Testing sbt 1.0 cross builds

sbt 1.0 is now released, and everyone in the sbt community is hard at work upgrading their plugins. Because many sbt plugins depend on each other, there will be a short period of time (that we’re in now) where people won’t be able to upgrade their builds to sbt 1.0 because the plugins their builds use aren’t yet upgraded and released. However, that doesn’t mean you can’t cross build your plugin for sbt 1.0 now, simply upgrade to sbt 0.13.16 and use its sbt plugin cross building support.

I had a small problem yesterday though when working on the sbt-web upgrade, part of my plugin needed to be substantially rewritten for sbt 1.0 (sbt 1.0’s caching API now uses sjson-new rather than sbinary, so all the formats needed to be rewrittien). I didn’t want to rewrite this without an IDE because I knew nothing about sjson-new and needed to be able to easily browse and navigate its source code to discover how to use it, and I wanted the immediate feedback that IDEs give you on whether something will compile or not. The problem with doing this is that my build was still using sbt 0.13.16, and I couldn’t upgrade it because not all the plugins I depended on supported sbt 1.0. So, I came up with this small work around that I’m posting here for anyone that might find it useful, before reimporting the project into IntelliJ, I added the following configuration to my build.sbt:

sbtVersion in pluginCrossBuild := "1.0.0"
scalaVersion := "2.12.2"

Unfortunately it seems that you can’t leave this in the build file to ensure that sbt 1.0 is always the default, it seems that the sbt cross building support doesn’t override that setting (this is possibly a bug). But if you add that to your build.sbt right before you import into IntelliJ, then remove it later when you’re done developing for sbt 1.0, it’s a nice work around.

• sbt
• scala