Add scalaCompilerPlugins to Mill project export

modules/cli/src/main/scala/scala/cli/exportCmd/Mill.scala

@@ -46,6 +46,11 @@ final case class Mill(
       MillProject(scalaVersion = Some(sv))
   }
 
+  private def scalaCompilerPlugins(buildOptions: BuildOptions): MillProject =
+    MillProject(scalaCompilerPlugins =
+      buildOptions.scalaOptions.compilerPlugins.toSeq.map(_.value.render)
+    )
+
   private def scalacOptionsSettings(buildOptions: BuildOptions): MillProject =
     MillProject(scalacOptions = buildOptions.scalaOptions.scalacOptions.toSeq.map(_.value.value))
 
@@ -187,6 +192,7 @@ final case class Mill(
       sourcesSettings(sourcesMain, sourcesTest),
       scalaVersionSettings(optionsMain, sourcesMain),
       scalacOptionsSettings(optionsMain),
+      scalaCompilerPlugins(optionsMain),
       dependencySettings(optionsMain, optionsTest),
       repositorySettings(optionsMain),
       if (optionsMain.platform.value == Platform.JS) scalaJsSettings(optionsMain.scalaJsOptions)

modules/cli/src/main/scala/scala/cli/exportCmd/MillProject.scala

@@ -12,6 +12,7 @@ final case class MillProject(
   testDeps: Seq[String] = Nil,
   scalaVersion: Option[String] = None,
   scalacOptions: Seq[String] = Nil,
+  scalaCompilerPlugins: Seq[String] = Nil,
   scalaJsVersion: Option[String] = None,
   scalaNativeVersion: Option[String] = None,
   nameOpt: Option[String] = None,
@@ -87,6 +88,23 @@ final case class MillProject(
           ")" + nl
       }
 
+    val maybeScalaCompilerPlugins =
+      if (scalaCompilerPlugins.isEmpty) ""
+      else {
+        val depLen = scalaCompilerPlugins.length
+        "def scalacPluginIvyDeps = super.scalacPluginIvyDeps() ++ Seq(" + nl +
+          scalaCompilerPlugins
+            .iterator
+            .zipWithIndex
+            .map {
+              case (dep, idx) =>
+                val maybeComma = if (idx == depLen - 1) "" else ","
+                """  ivy"""" + dep + "\"" + maybeComma + nl
+            }
+            .mkString + nl +
+          ")" + nl
+      }
+
     val maybeMain = mainClass.fold("") { mc =>
       s"""def mainClass = Some("$mc")""" + nl
     }
@@ -101,6 +119,7 @@ final case class MillProject(
          |  $maybeScalacOptions
          |  $extraDecs
          |  ${maybeDeps(mainDeps)}
+         |  $maybeScalaCompilerPlugins
          |  $maybeMain
          |  ${extraDecls.map("  " + _ + nl).mkString}
          |

modules/integration/src/test/scala/scala/cli/integration/ExportMillTestDefinitions.scala

@@ -76,6 +76,19 @@ abstract class ExportMillTestDefinitions(val scalaVersionOpt: Option[String])
         val output = res.out.text(Charset.defaultCharset())
         expect(output.filterNot(_.isWhitespace) == "[\"-deprecation\"]")
       }
+      locally {
+        // scalacPluginIvyDeps
+        val res =
+          os.proc(
+            root / "mill-proj" / launcher,
+            "--disable-ticker",
+            "show",
+            s"$projectName.scalacPluginIvyDeps"
+          ).call(cwd = root / "mill-proj")
+        val output = res.out.text(Charset.defaultCharset())
+        expect(output.contains("com.olegpy"))
+        expect(output.contains("better-monadic-for"))
+      }
       locally {
         // test
         val res =

modules/integration/src/test/scala/scala/cli/integration/ExportTestProjects.scala

@@ -12,6 +12,7 @@ object ExportTestProjects {
            |//> using resourceDir "./input"
            |//> using lib "org.scala-lang::scala3-compiler:$scalaVersion"
            |//> using option "-deprecation"
+           |//> using plugins "com.olegpy::better-monadic-for:0.3.1"
            |
            |import scala.io.Source
            |
@@ -28,6 +29,7 @@ object ExportTestProjects {
         s"""//> using scala "$scalaVersion"
            |//> using resourceDir "./input"
            |//> using option "-deprecation"
+           |//> using plugins "com.olegpy::better-monadic-for:0.3.1"
            |
            |import scala.io.Source
            |