SBT plugin that complements the pio build command.

This is a very simple plugin that provides a new build settings to all engine templates: pioVersion.

Every engine template used to have a build.sbt file with PredictionIO version hard-coded, e.g.

libraryDependencies ++= Seq(
  "io.prediction"    %% "core"        % "0.8.6" % "provided",
  "org.apache.spark" %% "spark-core"  % "1.2.0" % "provided",
  "org.apache.spark" %% "spark-mllib" % "1.2.0" % "provided")

When one builds an engine template (pio build) with a mismatched version of PredictionIO, such as 0.9.0, the build process will succeed without error. When doing pio train, however, strange errors could occur, such as the infamous java.lang.AbstractMethodError, with no useful information for debugging.

When pio build is run, it automatically generates a pio.sbt file at the engine's project root directory before building the engine. The file sets pioVersion to the correct value. Engine templates can use this value instead of a hard coded one, e.g.

libraryDependencies ++= Seq(
  "io.prediction"    %% "core"        % pioVersion.value % "provided",
  "org.apache.spark" %% "spark-core"  % "1.2.0"          % "provided",
  "org.apache.spark" %% "spark-mllib" % "1.2.0"          % "provided")

Add the following to your engine template's project/pio-build.sbt

addSbtPlugin("io.prediction" % "pio-build" % "0.9.0")

and modify your engine template's build.sbt to use pioVersion as shown above.