feat: add KtlintModule object

build.mill

@@ -208,6 +208,7 @@ object Deps {
     val koverCli = ivy"org.jetbrains.kotlinx:kover-cli:$koverVersion"
     val koverJvmAgent = ivy"org.jetbrains.kotlinx:kover-jvm-agent:$koverVersion"
     val ktfmt = ivy"com.facebook:ktfmt:0.52"
+    val ktlint = ivy"com.pinterest.ktlint:ktlint-core:0.49.1"
     val sbtTestInterface = ivy"com.github.sbt:junit-interface:0.13.2"
 
     def all = Seq(
@@ -222,6 +223,7 @@ object Deps {
       koverCli,
       koverJvmAgent,
       ktfmt,
+      ktlint,
       sbtTestInterface,
     )
   }

example/kotlinlib/linting/2-ktlint/build.mill

@@ -27,4 +27,7 @@ error: ...src/example/FooWrong.kt:6:28: Missing newline before ")" (standard:par
 > ./mill ktlint --format true
 
 > ./mill ktlint # after fixing the violations, ktlint no longer errors
+
+> ./mill mill.kotlinlib.ktlint.KtlintModule/ # alternatively, use external module to check/format
+
 */

kotlinlib/package.mill

@@ -18,6 +18,7 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
     BuildInfo.Value("kotlinVersion", build.Deps.kotlinVersion, "Version of Kotlin"),
     BuildInfo.Value("koverVersion", build.Deps.RuntimeDeps.koverVersion, "Version of Kover."),
     BuildInfo.Value("ktfmtVersion", build.Deps.RuntimeDeps.ktfmt.version, "Version of Ktfmt."),
+    BuildInfo.Value("ktlintVersion", build.Deps.RuntimeDeps.ktlint.version, "Version of ktlint."),
     BuildInfo.Value("detektVersion", build.Deps.RuntimeDeps.detektCli.version, "Version of Detekt."),
     BuildInfo.Value("dokkaVersion", build.Deps.RuntimeDeps.dokkaVersion, "Version of Dokka."),
     BuildInfo.Value("kotlinxHtmlJvmDep", Dep.unparse(build.Deps.RuntimeDeps.kotlinxHtmlJvm).get, "kotlinx-html-jvm dependency (used for Dokka)"),

kotlinlib/src/mill/kotlinlib/ktlint/KtlintModule.scala

@@ -2,54 +2,21 @@ package mill.kotlinlib.ktlint
 
 import mill._
 import mill.api.{Loose, PathRef}
-import mill.kotlinlib.{DepSyntax, KotlinModule}
+import mill.define.{Discover, ExternalModule}
+import mill.javalib.JavaModule
+import mill.kotlinlib.DepSyntax
 import mill.util.Jvm
 
 /**
  * Performs formatting checks on Kotlin source files using [[https://pinterest.github.io/ktlint/latest/install/integrations/ Ktlint]].
  */
-trait KtlintModule extends KotlinModule {
+trait KtlintModule extends JavaModule {
 
   /**
    * Runs [[https://pinterest.github.io/ktlint/latest/install/integrations/ Ktlint]]
    */
-  def ktlint(@mainargs.arg ktlintArgs: KtlintArgs): Command[Unit] = T.command {
-    val exitCode = ktlint0(ktlintArgs.format)()
-
-    ktlintHandleErrors(ktlintArgs.check, exitCode)
-  }
-
-  private def ktlint0(format: Boolean) = T.task {
-
-    T.log.info("running ktlint ...")
-
-    val configArgument = ktlintConfig() match {
-      case Some(path) => Seq("--editorconfig", path.path.toString())
-      case None => Seq.empty
-    }
-    val formatArgument = if (format) Seq("-F") else Seq.empty
-    val args = ktlintOptions() ++ configArgument ++ formatArgument
-
-    Jvm.callSubprocess(
-      mainClass = "com.pinterest.ktlint.Main",
-      classPath = ktlintClasspath().map(_.path),
-      mainArgs = args,
-      workingDir = millSourcePath, // allow passing relative paths for sources like src/a/b
-      streamOut = true,
-      check = false
-    ).exitCode
-  }
-
-  private def ktlintHandleErrors(check: Boolean, exitCode: Int)(implicit ctx: mill.api.Ctx) = {
-
-    if (exitCode == 0) {} // do nothing
-    else {
-      if (check) {
-        throw new RuntimeException(s"ktlint exited abnormally with exit code = $exitCode")
-      } else {
-        T.log.error(s"ktlint exited abnormally with exit code = $exitCode")
-      }
-    }
+  def ktlint(@mainargs.arg ktlintArgs: KtlintArgs): Command[Unit] = Task.Command {
+    KtlintModule.ktlintAction(ktlintArgs, ktlintConfig(), ktlintOptions(), ktlintClasspath())
   }
 
   /**
@@ -82,3 +49,85 @@ trait KtlintModule extends KotlinModule {
     Seq.empty[String]
   }
 }
+
+object KtlintModule extends ExternalModule with KtlintModule with TaskModule {
+  override def defaultCommandName(): String = "reformatAll"
+
+  lazy val millDiscover: Discover = Discover[this.type]
+
+  /**
+   * Reformats Kotlin source files.
+   *
+   * @param check if an exception should be raised when formatting errors are found
+   *              - when set, files are not formatted
+   */
+  def reformatAll(
+      check: mainargs.Flag = mainargs.Flag(value = false)
+  ): Command[Unit] = Task.Command {
+    ktlintAction(
+      KtlintArgs(format = true, check = check.value),
+      ktlintConfig(),
+      ktlintOptions(),
+      ktlintClasspath()
+    )
+  }
+
+  /**
+   * Checks the Kotlin source files formatting without reformatting the files.
+   *
+   * @param check if an exception should be raised when formatting errors are found
+   *              - when set, files are not formatted
+   */
+  def checkFormatAll(
+      check: mainargs.Flag = mainargs.Flag(value = false)
+  ): Command[Unit] = Task.Command {
+    ktlintAction(
+      KtlintArgs(format = false, check = check.value),
+      ktlintConfig(),
+      ktlintOptions(),
+      ktlintClasspath()
+    )
+  }
+
+  private def ktlintAction(
+      ktlintArgs: KtlintArgs,
+      config: Option[PathRef],
+      options: Seq[String],
+      classPath: Loose.Agg[PathRef]
+  )(implicit ctx: api.Ctx): Unit = {
+    if (ktlintArgs.check) {
+      ctx.log.info("checking format in kotlin sources ...")
+    } else {
+      ctx.log.info("formatting kotlin sources ...")
+    }
+
+    val configArgument = config match {
+      case Some(path) => Seq("--editorconfig", path.path.toString())
+      case None => Seq.empty
+    }
+    val formatArgument = if (ktlintArgs.format) Seq("--format") else Seq.empty
+
+    val args = Seq.newBuilder[String]
+    args ++= options
+    args ++= configArgument
+    args ++= formatArgument
+
+    val exitCode = Jvm.callSubprocess(
+      mainClass = "com.pinterest.ktlint.Main",
+      classPath = classPath.map(_.path),
+      mainArgs = args.result(),
+      workingDir = millSourcePath, // allow passing relative paths for sources like src/a/b
+      streamOut = true,
+      check = false
+    ).exitCode
+
+    if (exitCode == 0) {} // do nothing
+    else {
+      if (ktlintArgs.check) {
+        throw new RuntimeException(s"ktlint exited abnormally with exit code = $exitCode")
+      } else {
+        ctx.log.error(s"ktlint exited abnormally with exit code = $exitCode")
+      }
+    }
+  }
+}