Add Kotest support for Kotlin/JS (#3723)

This PR brings [Kotest](https://github.com/kotest/kotest) test engine
support for Kotlin/JS target test execution.

Replaces #3710.

---------

Co-authored-by: Li Haoyi <haoyi.sg@gmail.com>

example/kotlinlib/web/3-hello-kotlinjs/build.mill

@@ -1,46 +1,47 @@
-// KotlinJS support on Mill is still Work In Progress (WIP). As of time of writing it
-// Node.js/Webpack test runners and reporting, etc.
+// Kotlin/JS support on Mill is still Work In Progress (WIP). As of time of writing it
+// supports Node.js, but lacks support of Browser, Webpack, test runners, reporting, etc.
 //
 // The example below demonstrates only the minimal compilation, running, and testing of
-// a single KotlinJS module using a single third-party dependency. For more details in
-// fully developing KotlinJS support, see the following ticket:
+// a single Kotlin/JS module using a single third-party dependency. For more details in
+// fully developing Kotlin/JS support, see the following ticket:
 //
 // * https://github.com/com-lihaoyi/mill/issues/3611
 
 package build
 import mill._, kotlinlib._, kotlinlib.js._
 
-object foo extends KotlinJSModule {
+object `package` extends RootModule with KotlinJSModule {
   def moduleKind = ModuleKind.ESModule
   def kotlinVersion = "1.9.25"
   def kotlinJSRunTarget = Some(RunTarget.Node)
   def ivyDeps = Agg(
     ivy"org.jetbrains.kotlinx:kotlinx-html-js:0.11.0",
   )
-  object test extends KotlinJSModule with KotlinJSKotlinXTests
+  object test extends KotlinJSModule with KotestTests
 }
 
 
 /** Usage
 
-> mill foo.run
-Compiling 1 Kotlin sources to .../out/foo/compile.dest/classes...
+> mill run
+Compiling 1 Kotlin sources to .../out/compile.dest/classes...
 <h1>Hello World</h1>
 stringifiedJsObject: ["hello","world","!"]
 
-> mill foo.test # Test is incorrect, `foo.test`` fails
-Compiling 1 Kotlin sources to .../out/foo/test/compile.dest/classes...
-Linking IR to .../out/foo/test/linkBinary.dest/binaries
-produce executable: .../out/foo/test/linkBinary.dest/binaries
+> mill test # Test is incorrect, `test` fails
+Compiling 1 Kotlin sources to .../out/test/compile.dest/classes...
+Linking IR to .../out/test/linkBinary.dest/binaries
+produce executable: .../out/test/linkBinary.dest/binaries
+...
+error: ...AssertionFailedError: expected:<"<h1>Hello World Wrong</h1>"> but was:<"<h1>Hello World</h1>...
 ...
-error: AssertionError: Expected <<h1>Hello World</h1>>, actual <<h1>Hello World Wrong</h1>>.
 
-> cat out/foo/test/linkBinary.dest/binaries/test.js # Generated javascript on disk
-...assertEquals_0(..., '<h1>Hello World Wrong<\/h1>');...
+> cat out/test/linkBinary.dest/binaries/test.js # Generated javascript on disk
+...shouldBe(..., '<h1>Hello World Wrong<\/h1>');...
 ...
 
-> sed -i.bak 's/Hello World Wrong/Hello World/g' foo/test/src/foo/HelloTests.kt
+> sed -i.bak 's/Hello World Wrong/Hello World/g' test/src/foo/HelloTests.kt
 
-> mill foo.test # passes after fixing test
+> mill test # passes after fixing test
 
 */

example/kotlinlib/web/3-hello-kotlinjs/foo/src/foo/Hello.kt → example/kotlinlib/web/3-hello-kotlinjs/src/foo/Hello.kt

@@ -12,5 +12,5 @@ fun main() {
 }
 
 fun hello(): String {
-    return createHTML().h1 { +"Hello World" }.toString()
-}
+    return createHTML(prettyPrint = false).h1 { text("Hello World") }.toString()
+}

example/kotlinlib/web/3-hello-kotlinjs/test/src/foo/HelloTests.kt

@@ -0,0 +1,11 @@
+package foo
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+
+class HelloTests: FunSpec({
+    test("hello") {
+        val result = hello()
+        result shouldBe "<h1>Hello World Wrong</h1>"
+    }
+})

kotlinlib/src/mill/kotlinlib/js/KotlinJSModule.scala

@@ -122,14 +122,17 @@ trait KotlinJSModule extends KotlinModule { outer =>
     }
 
     kotlinJSRunTarget() match {
-      case Some(RunTarget.Node) => Jvm.runSubprocess(
+      case Some(RunTarget.Node) => {
+        val testBinaryPath = (linkResult.path / s"${moduleName()}.${moduleKind.extension}")
+          .toIO.getAbsolutePath
+        Jvm.runSubprocess(
           commandArgs = Seq(
-            "node",
-            (linkResult.path / s"${moduleName()}.${moduleKind.extension}").toIO.getAbsolutePath
-          ) ++ args().value,
+            "node"
+          ) ++ args().value ++ Seq(testBinaryPath),
           envArgs = T.env,
           workingDir = T.dest
         )
+      }
       case Some(x) =>
         T.log.error(s"Run target $x is not supported")
       case None =>
@@ -379,16 +382,16 @@ trait KotlinJSModule extends KotlinModule { outer =>
 
   // these 2 exist to ignore values added to the display name in case of the cross-modules
   // we already have cross-modules in the paths, so we don't need them here
-  private def moduleName() = millModuleSegments.value
-    .filter(_.isInstanceOf[Segment.Label])
-    .map(_.asInstanceOf[Segment.Label])
-    .last
-    .value
+  private def fullModuleNameSegments() = {
+    millModuleSegments.value
+      .collect { case label: Segment.Label => label.value } match {
+      case Nil => Seq("root")
+      case segments => segments
+    }
+  }
 
-  private def fullModuleName() = millModuleSegments.value
-    .filter(_.isInstanceOf[Segment.Label])
-    .map(_.asInstanceOf[Segment.Label].value)
-    .mkString("-")
+  private def moduleName() = fullModuleNameSegments().last
+  private def fullModuleName() = fullModuleNameSegments().mkString("-")
 
   // **NOTE**: This logic may (and probably is) be incomplete
   private def isKotlinJsLibrary(path: os.Path)(implicit ctx: mill.api.Ctx): Boolean = {
@@ -417,8 +420,45 @@ trait KotlinJSModule extends KotlinModule { outer =>
 
   // region Tests module
 
+  /**
+   * Generic trait to run tests for Kotlin/JS which doesn't specify test
+   * framework. For the particular implementation see [[KotlinTestPackageTests]] or [[KotestTests]].
+   */
   trait KotlinJSTests extends KotlinTests with KotlinJSModule {
 
+    // region private
+
+    // TODO may be optimized if there is a single folder for all modules
+    // but may be problematic if modules use different NPM packages versions
+    private def nodeModulesDir = Task(persistent = true) {
+      PathRef(T.dest)
+    }
+
+    // NB: for the packages below it is important to use specific version
+    // otherwise with random versions there is a possibility to have conflict
+    // between the versions of the shared transitive deps
+    private def mochaModule = Task {
+      val workingDir = nodeModulesDir().path
+      Jvm.runSubprocess(
+        commandArgs = Seq("npm", "install", "mocha@10.2.0"),
+        envArgs = T.env,
+        workingDir = workingDir
+      )
+      PathRef(workingDir / "node_modules" / "mocha" / "bin" / "mocha.js")
+    }
+
+    private def sourceMapSupportModule = Task {
+      val workingDir = nodeModulesDir().path
+      Jvm.runSubprocess(
+        commandArgs = Seq("npm", "install", "source-map-support@0.5.21"),
+        envArgs = T.env,
+        workingDir = nodeModulesDir().path
+      )
+      PathRef(workingDir / "node_modules" / "source-map-support" / "register.js")
+    }
+
+    // endregion
+
     override def testFramework = ""
 
     override def kotlinJSBinaryKind: T[Option[BinaryKind]] = Some(BinaryKind.Executable)
@@ -435,16 +475,53 @@ trait KotlinJSModule extends KotlinModule { outer =>
         globSelectors: Task[Seq[String]]
     ): Task[(String, Seq[TestResult])] = Task.Anon {
       // This is a terrible hack, but it works
-      run()()
+      run(Task.Anon {
+        Args(args() ++ Seq(
+          // TODO this is valid only for the NodeJS target. Once browser support is
+          //  added, need to have different argument handling
+          "--require",
+          sourceMapSupportModule().path.toString(),
+          mochaModule().path.toString()
+        ))
+      })()
       ("", Seq.empty[TestResult])
     }
+
+    override def kotlinJSRunTarget: T[Option[RunTarget]] = Some(RunTarget.Node)
   }
 
-  trait KotlinJSKotlinXTests extends KotlinJSTests {
+  /**
+   * Run tests for Kotlin/JS target using `kotlin.test` package.
+   */
+  trait KotlinTestPackageTests extends KotlinJSTests {
     override def ivyDeps = Agg(
       ivy"org.jetbrains.kotlin:kotlin-test-js:${kotlinVersion()}"
     )
-    override def kotlinJSRunTarget: T[Option[RunTarget]] = Some(RunTarget.Node)
+  }
+
+  /**
+   * Run tests for Kotlin/JS target using Kotest framework.
+   */
+  trait KotestTests extends KotlinJSTests {
+
+    def kotestVersion: T[String] = "5.9.1"
+
+    private def kotestProcessor = Task {
+      defaultResolver().resolveDeps(
+        Agg(
+          ivy"io.kotest:kotest-framework-multiplatform-plugin-embeddable-compiler-jvm:${kotestVersion()}"
+        )
+      ).head
+    }
+
+    override def kotlincOptions = super.kotlincOptions() ++ Seq(
+      s"-Xplugin=${kotestProcessor().path}"
+    )
+
+    override def ivyDeps = Agg(
+      ivy"io.kotest:kotest-framework-engine-js:${kotestVersion()}",
+      ivy"io.kotest:kotest-assertions-core-js:${kotestVersion()}"
+    )
   }
 
   // endregion

kotlinlib/test/resources/kotlin-js/foo/test/src/foo/HelloKotestTests.kt

@@ -0,0 +1,16 @@
+package foo
+
+import bar.getString
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+
+class HelloTests: FunSpec({
+
+    test("success") {
+        getString() shouldBe "Hello, world"
+    }
+
+    test("failure") {
+        getString() shouldBe "Not hello, world"
+    }
+})

kotlinlib/test/src/mill/kotlinlib/js/KotlinJSKotestModuleTests.scala

@@ -0,0 +1,56 @@
+package mill
+package kotlinlib.js
+
+import mill.eval.EvaluatorPaths
+import mill.testkit.{TestBaseModule, UnitTester}
+import utest.{assert, TestSuite, Tests, test}
+
+object KotlinJSKotestModuleTests extends TestSuite {
+
+  private val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "kotlin-js"
+
+  private val kotlinVersion = "1.9.25"
+
+  object module extends TestBaseModule {
+
+    object bar extends KotlinJSModule {
+      def kotlinVersion = KotlinJSKotestModuleTests.kotlinVersion
+    }
+
+    object foo extends KotlinJSModule {
+      def kotlinVersion = KotlinJSKotestModuleTests.kotlinVersion
+      override def moduleDeps = Seq(module.bar)
+
+      object test extends KotlinJSModule with KotestTests {
+        override def allSourceFiles = super.allSourceFiles()
+          .filter(!_.path.toString().endsWith("HelloKotlinTestPackageTests.kt"))
+      }
+    }
+  }
+
+  private def testEval() = UnitTester(module, resourcePath)
+
+  def tests: Tests = Tests {
+
+    test("run tests") {
+      val eval = testEval()
+
+      val command = module.foo.test.test()
+      val Left(_) = eval.apply(command)
+
+      // temporary, because we are running run() task, it won't be test.log, but run.log
+      val log =
+        os.read(EvaluatorPaths.resolveDestPaths(eval.outPath, command).log / ".." / "run.log")
+      assert(
+        log.contains(
+          "AssertionFailedError: expected:<\"Not hello, world\"> but was:<\"Hello, world\">"
+        ),
+        log.contains("1 passing"),
+        log.contains("1 failing"),
+        // verify that source map is applied, otherwise all stack entries will point to .js
+        log.contains("HelloKotestTests.kt:")
+      )
+    }
+  }
+
+}

kotlinlib/test/src/mill/kotlinlib/js/KotlinJSKotlinTestPackageModuleTests.scala

@@ -0,0 +1,55 @@
+package mill
+package kotlinlib
+package js
+
+import mill.eval.EvaluatorPaths
+import mill.testkit.{TestBaseModule, UnitTester}
+import utest.{assert, TestSuite, Tests, test}
+
+object KotlinJSKotlinTestPackageModuleTests extends TestSuite {
+
+  private val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "kotlin-js"
+
+  private val kotlinVersion = "1.9.25"
+
+  object module extends TestBaseModule {
+
+    object bar extends KotlinJSModule {
+      def kotlinVersion = KotlinJSKotlinTestPackageModuleTests.kotlinVersion
+    }
+
+    object foo extends KotlinJSModule {
+      def kotlinVersion = KotlinJSKotlinTestPackageModuleTests.kotlinVersion
+      override def moduleDeps = Seq(module.bar)
+
+      object test extends KotlinJSModule with KotlinTestPackageTests {
+        override def allSourceFiles = super.allSourceFiles()
+          .filter(!_.path.toString().endsWith("HelloKotestTests.kt"))
+      }
+    }
+  }
+
+  private def testEval() = UnitTester(module, resourcePath)
+
+  def tests: Tests = Tests {
+
+    test("run tests") {
+      val eval = testEval()
+
+      val command = module.foo.test.test()
+      val Left(_) = eval.apply(command)
+
+      // temporary, because we are running run() task, it won't be test.log, but run.log
+      val log =
+        os.read(EvaluatorPaths.resolveDestPaths(eval.outPath, command).log / ".." / "run.log")
+      assert(
+        log.contains("AssertionError: Expected <Hello, world>, actual <Not hello, world>."),
+        log.contains("1 passing"),
+        log.contains("1 failing"),
+        // verify that source map is applied, otherwise all stack entries will point to .js
+        log.contains("HelloKotlinTestPackageTests.kt:")
+      )
+    }
+  }
+
+}