weasel

WebSocket-connected REPL environment for ClojureScript.

COMPATIBILITY NOTICE

Starting with Weasel 0.5.0, you will need at least ClojureScript version 0.0-2665 and Piggieback version 0.1.4. You may want to use Piggieback version 0.1.5-SNAPSHOT or newer, however, as it fixes a number of bugs related to the new ClojureScript REPL APIs.

why?

The traditional browser-connected REPL shipped with ClojureScript and Chas Emerick's refactored browser REPL Austin are both great ways to evaluate ClojureScript inside a running browser from a REPL. But since their communications go over an <iframe> transport via Closure's goog.net.xpc library, they can only be used in contexts that allow iframes and on pages which are served over the same protocol as the iframe (http://). This means you can't use these REPLs to connect to a page served off the filesystem (file://), in a Chrome extension (chrome-extension://), or as part of a Spotify Application (sp://). Weasel provides a REPL connection to these and similar environments.

usage

Weasel is intended to be used with Chas Emerick's piggieback nREPL middleware. Once you've set that up, add weasel as a dependency (available from Clojars) to your Leiningen project.clj:

[weasel "0.5.0"]

Start up lein repl and piggieback the Weasel REPL environment onto the nREPL session, optionally specifying a port (defaults to 9001) and an address to bind to (defaults to "127.0.0.1").

user> (require 'weasel.repl.websocket)
nil
user> (cemerick.piggieback/cljs-repl
        :repl-env (weasel.repl.websocket/repl-env
                   :ip "0.0.0.0" :port 9001))

<< started Weasel server on ws://0.0.0.0:9001 >>
Type `:cljs/quit` to stop the ClojureScript REPL
nil

In your project's ClojureScript, require the Weasel client namespace and connect to the REPL.

(ns my.cljs.core
  (:require [weasel.repl :as ws-repl]))

(ws-repl/connect "ws://localhost:9001")

You may optionally specify the following:

:verbose ; boolean, defaults to true
:print ; :repl to print only to the repl,
       ; :console to print only to the console
       ; #{:repl :console} to print to both
       ; or any variadic function to handle printing differently.
       ; defaults to :repl
:on-open, :on-error, :on-close ; fns for handling websocket lifecycle events.
                               ; default for all is nil

Connecting with options:

(ws-repl/connect "ws://localhost:9001"
   :verbose true
   :print #{:repl :console}
   :on-error #(print "Error! " %))

Load the page in your WebSocket-enabled environment (probably a browser) and start evaluating ClojureScript at the REPL:

cljs.user> (= (js/Number. 34) (js/Number. 34))
false
cljs.user> (do (js/alert "Hello world!") 42)
42

Note that unless a client is connected to the WebSocket channel, evaluation will fail:

cljs.user> (+ 5 10)
java.io.IOException: No client connected to Websocket
nil

Moreover, only a single browser can be connected to the REPL at once. Attempts to connect from another browser will fail with an error message in the browser's console. This may be addressed in future versions.

example

An example project is included in the weasel-example subdirectory of this project.

need help?