Emit Scala.js JUnit bootstrappers for JUnit test classes.

This allows Scala.js for dotty to support normal JUnit tests.

Author: sjrd

.drone.yml

@@ -31,7 +31,7 @@ pipeline:
     image: lampepfl/dotty:2019-04-22
     commands:
       - cp -R . /tmp/2/ && cd /tmp/2/
-      - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test; dotty-semanticdb/compile; dotty-semanticdb/test:compile;sjsSandbox/run"
+      - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test; dotty-semanticdb/compile; dotty-semanticdb/test:compile;sjsSandbox/run;sjsSandbox/test"
       - ./project/scripts/bootstrapCmdTests
 
   community_build:

compiler/src/dotty/tools/backend/sjs/JSDefinitions.scala

@@ -189,4 +189,40 @@ final class JSDefinitions()(implicit ctx: Context) {
   def isJSThisFunctionClass(cls: Symbol): Boolean =
     isScalaJSVarArityClass(cls, "ThisFunction")
 
+  /** Definitions related to the treatment of JUnit boostrappers. */
+  object junit {
+    lazy val TestAnnotType: TypeRef = ctx.requiredClassRef("org.junit.Test")
+    def TestAnnotClass(implicit ctx: Context): ClassSymbol = TestAnnotType.symbol.asClass
+
+    lazy val BeforeAnnotType: TypeRef = ctx.requiredClassRef("org.junit.Before")
+    def BeforeAnnotClass(implicit ctx: Context): ClassSymbol = BeforeAnnotType.symbol.asClass
+
+    lazy val AfterAnnotType: TypeRef = ctx.requiredClassRef("org.junit.After")
+    def AfterAnnotClass(implicit ctx: Context): ClassSymbol = AfterAnnotType.symbol.asClass
+
+    lazy val BeforeClassAnnotType: TypeRef = ctx.requiredClassRef("org.junit.BeforeClass")
+    def BeforeClassAnnotClass(implicit ctx: Context): ClassSymbol = BeforeClassAnnotType.symbol.asClass
+
+    lazy val AfterClassAnnotType: TypeRef = ctx.requiredClassRef("org.junit.AfterClass")
+    def AfterClassAnnotClass(implicit ctx: Context): ClassSymbol = AfterClassAnnotType.symbol.asClass
+
+    lazy val IgnoreAnnotType: TypeRef = ctx.requiredClassRef("org.junit.Ignore")
+    def IgnoreAnnotClass(implicit ctx: Context): ClassSymbol = IgnoreAnnotType.symbol.asClass
+
+    lazy val BootstrapperType: TypeRef = ctx.requiredClassRef("org.scalajs.junit.Bootstrapper")
+
+    lazy val TestMetadataType: TypeRef = ctx.requiredClassRef("org.scalajs.junit.TestMetadata")
+
+    lazy val NoSuchMethodExceptionType: TypeRef = ctx.requiredClassRef("java.lang.NoSuchMethodException")
+
+    lazy val FutureType: TypeRef = ctx.requiredClassRef("scala.concurrent.Future")
+    def FutureClass(implicit ctx: Context): ClassSymbol = FutureType.symbol.asClass
+
+    private lazy val FutureModule_successfulR = ctx.requiredModule("scala.concurrent.Future").requiredMethodRef("successful")
+    def FutureModule_successful(implicit ctx: Context): Symbol = FutureModule_successfulR.symbol
+
+    private lazy val SuccessModule_applyR = ctx.requiredModule("scala.util.Success").requiredMethodRef(nme.apply)
+    def SuccessModule_apply(implicit ctx: Context): Symbol = SuccessModule_applyR.symbol
+  }
+
 }

compiler/src/dotty/tools/backend/sjs/JUnitBootstrappers.scala

@@ -0,0 +1,324 @@
+package dotty.tools.backend.sjs
+
+import scala.annotation.tailrec
+
+import dotty.tools.dotc._
+
+import dotty.tools.dotc.core._
+import Constants._
+import Contexts._
+import Decorators._
+import Flags._
+import Names._
+import NameOps._
+import Phases._
+import Scopes._
+import Symbols._
+import StdNames._
+import Types._
+
+import dotty.tools.dotc.transform.MegaPhase._
+
+/** Generates JUnit bootstrapper objects for Scala.js.
+ *
+ *  On the JVM, JUnit uses run-time reflection to list and invoke JUnit-related
+ *  methods. They are identified by annotations such as `@Test`, `@Before`,
+ *  etc. In Scala.js, there is no such reflection for methods and annotations,
+ *  so a different strategy is used: this phase performs the necessary
+ *  inspections at compile-time, and generates a so-called bootstrapper object
+ *  where all those metadata have been reified.
+ *
+ *  With an example: given the following JUnit test class:
+ *
+ *  ```
+ *  class MyTest {
+ *    @Before def myBefore(): Unit = ...
+ *    @Before def otherBefore(): Unit = ...
+ *
+ *    @Test def syncTest(): Unit = ...
+ *    @Test def asyncTest(): Future[Try[Unit]] = ...
+ *
+ *    @Ignore @Test def ignoredTest(): Unit = ...
+ *  }
+ *
+ *  object MyTest {
+ *    @AfterClass def myAfterClass(): Unit = ...
+ *  }
+ *  ```
+ *
+ *  this phase generates the following bootstrapper module class:
+ *
+ *  ```
+ *  object MyTest$scalajs$junit$bootstrapper extends Object with Bootstrapper {
+ *    def beforeClass(): Unit = {
+ *      // nothing, since there is no @BeforeClass method in object MyTest
+ *    }
+ *
+ *    def afterClass(): Unit = {
+ *      MyTest.myAfterClass()
+ *    }
+ *
+ *    def before(instance: Object): Unit = {
+ *      // typically 0 or 1, but also support 2 or more
+ *      instance.asInstanceOf[MyTest].myBefore()
+ *      instance.asInstanceOf[MyTest].otherBefore()
+ *    }
+ *
+ *    def after(instance: Object): Unit = {
+ *      // nothing, since there is no @After method in class MyTest
+ *    }
+ *
+ *    def tests(): Array[TestMetadata] = Array(
+ *      new TestMetadata("syncTest", false, new org.junit.Test()),
+ *      new TestMetadata("asyncTest", false, new org.junit.Test()),
+ *      new TestMetadata("ignoredTest", true, new org.junit.Test()),
+ *    )
+ *
+ *    def invokeTest(instance: Object, name: String): Future[Unit] = {
+ *      val castInstance: MyTest = instance.asInstanceOf[MyTest]
+ *      if ("syncTest".equals(name))
+ *        Future.successful(scala.util.Success(castInstance.syncTest()))
+ *      else if ("asyncTest".equals(name))
+ *        castInstance.asyncTest() // asyncTest() already returns a Future[Try[Unit]]
+ *      else if ("ignoredTest".equals(name))
+ *        Future.successful(scala.util.Success(castInstance.ignoredTest()))
+ *      else
+ *        throw new NoSuchMethodException(name)
+ *    }
+ *
+ *    def newInstance(): Object = new MyTest()
+ *  }
+ *  ```
+ *
+ *  Note that the support for test methods returning `Future`s is specific to
+ *  Scala.js, and not advertised as a public feature. It is necessary to test
+ *  some things in Scala.js itself, but outside users should use a testing
+ *  framework with official asynchronous support instead.
+ *
+ *  Because `Booststrapper` is annotated with `@EnableReflectiveInstantiation`,
+ *  the run-time implementation of JUnit for Scala.js can load the boostrapper
+ *  module using `scala.scalajs.reflect.Reflect`, and then use the methods of
+ *  Bootstrapper, which are implemented in the bootstrapper object, to perform
+ *  test discovery and invocation.
+ *
+ *  TODO At the moment, this phase does not handle `@Test` annotations with
+ *  parameters, notably the expected exception class. This should be handled at
+ *  some point in the future.
+ */
+class JUnitBootstrappers extends MiniPhase {
+  import JUnitBootstrappers._
+  import ast.tpd._
+  import JSDefinitions.jsdefn
+
+  def phaseName: String = "junitBootstrappers"
+
+  override def isEnabled(implicit ctx: Context): Boolean =
+    super.isEnabled && ctx.settings.scalajs.value
+
+  // The actual transform -------------------------------
+
+  override def transformPackageDef(tree: PackageDef)(implicit ctx: Context): Tree = {
+    val junitdefn = jsdefn.junit
+
+    @tailrec
+    def hasTests(sym: ClassSymbol): Boolean = {
+      sym.info.decls.exists(m => m.is(Method) && m.hasAnnotation(junitdefn.TestAnnotClass)) ||
+      sym.superClass.exists && hasTests(sym.superClass.asClass)
+    }
+
+    def isTestClass(sym: Symbol): Boolean = {
+      sym.isClass &&
+      !sym.is(ModuleClass | Abstract | Trait) &&
+      hasTests(sym.asClass)
+    }
+
+    val bootstrappers = tree.stats.collect {
+      case clDef: TypeDef if isTestClass(clDef.symbol) =>
+        genBootstrapper(clDef.symbol.asClass)
+    }
+
+    if (bootstrappers.isEmpty) tree
+    else cpy.PackageDef(tree)(tree.pid, tree.stats ::: bootstrappers)
+  }
+
+  private def genBootstrapper(testClass: ClassSymbol)(
+      implicit ctx: Context): TypeDef = {
+
+    val junitdefn = jsdefn.junit
+
+    /* The name of the boostrapper module. It is derived from the test class name by
+     * appending a specific suffix string mandated "by spec". It will indeed also be
+     * computed as such at run-time by the Scala.js JUnit Runtime support. Therefore,
+     * it must *not* be a dotc semantic name.
+     */
+    val bootstrapperName = (testClass.name ++ "$scalajs$junit$bootstrapper").toTermName
+
+    val owner = testClass.owner
+    val moduleSym = ctx.newCompleteModuleSymbol(owner, bootstrapperName,
+        Synthetic, Synthetic,
+        List(defn.ObjectType, junitdefn.BootstrapperType), newScope,
+        coord = testClass.span, assocFile = testClass.assocFile).entered
+    val classSym = moduleSym.moduleClass.asClass
+
+    val constr = genConstructor(classSym)
+
+    val testMethods = annotatedMethods(testClass, junitdefn.TestAnnotClass)
+
+    val defs = List(
+        genCallOnModule(classSym, junitNme.beforeClass, testClass.companionModule, junitdefn.BeforeClassAnnotClass),
+        genCallOnModule(classSym, junitNme.afterClass, testClass.companionModule, junitdefn.AfterClassAnnotClass),
+        genCallOnParam(classSym, junitNme.before, testClass, junitdefn.BeforeAnnotClass),
+        genCallOnParam(classSym, junitNme.after, testClass, junitdefn.AfterAnnotClass),
+        genTests(classSym, testMethods),
+        genInvokeTest(classSym, testClass, testMethods),
+        genNewInstance(classSym, testClass)
+    )
+
+    sbt.APIUtils.registerDummyClass(classSym)
+
+    ClassDef(classSym, constr, defs)
+  }
+
+  private def genConstructor(owner: ClassSymbol)(implicit ctx: Context): DefDef = {
+    val sym = ctx.newDefaultConstructor(owner).entered
+    DefDef(sym, {
+      Block(
+        Super(This(owner), nme.EMPTY.toTypeName, inConstrCall = true).select(defn.ObjectClass.primaryConstructor).appliedToNone :: Nil,
+        unitLiteral
+      )
+    })
+  }
+
+  private def genCallOnModule(owner: ClassSymbol, name: TermName, module: Symbol, annot: Symbol)(implicit ctx: Context): DefDef = {
+    val sym = ctx.newSymbol(owner, name, Synthetic | Method,
+        MethodType(Nil, Nil, defn.UnitType)).entered
+
+    DefDef(sym, {
+      if (module.exists) {
+        val calls = annotatedMethods(module.moduleClass.asClass, annot)
+          .map(m => Apply(ref(module).select(m), Nil))
+        Block(calls, unitLiteral)
+      } else {
+        unitLiteral
+      }
+    })
+  }
+
+  private def genCallOnParam(owner: ClassSymbol, name: TermName, testClass: ClassSymbol, annot: Symbol)(implicit ctx: Context): DefDef = {
+    val sym = ctx.newSymbol(owner, name, Synthetic | Method,
+        MethodType(junitNme.instance :: Nil, defn.ObjectType :: Nil, defn.UnitType)).entered
+
+    DefDef(sym, { (paramRefss: List[List[Tree]]) =>
+      val List(List(instanceParamRef)) = paramRefss
+      val calls = annotatedMethods(testClass, annot)
+        .map(m => Apply(instanceParamRef.cast(testClass.typeRef).select(m), Nil))
+      Block(calls, unitLiteral)
+    })
+  }
+
+  private def genTests(owner: ClassSymbol, tests: List[Symbol])(
+      implicit ctx: Context): DefDef = {
+
+    val junitdefn = jsdefn.junit
+
+    val sym = ctx.newSymbol(owner, junitNme.tests, Synthetic | Method,
+        MethodType(Nil, defn.ArrayOf(junitdefn.TestMetadataType))).entered
+
+    DefDef(sym, {
+      val metadata = for (test <- tests) yield {
+        val name = Literal(Constant(test.name.toString))
+        val ignored = Literal(Constant(test.hasAnnotation(junitdefn.IgnoreAnnotClass)))
+        // TODO Handle @Test annotations with arguments
+        // val reifiedAnnot = New(mydefn.TestAnnotType, test.getAnnotation(mydefn.TestAnnotClass).get.arguments)
+        val testAnnot = test.getAnnotation(junitdefn.TestAnnotClass).get
+        if (testAnnot.arguments.nonEmpty)
+          ctx.error("@Test annotations with arguments are not yet supported in Scala.js for dotty", testAnnot.tree.sourcePos)
+        val noArgConstr = junitdefn.TestAnnotType.member(nme.CONSTRUCTOR).suchThat(_.info.paramInfoss.head.isEmpty).symbol.asTerm
+        val reifiedAnnot = New(junitdefn.TestAnnotType, noArgConstr, Nil)
+        New(junitdefn.TestMetadataType, List(name, ignored, reifiedAnnot))
+      }
+      JavaSeqLiteral(metadata, TypeTree(junitdefn.TestMetadataType))
+    })
+  }
+
+  private def genInvokeTest(owner: ClassSymbol, testClass: ClassSymbol, tests: List[Symbol])(
+      implicit ctx: Context): DefDef = {
+
+    val junitdefn = jsdefn.junit
+
+    val sym = ctx.newSymbol(owner, junitNme.invokeTest, Synthetic | Method,
+        MethodType(List(junitNme.instance, junitNme.name), List(defn.ObjectType, defn.StringType), junitdefn.FutureType)).entered
+
+    DefDef(sym, { (paramRefss: List[List[Tree]]) =>
+      val List(List(instanceParamRef, nameParamRef)) = paramRefss
+      val castInstanceSym = ctx.newSymbol(sym, junitNme.castInstance, Synthetic, testClass.typeRef, coord = owner.span)
+      Block(
+        ValDef(castInstanceSym, instanceParamRef.cast(testClass.typeRef)) :: Nil,
+        tests.foldRight[Tree] {
+          val tp = junitdefn.NoSuchMethodExceptionType
+          val constr = tp.member(nme.CONSTRUCTOR).suchThat { c =>
+            c.info.paramInfoss.head.size == 1 &&
+            c.info.paramInfoss.head.head.isRef(defn.StringClass)
+          }.symbol.asTerm
+          Throw(New(tp, constr, nameParamRef :: Nil))
+        } { (test, next) =>
+          If(Literal(Constant(test.name.toString)).select(defn.Any_equals).appliedTo(nameParamRef),
+              genTestInvocation(testClass, test, ref(castInstanceSym)),
+              next)
+        }
+      )
+    })
+  }
+
+  private def genTestInvocation(testClass: ClassSymbol, testMethod: Symbol, instance: Tree)(
+      implicit ctx: Context): Tree = {
+
+    val junitdefn = jsdefn.junit
+
+    val resultType = testMethod.info.resultType
+    if (resultType.isRef(defn.UnitClass)) {
+      val newSuccess = ref(junitdefn.SuccessModule_apply).appliedTo(ref(defn.BoxedUnit_UNIT))
+      Block(
+          instance.select(testMethod).appliedToNone :: Nil,
+          ref(junitdefn.FutureModule_successful).appliedTo(newSuccess)
+      )
+    } else if (resultType.isRef(junitdefn.FutureClass)) {
+      instance.select(testMethod).appliedToNone
+    } else {
+      // We lie in the error message to not expose that we support async testing.
+      ctx.error("JUnit test must have Unit return type", testMethod.sourcePos)
+      EmptyTree
+    }
+  }
+
+  private def genNewInstance(owner: ClassSymbol, testClass: ClassSymbol)(implicit ctx: Context): DefDef = {
+    val sym = ctx.newSymbol(owner, junitNme.newInstance, Synthetic | Method,
+        MethodType(Nil, defn.ObjectType)).entered
+
+    DefDef(sym, New(testClass.typeRef, Nil))
+  }
+
+  private def castParam(param: Symbol, clazz: Symbol)(implicit ctx: Context): Tree =
+    ref(param).cast(clazz.typeRef)
+
+  private def annotatedMethods(owner: ClassSymbol, annot: Symbol)(implicit ctx: Context): List[Symbol] =
+    owner.info.decls.filter(m => m.is(Method) && m.hasAnnotation(annot))
+}
+
+object JUnitBootstrappers {
+
+  private object junitNme {
+    val beforeClass: TermName = termName("beforeClass")
+    val afterClass: TermName = termName("afterClass")
+    val before: TermName = termName("before")
+    val after: TermName = termName("after")
+    val tests: TermName = termName("tests")
+    val invokeTest: TermName = termName("invokeTest")
+    val newInstance: TermName = termName("newInstance")
+
+    val instance: TermName = termName("instance")
+    val name: TermName = termName("name")
+    val castInstance: TermName = termName("castInstance")
+  }
+
+}

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -112,6 +112,7 @@ class Compiler {
          new ExpandPrivate,          // Widen private definitions accessed from nested classes
          new RestoreScopes,          // Repair scopes rendered invalid by moving definitions in prior phases of the group
          new SelectStatic,           // get rid of selects that would be compiled into GetStatic
+         new sjs.JUnitBootstrappers, // Generate JUnit-specific bootstrapper classes for Scala.js (not enabled by default)
          new CollectEntryPoints,     // Find classes with main methods
          new CollectSuperCalls) ::   // Find classes that are called with super
     Nil