Scala sbt console - code changes not reflected in sbt console

Question

I use scala sbt console to test my methods. (commands : sbt then console) But the code changes done in eclipse or other external editor, are not getting reflected in the sbt console.

Every time, I have to quit the console (using Crt + D) and again start it using console command to see the changes.

Any one facing this problem? Is there any ways to reload the code from console?

I am using Ubuntu 64-Bit,

Audrieaudris

Answer 1

Not without using something like JRebel, mostly because class definitions could break in such a way as to make instances already loaded unusable. The only suggestion I have is to run the console with ~console so that if changes have been made they will be recompiled and the console re-entered.

Also if you're regularly running a set of commands the initialCommands sbt setting configures commands to be run immediately after starting the console.

Illfated

using sbt 0.13 the console does not restart automatically. Even more weird, then I get out of the console using exit, it recompiles and re-enters the console. – Limekiln

Adding the tilde just runs any command when the source code changes, but in the case of "console" it's still running until you exit it. – Illfated

Answer 2

One option is to use :restart in the console - this will reload it and replay all the commands you've entered so far.

For a better solution you might want to read my blog post on incremental development with JRebel & Scala.

You should modify the sbt startup script like this:

#!/bin/bash

java -noverify -javaagent:/home/username/path/to/jrebel/jrebel/jrebel.jar
 -Drebel.lift_plugin=true -XX:+CMSClassUnloadingEnabled
 -XX:MaxPermSize=512m -Xmx512M -Xss2M -jar `dirname $0`/sbt-launch.jar
 "$@"

When you start the REPL from inside SBT, for instance with the command:

sbt console

changes to the imported classes will be reflected automatically without the need to do a :replay or restart the REPL - something reminiscent of the interactive Lisp programming.

Craft

Thanks, This also helps. But we dont use jrebel now. – Audrieaudris

Since it's free for Scala development you might consider it. – Craft

Note that blog post requires a Maven continuous compile going in the background. If you're not using Maven, you can just open a second SBT process with an SBT continuous compile: ~; compile. – Glendoraglendower

Rather than modify the startup script, you might export SBT_OPTS from your global SBT config file at ~/.sbtconfig – Stopwatch

No :restart command on vanilla sbt. Does this require JRebel or something? – Ji