Add the ability to “tail” the `*nrepl-server …*` buffer

[Josh-Tilles]

Given a situation like the following...

I'd like for the window showing the *nrepl-server …* buffer to scroll as new input comes in.
Here are a couple more screenshots that demonstrate the desired behavior vs. the actual behavior.

Desired outcome

# Actual outcome

[Malabarba]

Now that the server buffer keeps track of all clients, we could also just forward to all connection(repl) buffers any messages it receives (subject to a user option).

That should also be an easy elisp hack, if anyone wants to try. 😉

[bbatsov]

Yeah, probably this'd be best. I was musing over a similar solution a while back. I wonder, though, what's happening for people who're using cider-connect.

[expez]

This was implemented, discussed, and rejected previously #818

I ended up putting the pertinent code in my .emacs.d because I really wanted that functionality.

[bbatsov]

As I said before - the server buffer will never get "tail" functionality, but I'm pretty open to @Malabarba's idea to simply redirect the output to the matching REPL buffer. If memory serves I suggested something similar.

[Malabarba]

Yeah, probably this'd be best. I was musing over a similar solution a while back. I wonder, though, what's happening for people who're using cider-connect.

An ideal solution would be doing this in a middleware, instead of cider.el. Then people without a server buffer would benefit too. That said, either option would be a significant improvement on the current situation.

[bbatsov]

You can go over #818 for more details. I don't think this can be done using middleware as it seems that the output is dumped directly by the Clojure process and has nothing to do with nREPL. I haven't looked into this in a while, but I believe no one had ideas how to handle this reliably...

On the other hand this seems to work correctly with reply, although I'm not sure it will work correctly if you connect with reply to a running nREPL server.

[Malabarba]

It's not nREPL's fault, but the middleware can stil change the root value of #'*out*, can't it? Then the clojure process should respect that.

[bbatsov]

Hmm, something like this might work. We can probably send some init message to this middleware when cider launches. @cemerick does this sound sensible to you?

[bbatsov]

A bit more details about the proposed solution/workaround - https://gist.github.com/daviesian/4517859 & https://groups.google.com/forum/#!searchin/nrepl-el/log4j/nrepl-el/CSFOY27te6Q/BWM4xRnZ9ZoJ

[Malabarba]

Yeah, that gist is pretty much it. The middleware could also define a custom output stream that prints to all connected sessions, instead of just one.

[bbatsov]

Yeah, that sounds reasonable.

[cemerick]

Yes, one can bash away at *out*, and it'll be picked up transparently.

This whole issues is related to http://dev.clojure.org/jira/browse/NREPL-4, but that's a far more ambitious, fiddly undertaking.

[bbatsov]

Once clojure-emacs/cider-nrepl#257 is merged this will finally be resolved.

[bbatsov]

Guess now we can finally add the scrolling support.