First pass at using a compiler plugin to remove the need for the `override` keyword when overriding a field within a `mill.Module`

This only applies to `mill.Module`s, not overrides elsewhere which still require the keyword. `mill.Module`s tend to have lots and lots of overriding, so the keyword is basically noise.

Also includes the necessary build changes to enable the locally-built Scalac plugin when compiling the test suite. Note that no changes are necessary for the executable assembly, because the `scalac-plugin.xml` will be included in the assembly and get picked up by the Ammonite scalac plugin classloader automatically

1 files changed, 30 insertions, 15 deletions

diff --git a/build.sc b/build.sc
index a7508941..04bc489b 100755
--- a/build.sc
+++ b/build.sc
@@ -3,32 +3,46 @@ import mill._
 import mill.scalaplugin._
 import mill.modules.Jvm.createAssembly
 
+
+object CompilerPlugin extends SbtScalaModule{
+  def scalaVersion = "2.12.4"
+  def basePath = pwd / 'plugin
+  def ivyDeps = Seq(
+    Dep.Java("org.scala-lang", "scala-compiler", scalaVersion()),
+    Dep("com.lihaoyi", "sourcecode", "0.1.4")
+  )
+}
+
 trait MillModule extends SbtScalaModule{ outer =>
   def scalaVersion = "2.12.4"
 
-  override def compileIvyDeps = Seq(Dep("com.lihaoyi", "acyclic", "0.1.7"))
-  override def scalacOptions = Seq("-P:acyclic:force")
-  override def scalacPluginIvyDeps = Seq(Dep("com.lihaoyi", "acyclic", "0.1.7"))
+  def compileIvyDeps = Seq(Dep("com.lihaoyi", "acyclic", "0.1.7"))
+  def scalacOptions = Seq("-P:acyclic:force")
+  def scalacPluginIvyDeps = Seq(Dep("com.lihaoyi", "acyclic", "0.1.7"))
 
   def testArgs = T{ Seq.empty[String] }
 
   object test extends this.Tests{
-    override def defaultCommandName() = "forkTest"
-    override def forkArgs = T{ testArgs() }
-    override def projectDeps =
+    def defaultCommandName() = "forkTest"
+    def forkArgs = T{ testArgs() }
+    def projectDeps =
       if (this == Core.test) Seq(Core)
       else Seq(outer, Core.test)
-    override def ivyDeps = Seq(Dep("com.lihaoyi", "utest", "0.6.0"))
+    def ivyDeps = Seq(Dep("com.lihaoyi", "utest", "0.6.0"))
     def testFramework = "mill.UTestFramework"
+    def scalacPluginClasspath = super.scalacPluginClasspath() ++ Seq(CompilerPlugin.jar())
+
   }
 }
 
 object Core extends MillModule {
-  override def compileIvyDeps = Seq(
+  def projectDeps = Seq(CompilerPlugin)
+
+  def compileIvyDeps = Seq(
     Dep.Java("org.scala-lang", "scala-reflect", scalaVersion())
   )
 
-  override def ivyDeps = Seq(
+  def ivyDeps = Seq(
     Dep("com.lihaoyi", "sourcecode", "0.1.4"),
     Dep("com.lihaoyi", "pprint", "0.5.3"),
     Dep.Point("com.lihaoyi", "ammonite", "1.0.3"),
@@ -61,7 +75,7 @@ val bridges = for{
 } yield new ScalaModule{
   def basePath = pwd / 'bridge
   def scalaVersion = crossVersion
-  override def allSources = T{
+  def allSources = T{
 
     val v = crossVersion.split('.').dropRight(1).mkString(".")
     val url =
@@ -77,7 +91,7 @@ val bridges = for{
 
     Seq(PathRef(curlDest / 'classes))
   }
-  override def ivyDeps = Seq(
+  def ivyDeps = Seq(
     Dep.Java("org.scala-lang", "scala-compiler", crossVersion),
     Dep.Java("org.scala-sbt", "compiler-interface", "1.0.5")
   )
@@ -85,16 +99,17 @@ val bridges = for{
 
 object ScalaPlugin extends MillModule {
 
-  override def projectDeps = Seq(Core)
+  def projectDeps = Seq(Core)
   def basePath = pwd / 'scalaplugin
 
-  override def testArgs = T{
+  def testArgs = T{
     val mapping = Map(
       "MILL_COMPILER_BRIDGE_2_10_6"  -> bridges("2.10.6").compile().classes.path,
       "MILL_COMPILER_BRIDGE_2_11_8"  -> bridges("2.11.8").compile().classes.path,
       "MILL_COMPILER_BRIDGE_2_11_11" -> bridges("2.11.11").compile().classes.path,
       "MILL_COMPILER_BRIDGE_2_12_3"  -> bridges("2.12.3").compile().classes.path,
       "MILL_COMPILER_BRIDGE_2_12_4"  -> bridges("2.12.4").compile().classes.path,
+      "MILL_COMPILER_PLUGIN" -> CompilerPlugin.compile().classes.path
     )
     for((k, v) <- mapping.toSeq) yield s"-D$k=$v"
   }
@@ -103,7 +118,7 @@ object ScalaPlugin extends MillModule {
 
 object Bin extends MillModule {
 
-  override def projectDeps = Seq(ScalaPlugin)
+  def projectDeps = Seq(ScalaPlugin)
   def basePath = pwd / 'bin
 
   def releaseAssembly = T{
@@ -116,7 +131,7 @@ object Bin extends MillModule {
     )
   }
 
-  override def prependShellScript =
+  def prependShellScript =
     "#!/usr/bin/env sh\n" +
     s"""exec java ${ScalaPlugin.testArgs().mkString(" ")} $$JAVA_OPTS -cp "$$0" mill.Main "$$@" """