Add Ktfmt support (#3620)

Fixes #3612.

This PR is based on the logic done in #3531, so it looks quite similar.

Co-authored-by: 0xnm <[email protected]>

example/kotlinlib/linting/3-ktfmt/build.mill

@@ -0,0 +1,25 @@
+package build
+
+import mill._
+import mill.util.Jvm
+import mill.api.Loose
+import kotlinlib.KotlinModule
+import kotlinlib.contrib.ktfmt.KtfmtModule
+
+object `package` extends RootModule with KotlinModule with KtfmtModule {
+
+  def kotlinVersion = "1.9.24"
+
+}
+
+/** Usage
+
+> ./mill ktfmt --format=false # run ktfmt to produce a list of files which should be formatter
+...src/example/FooWrong.kt...
+> ./mill ktfmt # running without arguments will format all files
+Done formatting ...src/example/FooWrong.kt
+> ./mill ktfmt # after fixing the violations, ktfmt no longer prints any file
+
+> ./mill mill.kotlinlib.contrib.ktfmt.KtfmtModule/ __.sources   # alternatively, use external module to check/format
+
+*/

example/kotlinlib/linting/3-ktfmt/src/example/FooRight.kt

@@ -0,0 +1,11 @@
+package example
+
+class FooRight {
+    fun someFun(one: String, two: String) = Unit
+
+    companion object {
+        const val LINE =
+            "veryyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy" +
+                "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyylongline"
+    }
+}

example/kotlinlib/linting/3-ktfmt/src/example/FooWrong.kt

@@ -0,0 +1,12 @@
+package example
+
+class FooWrong {
+
+         fun someFun(one: String, two: String) = Unit
+
+    companion object {
+        const val LINE =
+            "veryyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy" +
+                "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyylongline"
+    }
+}

kotlinlib/src/mill/kotlinlib/contrib/ktfmt/KtfmtArgs.scala

@@ -0,0 +1,22 @@
+package mill.kotlinlib.contrib.ktfmt
+
+import mainargs.{ParserForClass, main}
+
+/**
+ * Arguments for [[KtfmtModule.ktfmt]].
+ *
+ * @param style               formatting style to apply, can be either "kotlin", "meta" or "google". Default is "kotlin".
+ * @param format              if auto-formatting should be done. Default is "true"
+ * @param removeUnusedImports flag to remove unused imports if auto-formatting is applied. Default is "true".
+ */
+@main(doc = "arguments for KtfmtModule.ktfmt")
+case class KtfmtArgs(
+    style: String = "kotlin",
+    format: Boolean = true,
+    removeUnusedImports: Boolean = true
+)
+
+object KtfmtArgs {
+
+  implicit val PFC: ParserForClass[KtfmtArgs] = ParserForClass[KtfmtArgs]
+}

kotlinlib/src/mill/kotlinlib/contrib/ktfmt/KtfmtModule.scala

@@ -0,0 +1,139 @@
+package mill
+package kotlinlib.contrib.ktfmt
+
+import mainargs.Leftover
+import mill.api.{Loose, PathRef}
+import mill.define.{Discover, ExternalModule}
+import mill.kotlinlib.{DepSyntax, KotlinModule}
+import mill.main.Tasks
+import mill.util.Jvm
+
+trait KtfmtBaseModule extends KotlinModule {
+
+  /**
+   * Classpath for running Ktfmt.
+   */
+  def ktfmtClasspath: T[Loose.Agg[PathRef]] = T {
+    defaultResolver().resolveDeps(
+      Agg(ivy"com.facebook:ktfmt:${ktfmtVersion()}")
+    )
+  }
+
+  /**
+   * Ktfmt version.
+   */
+  def ktfmtVersion: T[String] = T {
+    "0.52"
+  }
+
+  /**
+   * Additional arguments for Ktfmt. Check
+   * [[https://github.com/facebook/ktfmt/blob/main/core/src/main/java/com/facebook/ktfmt/cli/ParsedArgs.kt#L51 available options]].
+   */
+  def ktfmtOptions: T[Seq[String]] = T {
+    Seq.empty[String]
+  }
+}
+
+/**
+ * Performs formatting checks on Kotlin source files using [[https://github.com/facebook/ktfmt Ktfmt]].
+ */
+trait KtfmtModule extends KtfmtBaseModule {
+
+  /**
+   * Runs [[https://github.com/facebook/ktfmt Ktfmt]]
+   *
+   * @param ktfmtArgs arguments for the [[https://github.com/facebook/ktfmt Ktfmt]].
+   * @param sources list of sources to run  the tool on. If not provided, default module sources will be taken.
+   */
+  def ktfmt(
+      @mainargs.arg ktfmtArgs: KtfmtArgs,
+      @mainargs.arg(positional = true) sources: Leftover[String]
+  ): Command[Unit] = Task.Command {
+    val _sources = if (sources.value.isEmpty) {
+      this.sources()
+    } else {
+      sources.value.iterator.map(rel => PathRef(millSourcePath / os.RelPath(rel)))
+    }
+    KtfmtModule.ktfmtAction(
+      ktfmtArgs.style,
+      ktfmtArgs.format,
+      ktfmtArgs.removeUnusedImports,
+      _sources,
+      ktfmtClasspath(),
+      ktfmtOptions()
+    )
+  }
+}
+
+object KtfmtModule extends ExternalModule with KtfmtBaseModule with TaskModule {
+
+  def kotlinVersion = "1.9.24"
+
+  lazy val millDiscover: Discover = Discover[this.type]
+
+  override def defaultCommandName(): String = "formatAll"
+
+  /**
+   * Runs [[https://github.com/facebook/ktfmt Ktfmt]].
+   *
+   * @param ktfmtArgs formatting arguments
+   * @param sources list of [[KotlinModule]] to process
+   */
+  def formatAll(
+      @mainargs.arg ktfmtArgs: KtfmtArgs,
+      @mainargs.arg(positional = true) sources: Tasks[Seq[PathRef]]
+  ): Command[Unit] = Task.Command {
+    val _sources = T.sequence(sources.value)().iterator.flatten
+    ktfmtAction(
+      ktfmtArgs.style,
+      ktfmtArgs.format,
+      ktfmtArgs.removeUnusedImports,
+      _sources,
+      ktfmtClasspath(),
+      ktfmtOptions()
+    )
+  }
+
+  private def ktfmtAction(
+      style: String,
+      format: Boolean,
+      removeUnusedImports: Boolean,
+      sources: IterableOnce[PathRef],
+      classPath: Loose.Agg[PathRef],
+      options: Seq[String]
+  )(implicit ctx: api.Ctx): Unit = {
+
+    ctx.log.info("running ktfmt ...")
+
+    val args = Seq.newBuilder[String]
+    args ++= options
+    args += (style match {
+      case "kotlin" => "--kotlinlang-style"
+      case "google" => "--google-style"
+      case "meta" => "--meta-style"
+      case _ => throw new IllegalArgumentException(s"Unknown style ktfmt style: $style")
+    })
+    if (!format) {
+      args += "--dry-run"
+    }
+    if (!removeUnusedImports) {
+      args += "--do-not-remove-unused-imports"
+    }
+    args ++= sources.iterator.map(_.path.toString())
+
+    val exitCode = Jvm.callSubprocess(
+      mainClass = "com.facebook.ktfmt.cli.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 {
+      throw new RuntimeException(s"ktfmt exited abnormally with exit code = $exitCode")
+    }
+  }
+}

kotlinlib/test/resources/contrib/ktfmt/after/imports/Example.kt

@@ -0,0 +1,7 @@
+import java.lang.RuntimeException
+
+class Example {
+    fun sample(arg: String) {
+        println(arg)
+    }
+}

kotlinlib/test/resources/contrib/ktfmt/after/style/google/Example.kt

@@ -0,0 +1,5 @@
+class Example {
+  fun sample(arg: String) {
+    println(arg)
+  }
+}

kotlinlib/test/resources/contrib/ktfmt/after/style/kotlin/Example.kt

@@ -0,0 +1,5 @@
+class Example {
+    fun sample(arg: String) {
+        println(arg)
+    }
+}

kotlinlib/test/resources/contrib/ktfmt/after/style/meta/Example.kt

@@ -0,0 +1,5 @@
+class Example {
+  fun sample(arg: String) {
+    println(arg)
+  }
+}

kotlinlib/test/resources/contrib/ktfmt/before/src/Example.kt

@@ -0,0 +1,5 @@
+import java.lang.RuntimeException
+
+class Example {
+                      fun sample(arg: String) {println(arg)}
+}

kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala

@@ -0,0 +1,150 @@
+package mill.kotlinlib.contrib.ktfmt
+
+import mainargs.Leftover
+import mill.{T, api}
+import mill.kotlinlib.KotlinModule
+import mill.main.Tasks
+import mill.testkit.{TestBaseModule, UnitTester}
+import utest.{TestSuite, Tests, assert, test}
+
+object KtfmtModuleTests extends TestSuite {
+  def tests: Tests = Tests {
+
+    val (before, after) = {
+      val root = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "contrib" / "ktfmt"
+      (root / "before", root / "after")
+    }
+
+    test("ktfmt - kotlin style") {
+      assert(
+        checkState(
+          afterFormat(before, style = "kotlin"),
+          after / "style" / "kotlin"
+        )
+      )
+    }
+
+    test("ktfmt - google style") {
+      assert(
+        checkState(
+          afterFormat(before, style = "google"),
+          after / "style" / "google"
+        )
+      )
+    }
+
+    test("ktfmt - meta style") {
+      assert(
+        checkState(
+          afterFormat(before, style = "meta"),
+          after / "style" / "meta"
+        )
+      )
+    }
+
+    test("ktfmt - dry-run") {
+      checkState(
+        afterFormat(before, format = true),
+        before
+      )
+    }
+
+    test("ktfmt - don't remove unused imports") {
+      checkState(
+        afterFormat(before, removeUnusedImports = false),
+        after / "imports"
+      )
+    }
+
+    test("ktfmt - explicit files") {
+      checkState(
+        afterFormat(before, sources = Seq("src/Example.kt")),
+        after / "style" / "kotlin"
+      )
+    }
+
+    test("formatAll") {
+
+      assert(
+        checkState(
+          afterFormatAll(before),
+          after / "style" / "kotlin"
+        )
+      )
+    }
+  }
+
+  def checkState(actualFiles: Seq[os.Path], expectedRoot: os.Path): Boolean = {
+    val expectedFiles = walkFiles(expectedRoot)
+    actualFiles.length == expectedFiles.length &&
+    actualFiles.iterator.zip(expectedFiles.iterator).forall {
+      case (actualFile, expectedFile) =>
+        val actual = os.read(actualFile)
+        val expected = os.read(expectedFile)
+        actual == expected
+    }
+  }
+
+  def afterFormat(
+      moduleRoot: os.Path,
+      style: String = "kotlin",
+      format: Boolean = true,
+      removeUnusedImports: Boolean = true,
+      sources: Seq[String] = Seq.empty
+  ): Seq[os.Path] = {
+
+    object module extends TestBaseModule with KotlinModule with KtfmtModule {
+      override def kotlinVersion: T[String] = "1.9.24"
+    }
+
+    val eval = UnitTester(module, moduleRoot)
+
+    eval(module.ktfmt(
+      KtfmtArgs(
+        style = style,
+        format = format,
+        removeUnusedImports = removeUnusedImports
+      ),
+      sources = Leftover(sources: _*)
+    )).fold(
+      {
+        case api.Result.Exception(cause, _) => throw cause
+        case failure => throw failure
+      },
+      { _ =>
+        val Right(sources) = eval(module.sources)
+
+        sources.value.flatMap(ref => walkFiles(ref.path))
+      }
+    )
+  }
+
+  def afterFormatAll(modulesRoot: os.Path, format: Boolean = true): Seq[os.Path] = {
+
+    object module extends TestBaseModule with KotlinModule {
+      override def kotlinVersion: T[String] = "1.9.24"
+    }
+
+    val eval = UnitTester(module, modulesRoot)
+    eval(KtfmtModule.formatAll(
+      KtfmtArgs(
+        style = "kotlin",
+        format = format,
+        removeUnusedImports = true
+      ),
+      sources = Tasks(Seq(module.sources))
+    )).fold(
+      {
+        case api.Result.Exception(cause, _) => throw cause
+        case failure => throw failure
+      },
+      { _ =>
+        val Right(sources) = eval(module.sources)
+        sources.value.flatMap(ref => walkFiles(ref.path))
+      }
+    )
+  }
+
+  def walkFiles(root: os.Path): Seq[os.Path] =
+    os.walk(root).filter(os.isFile)
+}