Pttrt

Pttrt (/ˈpɪtrɪt/, or Pass Them To Run-time) is a sbt plugin, designed to pass data from compile-time to run-time.

Motive

Many times, my programs need some information, which is generated at compile-time and used at run-time. For example, Subversion's revision, JARs's dependencies, configuration files, and poor man's macro ;-), etc.

It is really heavyweight to deal with these situation in sbt. You need to create a plugin for each type of files you generated, to define many SettingKeys in each plugin's .scala files, and to set values for each of these SettingKeys in your .sbt files.

There are some plugins, like xsbt-reflect, also able to generate some infomation for run-time. But they cannot fit every variant cases I met. Another plugin, sbt-buildinfo has similar feature as Pttrt, but sbt-buildinfo cannot generate multiply files, preventing itself to be used for code generation from multiply separate plugins.

I just want a lightweight and general-purpose way like Makefile:

generated.properties:
	echo my.base.dir=$(PWD) > $@

That's why I created Pttrt.

Usage

Step 1: Install Pttrt into your project

Add the following line to your project/plugins.sbt:

addSbtPlugin("com.dongxiguo" % "pttrt" % "0.1.2")

And add pttrtSettings to your build.sbt:

pttrtSettings

Step 2: Export the data that will be passed to run-time

For example, if you want to know the building version on run-time, you need to add following lines at build.sbt:

pttrtSettings

version := "1.2.3-SNAPSHOT"

PttrtKeys.pttrtData <+= version map { v =>
  "org.yourHost.yourProject.YourSingleton" -> Map("Version" -> TypedExpression(v))
}

Step 3: Access the data on run-time

Create PttrtExample.scala:

object PttrtExample {
  def main(args: Array[String]) {
    println("Building version is " + org.yourHost.yourProject.YourSingleton.Version)
  }
}

Step 4: Run it!

$ sbt
> run-main PttrtExample

You will see:

Building version is 1.2.3-SNAPSHOT

See https://github.com/Atry/pttrt/tree/master/pttrt-test for more example.

Addition requirement

• Pttrt is for sbt 0.12
• Any value being passed to run-time must be a primary type (Int, Double, Boolean, etc) or java.io.Serializable
• The value's type must be found in the classpath for both compile-time and run-time.