I didn't know about that, but indeed it has to be on the
roadmap, so I'll start looking into it.

> And I still wonder whether more of eglot's LSP support should be in
> core.  After all, only customizing LSP for a specific language should
> be left for the major modes, the rest of interaction with LSP is
> probably language-agnostic, right?

In fact, no. At least not ideally. *All* of LSP is
language-agnostic. The only two things eglot.el does mode-locally are:

1. a very small tweak for `rust-mode', whose not-entirely-compliant RLS
   server has some trouble that eglot works around and

2. a global `eglot-server-programs' variable mapping major-modes to
   server-launching commands.

The first should go into rust-mode.el (not currently in Emacs/ELPA). The
second one could be replaced by a (setq eglot-server-program <program>)
int he mode hook.

So again, if LSP support is wanted, eglot.el fits that bill (and better
that others IMNSHO :-) But I'd let it mature out of core for a little
while more.

João