Embed swank-js within existing node.js server

[mwolson]

Here are some changes I've made to support embedding swank-js within an existing node.js server, with the goal being to inspect and modify state within that server.

I'm looking for comments to see whether honing these changes is worth it. They're not usable as-is for the main repo, but if some of it were made configurable, it might be useful.

One change that could be taken by itself (with some modification) is limiting stacktrace output in errors so that it doesn't overwhelm Emacs REPL buffers.

Example for integrating into another server:

  var swank = require('swank-js');

  // Optionally start the swank REPL
  if (self.config.get('swank')) {
    if (self.config.get('swank:slime:enable')) {
      var swankPort = self.config.get('swank:slime:port') || 4005;
      swank.startSwankServer(swankPort);
      self.log.info('Swank SLIME server listening on http://localhost:' + swankPort);
    }
    if (self.config.get('swank:socketIO:enable')) {
      var socketIOPort = self.config.get('swank:socketIO:port') || 8009;
      swank.startSocketIOServer(socketIOPort);
      self.log.info('Swank socket.io server listening on http://localhost:' + socketIOPort);
    }
  }

[rksm]

Thanks for contributing! What's the difference to using require("swank-js/client/node").setupNodeJSClient();?

[mwolson]

The difference is that require("swank-js/client/node").setupNodeJSClient(); is a client for an existing server. Not a server in itself. So it didn't seem like it was capable of evaluating code within the global context of my app from SLIME.

[mwolson]

Another related thing I noticed was that in order to prevent SLIME from trying to launch the entire node.js process (instead of just connecting to it via TCP), I had to do this to make C-c C-z from a newly-opened .js file Just Work. Would be nice if there was a better way.

;; Node REPL using SLIME
(add-to-list 'load-path (concat my-emacs-path "/elisp/slime"))
(add-to-list 'load-path (concat my-emacs-path "/elisp/slime/contrib"))
(require 'slime)
(autoload 'slime-js-minor-mode "slime-js" nil t)
(add-hook 'js2-mode-hook
          (lambda ()
            (slime-js-minor-mode 1)))
(slime-setup '(slime-repl slime-js))
(setq slime-auto-connect 'always)
(setq slime-kill-without-query-p t)
(setq slime-protocol-version 'ignore)

(defun slime ()
  (interactive)
  (let ((process (slime-connect "localhost" 4005)))
    ;; Use "NODE" instead of nil in the REPL buffer name
    (setf (slime-connection-name process) "NODE")))

[wallyqs]

+1!
Is there something in particular that is holding this back? I just tried this, and it looks really useful! 👍

[jonnay]

Looks great! Thanks! can you update the wiki with some instructions?

Cheers!

[mwolson]

One thing to be aware of is that require() currently does not work with my patches, so may want to fix that before the next release. I'm thinking about plugging this into the built-in node.js REPL as a way of solving that. Possibly by taking a particular version of repl.js from node source and making small changes, possibly by just opening a socket to the one that comes with node.js.

[wallyqs]

I updated the wiki with some instructions on how I used it, hope this helps.
https://github.com/swank-js/swank-js/wiki/Embed-Swank-server-in-a-Node.js-application