If anyone needs a project: Write a langserver for Racket: https://langserver.org/

@soegaard2 It looks like there are already at least two: https://pkgd.racket-lang.org/pkgn/search?tags=lsp

Ooh! Great.

Going to make remacs an LSP client?

That first pkg, an LSP server for the Racket lang, has some generic LSP implementation stuff that either a client or server could use. Maybe they’d be willing to split it out into a sep pkg.

Nice tip. Yes, long term I think implementing LSP would be a good thing. Lots of work in getting a racket-mode working. So not having to repeat the process for C, JavaScript, etc would be great.

Speaking of LSP-like stuff, the past few weeks I overhauled how racket-mode’s Emacs Lisp front end talks to the Racket back end over a TCP connection. The protocol is simply writing and reading s-expressions. :slightly_smiling_face: It used to be one write/read (request/response) at a time. I recently changed it to use a nonce/id and the responses can come at any time. So now multiple commands can be “in flight”, and a long one won’t block a shorter one. On the Emacs front-end there’s simply a hash-table of nonce -> callback function. So the basic command request/response approach now is “async”.

When it’s Emacs and Racket, simply writing/reading s-expressions is of course nice and something like JSON-RPC for LSP seems “heavy”. But in the general case of editors and langs, LSP seems fine and not that “heavy” compared to some specs I’ve seen.

Did you make the communication async to make the repl more robust? Or just to prevent blocking?

Two steps. 1. Few weeks ago, made the commands async to prevent blocking the Emacs UI. Worked well. 2. Then realized, something like racket-expand-file on a 1000 line file, the macro-debugger/stepper-text can take many seconds before you can even do the first step. Although it’s not blocking the Emacs UI generally, if you try another racket-mode command, of course that will be blocked. So then decoupled the requests and responses.

I’d thought of doing this for literally years, but the idea of command responses showing up async made me queasy. So I just needed time to think it through. Plus for long stretches wasn’t able to focus on anything complicated with racket-mode, due to other work.

I like your approach. Writing a repl is definitely more complicated than I expected.

It’s been an interesting journey, to do step by step. The first version of racket-mode just did a little syntax-highlighting fixes to scheme-mode, and dumped xrepl ,commands into a shell buffer, basically. :slightly_smiling_face:

Remacs (still need a better name) is progressing. I have basic highlighting, ] inserts matching parenthesis, indentation almost works (I think it works, but I need to fix a bug in the partial-parser). Now I am improving the actual repl.

It’s very helpful to look at racket-mode for Emacs.

Cool. Now that my “Summer of Emacs” commit-storm is winding down, I want to take a look at Remacs.

It’s still alpha-quality. The pieces are beginning to fell into plave though.

Are you able to use Remacs to edit Remacs yet? :slightly_smiling_face:

Nope!

That will be a nice :tada: milestone

I am impressed by the quality of the Emacs documentation.

I decided to keep the names used in the Emacs reference and mimic their operation closely.

Hmm, actually I’m a little confused how LSP is supposed to work with langs where you’d have both an edit buffer and a REPL. The LSP model seems to be, “Tell me, the LSP server, when you open a file and as you make changes to it in an edit buffer. I will keep a copy synchronized, so I know what to do when you give me commands.” In that model, what is a REPL? Is it like a second edit buffer? How are changes in it (like new definitions) supposed to be made known to the server if at all?

Anyway just an idle question. Some googling would probably answer.

Can’t find anything. It would be a natural thing to include repls in the tables on http://langserver.org\|langserver.org.

Have you checked out the two listed above?

One seems to be just having indentation and color. The other one, I couldn’t get it running on my machine.

I have been longing a lsp server for racket for a long time.

Would be nice too get them work on my machine.

Is there any good tutorial about functional programming patterns, especially for Racket?

@philip.mcgrath rather than rerunning raco setup, you can just run raco make blah.rkt

that will compile that file and all its dependencies

if the particular file you’re running has an out-of-date zo file, then raco setup will only fix that if your file is part of a collection somewhere

if not, raco setup won’t help

@greg That’s actually a very good question. It’s like we are keeping two set of states. I think it could at least work if we just keep the lsp server and repl separate. It’s actually interesting to think the repl as a edit buffer, but maybe it’s a buffer that you can only add stuff, and not update or delete anything, I think. In that case it might not be very useful for the lsp server.

There are already lsp server for CL and clojure though. I’m interested in how they tackle this.