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workbench 0.2.3

Example

A SBT plugin for scala-js projects to make development in the browser more pleasant.

  • Spins up a local web server on (by default) localhost:12345, whenever you're in the SBT console. Navigate to localhost:12345 in the browser and it'll show a simple page tell you it's alive. You can access any file within your project directory by going to localhost:12345/path/to/file in a browser.
  • Forwards all SBT logging from your SBT console to the browser console, so you can see what's going on (e.g. when the project is recompiling) without having to flip back and forth between browser and terminal.
  • Sends commands to tell the connected browsers to refresh/update every time your Scala.Js project completes a packageJS.

Check out the example app for a plug-and-play example of workbench in action.

Installation

  • Add to your project/plugins.sbt
resolvers += "spray repo" at "http://repo.spray.io"

resolvers += "Typesafe repository" at "http://repo.typesafe.com/typesafe/releases/"

addSbtPlugin("com.lihaoyi" % "workbench" % "0.2.3")
  • Add to your build.sbt
workbenchSettings

If you're using project/Build.scala or similar, also add:

import com.lihaoyi.workbench.Plugin._
  • So that workbench knows how to restart your application, specify a bootSnippet property in your SBT build, which is a javascript command to start your application, e.g.
bootSnippet := "ScalaJSExample().main();"
  • For all web pages you would like to integrate with workbench, add
<script type="text/javascript" src="/workbench.js"></script>

Usage

Once the above installation steps are completed, simply open your desired HTML file via http://localhost:12345 with the URL path being any file part relative to your project root. e.g. localhost:12345/target/scala-2.10/classes/index.html. This should serve up the HTML file and connect it to workbench.

Live Reloading

You have a choice of what you want to do when the code compiles.

refreshBrowsers

refreshBrowsers <<= refreshBrowsers.triggeredBy(packageJS in Compile)

This will to make any client browsers refresh every time packageJS completes, saving you flipping back and forth between SBT and the browser to refresh the page after compilation is finished.

updateBrowsers

updateBrowsers <<= updateBrowsers.triggeredBy(packageJS in Compile)

This will attempt to perform an update without refreshing the page every time fastOptJS completes. This involves:

  • Returning the state of document.body to the initial state before any javascript was run
  • Stripping all event listeners from things within body
  • Clearing all repeated timeouts and intervals
  • Running the bootSnippet again

updateBrowsers is a best-effort cleanup, and does not do things like:

  • clear up outstanding websocket/ajax connections
  • undo modifications done to window or document
  • mutations to global javascript objects

Nonetheless, for the bulk of javascript libraries these limitations are acceptable. As long as you're not doing anything too crazy, updateBrowsers but should suffice for most applications.

You can force the clean-up-and-reboot to happen from the browser via the shortcut Ctrl-Alt-Shift-Enter if you simply wish to reset the browser to a clean state.

spliceBrowsers

ScalaJSKeys.inliningMode := scala.scalajs.sbtplugin.InliningMode.Off

spliceBrowsers <<= spliceBrowsers.triggeredBy(ScalaJSKeys.fastOptJS in Compile)

This is an experimental feature that aims to perform an update to the code running in the browser without losing the state of the running code! Thus you can make changes to the code and have them immediately appear in the program, without having to restart and lose the current state of the application. See this video for a demo of it in action.

This live splicing is not doable in the general case, but only for some subset of changes:

  • Changes inside method bodies
  • Adding new defs and lazy vals to classes/objects
  • Creating entirely new classes/objects

This means that there are many changes that spliceBrowsers does not support, such as.

  • Adding new vals and vars to classes/objects
  • Modifying inheritance hierarchies
  • Changing the type of an existing val/var/lazy val
  • Renaming classes

And many more. If the change is something that Workbench does not support, you'll see errors in the browser console:

Example

And you'll need to refresh the page.

Note that you have to turn off the Scala.js inliner (as shown in the above SBT snippet) in order to have this work. The inliner performs inlinings across class and method boundaries that makes it hard to predict whether or not the live-splicer will work.

Lastly, note that spliceBrowsers does not retroactively modify the state of the application as if the changes in the code had always been present. For example, values set by the constructor in instances of a class will remain as-is even if you modify the class constructor; only new instances will be affected by the modified constructor.

In general, it is entirely possible to get into weird/invalid states due to this live-splicing, and the general solution is simply to refresh the page.

With this done, you should be receiving the SBT logspam (compilation, warnings, errors) in your browse console, and the page should be automatically refreshing/updating when the application gets recompiled. If you have problems setting this up, try starting from the example app and working from there.

Development

To develop, go into example/ and run sbt ~fastOptJS. Then you can go to

http://localhost:12345/target/scala-2.11/classes/index-dev.html

and see a small sierpinski-triangle application. Editing the code within example/ should cause the SBT log-spam to appear in the browser console, and changes (e.g. changing the color of the background fill) should cause a recompile and updating of the browser animation.

To make changes to workbench, modify the workbench source code and stop/re-run sbt ~fastOptJS. When workbench finishes re-compiling, SBT re-starts and the page becomes accessible, your changes to workbench will take effect. You can replace fullOptJs in the built.sbt file with fastOptJS, and swapping the reference to client-opt.js to client-fastopt.js, if you want to speed up the development cycle.

Pull requests welcome!

Change Log

##0.2.3

  • Upgraded uPickle, removed need for special resolver

##0.2.2

  • First implementation of spliceBrowsers

##0.2.1

  • Added missing resolver http://dl.bintray.com/non/maven

##0.2.0

  • First implementation of workbench client in Scala.js

##0.1.5

  • Properly kill the spray server on plugin unload, sbt reload now works
  • Swap out play-json with upickle
  • (Internally) separate Spray server code with SBT madness

License

The MIT License (MIT)

Copyright (c) 2013 Li Haoyi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.