Verify compilation during build

.github/workflows/ci.yml

@@ -49,6 +49,11 @@ jobs:
         sudo apt-get update
         sudo apt-get install libidn2-dev libcurl3-dev
         echo "STTP_NATIVE=1" >> $GITHUB_ENV
+    - name: Install scala-cli
+      if: matrix.target-platform == 'JVM' && matrix.java == '21' && matrix.scala-version == '3'
+      uses: VirtusLab/scala-cli-setup@main
+      with:
+        jvm: '' # needed because scala-cli-setup otherwise forces the installation of their default JVM (17)        
     - name: Enable Loom-specific modules
       if: matrix.java == '21'
       run: echo "ONLY_LOOM=1" >> $GITHUB_ENV
@@ -57,6 +62,9 @@ jobs:
     - name: Compile documentation
       if: matrix.target-platform == 'JVM' && matrix.java == '11'
       run: sbt -v compileDocs
+    - name: Verify that examples compile using Scala CLI
+      if: matrix.target-platform == 'JVM' && matrix.java == '21' && matrix.scala-version == '3'
+      run: sbt $SBT_JAVA_OPTS -v "project examples3" verifyExamplesCompileUsingScalaCli      
     - name: Test
       run: sbt -v "testScoped ${{ matrix.scala-version }} ${{ matrix.target-platform }}"        
     - name: Prepare release notes

build.sbt

@@ -21,6 +21,7 @@ val ideScalaVersion = scala3
 
 lazy val testServerPort = settingKey[Int]("Port to run the http test server on")
 lazy val startTestServer = taskKey[Unit]("Start a http server used by tests")
+lazy val verifyExamplesCompileUsingScalaCli = taskKey[Unit]("Verify that each example compiles using Scala CLI")
 
 // slow down for CI
 parallelExecution in Global := false
@@ -967,7 +968,8 @@ lazy val examples = (projectMatrix in file("examples"))
       "org.json4s" %% "json4s-native" % json4sVersion,
       pekkoStreams,
       logback
-    )
+    ),
+    verifyExamplesCompileUsingScalaCli := VerifyExamplesCompileUsingScalaCli(sLog.value, sourceDirectory.value)
   )
   .jvmPlatform(scalaVersions = List(examplesScalaVersion))
   .dependsOn(

project/FileUtils.scala

@@ -0,0 +1,22 @@
+import java.io.File
+import java.nio.file.{FileVisitResult, Files, Path, SimpleFileVisitor}
+import java.nio.file.attribute.BasicFileAttributes
+
+object FileUtils {
+  def listScalaFiles(basePath: File): Seq[Path] = {
+    val dirPath = basePath.toPath
+    var result = Vector.empty[Path]
+
+    val fileVisitor = new SimpleFileVisitor[Path] {
+      override def visitFile(file: Path, attrs: BasicFileAttributes): FileVisitResult = {
+        if (file.toString.endsWith(".scala")) {
+          result = result :+ file
+        }
+        FileVisitResult.CONTINUE
+      }
+    }
+
+    Files.walkFileTree(dirPath, fileVisitor)
+    result
+  }
+}

project/VerifyExamplesCompileUsingScalaCli.scala

@@ -0,0 +1,24 @@
+import java.io.File
+import sbt.Logger
+import scala.sys.process.{Process, ProcessLogger}
+
+object VerifyExamplesCompileUsingScalaCli {
+  def apply(log: Logger, examplesSrcPath: File): Unit = {
+    val examples = FileUtils.listScalaFiles(examplesSrcPath)
+    log.info(s"Found ${examples.size} examples")
+
+    for (example <- examples) {
+      log.info(s"Compiling: $example")
+      val errorOutput = new StringBuilder
+      val logger = ProcessLogger((o: String) => (), (e: String) => errorOutput.append(e + "\n"))
+      try {
+        val result = Process(List("scala-cli", "compile", example.toFile.getAbsolutePath), examplesSrcPath).!(logger)
+        if (result != 0) {
+          throw new Exception(s"""Compiling $example failed.\n$errorOutput""".stripMargin)
+        }
+      } finally {
+        Process(List("scala-cli", "clean", example.toFile.getAbsolutePath), examplesSrcPath).!
+      }
+    }
+  }
+}