REPL server

[dundalek]

Add some REPL server support so we can have closh backend and connect to it with different frontend readline implementations like omnia or rebel-readline.

It would be also cool to explore possibility to run REPL via clj CLI tool.

[mnewt]

This is not a difficult feature to add and would be very useful.

I propose that it work exactly like lumo. Copy pasting the relevant lines from lumo -h:

-d, --dumb-terminal          Disable line editing / VT100 terminal
                             control
-n opts, --socket-repl x     Enable a socket REPL where x is port, IP:port
                             or JSON of the following form, where port is
                             required:
                             {"host":   "localhost",
                              "port":   12345,
                              "accept": "some.namespaced.clojure/fn",
                              "args":   ["args", {"for": "the accept fn"}]}

That would allow for both relevant scenarios:

1. networked repl listening on a TCP port
2. repl running directly in a sub-process

@dundalek let me know if you are working on this. If not, I can do it.

[dundalek]

@mnewt I imagine eventually we might need some structured protocol like nREPL/prepl but socket repl is a good start. I didn't start working on this so it is up for grabs.

[mnewt]

OK, I'll work on it. I think socket repl is the standard for clojurescript for now. I think we should just implement that and worry about others once the clojurescript repl world stabilizes a bit.

I'm not aware of a clojurescript nREPL implementation. Is there one? prepl is interesting but still in development, and it will be interesting to see how the community uses it compared to unrepl.

[arichiardi]

Just a thought, is the idea to just launch lumo's socket repl? I think that it would be awesome to share implementation so that code would not be duplicated. Lumo accepts a function to it if you need to pre-parse the payloads.

[mnewt]

@arichiardi I hope to do something like that. In keeping with the rest of closh, I would expect that we would re-use as much of lumo's socket repl code as possible. I looked over lumo's source and it seems straightforward but I don't know the exact entry point and haven't tried to implement it yet.

[dundalek]

@arichiardi I haven't looked how lumo does it but if its true that your can pass a pre-process function to lumo and then launch it, that sounds like the simplest solution.

@mnewt You are right on both points, I don't know of a nREPL implementation in cljs either. It is doable but probably not the best investment of time. And I haven't been able to find any detailed description of prepl so I have no idea how it works.

Unrepl is a cool effort, but I am not convinced it has benefits to take over nREPL and adoption in community tooling seems to show that. I like the idea of wrapping around a socket repl. But if someone created a nREPL wrapper over socket repl, that would solve the main problem for me. Not sure what other benefits unrepl has.

[arichiardi]

So there is nRepl middleware but is Clojure specific.. it works for cljs but of course in very reduced fashion.

The main thing I would like to port to lumo is actually https://github.com/anmonteiro/lumo/issues/370.

That makes sense to me as first step.

[mnewt]

@arichiardi Is lumo.socketRepl.open() the entry point you had in mind?

I'm having trouble understanding how to load/call lumo's javascript modules from clojurescript (from inside lumo). Is the only way to first compile lumo to js and then require it? Can you give me any pointers?

[arichiardi]

Yes you got it right.

I was more thinking though that you can pass an accept function with the -n parameter on the command line. Do you have a requirement to call the js function?

[arichiardi]

This param: https://github.com/anmonteiro/lumo/blob/master/src/js/cli.js#L92

Sorry line was missing

[dundalek]

I am closing this since we now have a direct rebel-readline integration and nREPL server can also be started.