Fix formatting and add a CI job

.github/workflows/ci.yml

@@ -11,6 +11,20 @@ permissions:
   contents: read
 
 jobs:
+  format:
+    timeout-minutes: 15
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+          submodules: true
+      - uses: coursier/cache-action@v8
+        with:
+          ignoreJob: true
+      - uses: VirtusLab/scala-cli-setup@v1
+      - run: scala-cli fmt . --check
+
   build:
     runs-on: ubuntu-latest
     steps:

.gitignore

@@ -4,3 +4,10 @@ target/
 project/.boot/
 project/.ivy/
 project/.sbtboot/
+
+.idea/
+.metals/
+.vscode/
+.bsp/
+.bloop/
+.cursor/

agent/src/main/scala/sloth/agent/AgentConfig.scala

@@ -34,13 +34,11 @@ object AgentConfig {
 
   /** Parse agent config from the agentArgs string.
     *
-    * Format: comma-separated options, e.g.:
-    *   "verbose,include=com.example.,exclude=com.example.internal."
+    * Format: comma-separated options, e.g.: "verbose,include=com.example.,exclude=com.example.internal."
     *
     * Log level options (each sets the scribe log level):
     *   - verbose: Debug level
-    *   - trace: Trace level
-    *   (default is Warn if none specified)
+    *   - trace: Trace level (default is Warn if none specified)
     */
   def parse(agentArgs: String): AgentConfig = {
     if (agentArgs == null || agentArgs.trim.isEmpty) return AgentConfig()

agent/src/main/scala/sloth/agent/SlothAgent.scala

@@ -4,8 +4,8 @@ import java.lang.instrument.Instrumentation
 
 /** Java agent entry point for Sloth.
   *
-  * Patches Scala 3.0-3.7 lazy val bytecode at class-load time to use
-  * VarHandle-based implementation (3.8+ format), avoiding sun.misc.Unsafe.
+  * Patches Scala 3.0-3.7 lazy val bytecode at class-load time to use VarHandle-based implementation (3.8+ format),
+  * avoiding sun.misc.Unsafe.
   *
   * Usage: java -javaagent:sloth-agent.jar[=options] -jar app.jar
   *

agent/src/main/scala/sloth/agent/SlothTransformer.scala

@@ -9,27 +9,29 @@ import sloth.patching.BytecodePatcher
 
 /** ClassFileTransformer that patches Scala 3.0-3.7 lazy val bytecode at load time.
   *
-  * Uses the group-based patching API to correctly handle companion pairs where
-  * lazy val implementation is split across object and class files. When one side
-  * of a companion pair is loaded, the other side is read via getResourceAsStream
-  * (pure I/O, no class loading) and both are patched together. The companion's
-  * patched bytes are buffered for when it actually loads.
+  * Uses the group-based patching API to correctly handle companion pairs where lazy val implementation is split across
+  * object and class files. When one side of a companion pair is loaded, the other side is read via getResourceAsStream
+  * (pure I/O, no class loading) and both are patched together. The companion's patched bytes are buffered for when it
+  * actually loads.
   */
 class SlothTransformer(config: AgentConfig) extends ClassFileTransformer {
 
-  /** Packages to always skip (JDK internals, our own code, Scala runtime).
-    * NOTE: String literals for our own package and scala/runtime/ are constructed
-    * via StringBuilder/Array to prevent sbt-assembly shade rules from rewriting them.
-    * The agent receives UNSHADED class names from the JVM.
+  /** Packages to always skip (JDK internals, our own code, Scala runtime). NOTE: String literals for our own package
+    * and scala/runtime/ are constructed via StringBuilder/Array to prevent sbt-assembly shade rules from rewriting
+    * them. The agent receives UNSHADED class names from the JVM.
     */
   private val skipPrefixes = Array(
-    "java/", "javax/", "jdk/", "sun/", "com/sun/",
+    "java/",
+    "javax/",
+    "jdk/",
+    "sun/",
+    "com/sun/",
     new StringBuilder("sl").append("oth/").toString,
     new StringBuilder("sca").append("la/runtime/").toString
   )
 
-  /** Buffer for patched companion bytes. When one side of a companion pair is patched,
-    * the other side's bytes are stored here and consumed (via remove) when that class loads.
+  /** Buffer for patched companion bytes. When one side of a companion pair is patched, the other side's bytes are
+    * stored here and consumed (via remove) when that class loads.
     */
   private val patchedCompanionBuffer = new ConcurrentHashMap[String, Array[Byte]]()
 
@@ -115,7 +117,9 @@ class SlothTransformer(config: AgentConfig) extends ClassFileTransformer {
           null
 
         case Right(groups) =>
-          scribe.debug(s"  group() returned ${groups.size} group(s): ${groups.map(g => s"${g.getClass.getSimpleName}(${g.primaryName})").mkString(", ")}")
+          scribe.debug(
+            s"  group() returned ${groups.size} group(s): ${groups.map(g => s"${g.getClass.getSimpleName}(${g.primaryName})").mkString(", ")}"
+          )
 
           // There should be exactly one group (single or companion pair)
           groups.headOption.map(BytecodePatcher.patch(_, classLoader = Some(loader))) match {

build.sbt

@@ -1,16 +1,18 @@
-inThisBuild(List(
-  organization := "org.virtuslab",
-  homepage := Some(url("https://github.com/VirtusLab/sloth")),
-  licenses := List("Apache-2.0" -> url("http://www.apache.org/licenses/LICENSE-2.0")),
-  developers := List(
-    Developer(
-      "lbialy",
-      "Łukasz Biały",
-      "lbialy@virtuslab.com",
-      url("https://github.com/VirtusLab")
+inThisBuild(
+  List(
+    organization := "org.virtuslab",
+    homepage := Some(url("https://github.com/VirtusLab/sloth")),
+    licenses := List("Apache-2.0" -> url("http://www.apache.org/licenses/LICENSE-2.0")),
+    developers := List(
+      Developer(
+        "lbialy",
+        "Łukasz Biały",
+        "lbialy@virtuslab.com",
+        url("https://github.com/VirtusLab")
+      )
     )
   )
-))
+)
 
 lazy val core = project
   .in(file("core"))
@@ -52,7 +54,7 @@ lazy val testops = project
     assembly / assemblyJarName := "sloth-testops.jar",
     assembly / assemblyMergeStrategy := {
       case PathList("META-INF", xs @ _*) => MergeStrategy.discard
-      case x => MergeStrategy.first
+      case x                             => MergeStrategy.first
     }
   )
   .dependsOn(core)
@@ -107,7 +109,7 @@ lazy val cli = project
     assembly / assemblyJarName := "sloth.jar",
     assembly / assemblyMergeStrategy := {
       case PathList("META-INF", xs @ _*) => MergeStrategy.discard
-      case x => MergeStrategy.first
+      case x                             => MergeStrategy.first
     }
   )
   .dependsOn(core)
@@ -133,7 +135,7 @@ lazy val agent = project
       new RuleTransformer(new RewriteRule {
         override def transform(node: Node): Seq[Node] = node match {
           case e: Elem if e.label == "dependencies" => NodeSeq.Empty
-          case n => n
+          case n                                    => n
         }
       }).transform(node).head
     },
@@ -152,17 +154,20 @@ lazy val agent = project
       val fullCp = (cliJar +: depJars).map(_.getAbsolutePath).mkString(java.io.File.pathSeparator)
 
       val debugAssembly = sys.env.contains("DEBUG_AGENT_ASSEMBLY")
-      val processLogger: scala.sys.process.ProcessLogger = if (debugAssembly)
-        scala.sys.process.ProcessLogger(s => log.info(s), s => log.error(s))
-      else scala.sys.process.ProcessLogger(_ => (), _ => ())
+      val processLogger: scala.sys.process.ProcessLogger =
+        if (debugAssembly)
+          scala.sys.process.ProcessLogger(s => log.info(s), s => log.error(s))
+        else scala.sys.process.ProcessLogger(_ => (), _ => ())
 
       val processedFiles = depJars.map { depJar =>
         val dest = processedDir / depJar.getName
         IO.copyFile(depJar, dest)
         if (debugAssembly) log.info(s"Processing ${depJar.getName}...")
-        val exitCode = scala.sys.process.Process(
-          Seq("java", "-cp", fullCp, "sloth.cli.Main", dest.getAbsolutePath)
-        ).!(processLogger)
+        val exitCode = scala.sys.process
+          .Process(
+            Seq("java", "-cp", fullCp, "sloth.cli.Main", dest.getAbsolutePath)
+          )
+          .!(processLogger)
         if (exitCode != 0) {
           throw new MessageOnlyException(s"Failed to process ${depJar.getName} (exit code $exitCode)")
         }
@@ -182,8 +187,8 @@ lazy val agent = project
     assembly / assemblyJarName := "sloth-agent.jar",
     assembly / assemblyMergeStrategy := {
       case PathList("META-INF", "MANIFEST.MF") => MergeStrategy.discard
-      case PathList("META-INF", xs @ _*) => MergeStrategy.discard
-      case x => MergeStrategy.first
+      case PathList("META-INF", xs @ _*)       => MergeStrategy.discard
+      case x                                   => MergeStrategy.first
     },
     assembly / assemblyShadeRules := Seq(
       ShadeRule.rename("sloth.**" -> "sloth.shaded.agent.@0").inAll,

cli/src/main/scala/sloth/cli/Main.scala

@@ -160,7 +160,11 @@ object Main {
   }
 
   /** Processes a classfile group */
-  private def processGroup(group: ClassfileGroup, targetDir: os.Path, classLoader: ClassLoader): (String, PatchGroupResult) = {
+  private def processGroup(
+      group: ClassfileGroup,
+      targetDir: os.Path,
+      classLoader: ClassLoader
+  ): (String, PatchGroupResult) = {
     val groupName = group.primaryName
     print(fansi.Color.Cyan(s"Processing: $groupName ... "))
 

core/src/main/scala/sloth/classfile/ClassfileComparator.scala

@@ -249,7 +249,7 @@ object ClassfileComparator {
       bytes1: Option[Array[Byte]] = None,
       bytes2: Option[Array[Byte]] = None
   ): Seq[Difference] = compare(class1, class2, bytes1, bytes2) match {
-    case FullyIdentical        => Seq.empty
-    case Different(diffs)      => diffs
+    case FullyIdentical   => Seq.empty
+    case Different(diffs) => diffs
   }
 }

core/src/main/scala/sloth/classfile/ClassfileModels.scala

@@ -96,12 +96,10 @@ sealed trait ClassfileError {
 object ClassfileError {
 
   /** Error during ASM class reading. */
-  final case class ReadError(message: String, cause: Option[Throwable] = None)
-      extends ClassfileError
+  final case class ReadError(message: String, cause: Option[Throwable] = None) extends ClassfileError
 
   /** Error during bytecode dump generation. */
-  final case class DumpError(message: String, cause: Option[Throwable] = None)
-      extends ClassfileError
+  final case class DumpError(message: String, cause: Option[Throwable] = None) extends ClassfileError
 
   /** Invalid or corrupted classfile. */
   final case class InvalidClassfile(