PC Plod is a testing library for macro and compiler plugin authors to make assertions of their libraries in the Presentation Compiler, i.e. ENSIME and Scala IDE.

Installation

Published as a regular artefact, the sbt installation is easy, but require a few more steps than just adding a regular library:

libraryDependencies +="org.ensime"%%"pcplod"%"1.2.1"%"test",
// WORKAROUND https://github.com/ensime/pcplod/issues/12
fork in Test:=true,
javaOptions in Test++=Seq(
s"""-Dpcplod.settings=${(scalacOptions in Test).value.filterNot(_.contains(",")).mkString(",")}""",
s"""-Dpcplod.classpath=${(fullClasspath in Test).value.map(_.data).mkString(",")}"""
)

The dependencyOverrides feature of SBT is recommended to ensure that the correct version of the scala compiler is used

dependencyOverrides +="org.scala-lang"%"scala-compiler"% scalaVersion.value

If you are testing a compiler plugin you may already be aware that you must add something like the following to your test configuration

scalacOptions in Test++= {
valjar= (packageBin in Compile).value
Seq(s"-Xplugin:${jar.getAbsolutePath}", s"-Jdummy=${jar.lastModified}") // ensures recompile
}

How to use it

PC Plod uses the loan pattern to let you write tests in whatever testing framework you want.

Loading Scala Sources

Since you're simulating a scala developer who is using your macro / plugin to write scala code, you put the code that you want to test into the test/resources folder of your project (not test/scala). Add source resources as needed

importorg.ensime.pcplod._

withPcPlod { pc =>
pc.loadScala("path/to/package/foo.scala")
// your tests here
pc.loadScala("path/to/package/bar.scala")
pc.unloadScala("path/to/package/foo.scala")
// more tests here
}

there is also a simplified variant (Mr Plod) which only supports one source (a simpler assertion API)

withMrPlod("path/to/package/foo.scala") { mr =>// your tests here
}

Making Assertions

The PcPlod instance has the following main assertions:

• symbolAtPoint(res: String, p: Point): Option[String] - the name of the symbol at point.
• typeAtPoint(res: String, p: Point): Option[String] - the return type of the symbol at the point.
• messages: List[PcMessage]

Typically if symbolAtPoint or typeAtPoint do not work (or there are any errors) then your code is not expected to work in the presentation compiler.

A variant of typeAtPoint and symbolAtPoint without the res is provided for withMrPlod.

An implicit conversion for Point means that any of the following can be provided in its place:

• Int the number of characters
• (Int, Int) the line and column
• Symbol corresponding to noddy syntax

with all counting from zero.

Noddy Syntax

Instead of having to manually count the location in the source, you can augment your test sources with a @noddy_syntax@ that will be stripped and treated as meta data when loaded:

objectF@foo@oo {
defbar(a@input_a@:String):Int=???
}

in this case, the symbol 'foo will refer to the letter F of Foo and the symbol 'input_a will refer to the parameter a of bar (i.e. the character immediately before the marker). Noddy names can only be alphanumeric or underscore.