Select the asserter based on test framework presence in classpath

Simplify asserter lookup: enumerate all AsserterContributors when
the file class with lookupAsserter function is initialized.

It's assumed that AsserterContributor initialization should be fast.

#KT-21154 Fixed

libraries/kotlin.test/junit/src/main/kotlin/JUnitSupport.kt

@@ -3,21 +3,25 @@ package kotlin.test.junit
 import org.junit.*
 import kotlin.test.*
 
+/**
+ * Provides [JUnitAsserter] if `org.junit.Assert` is found in the classpath.
+ */
 class JUnitContributor : AsserterContributor {
     override fun contribute(): Asserter? {
-        for (stackFrame in currentStackTrace()) {
-            @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
-            val className = stackFrame.className as java.lang.String
+        return if (hasJUnitInClassPath) JUnitAsserter else null
+    }
 
-            if (className.startsWith("org.junit.") || className.startsWith("junit.")) {
-                return JUnitAsserter
-            }
-        }
-
-        return null
+    private val hasJUnitInClassPath = try {
+        Class.forName("org.junit.Assert")
+        true
+    } catch (_: ClassNotFoundException) {
+        false
     }
 }
 
+/**
+ * Implements `kotlin.test` assertions by delegating them to `org.junit.Assert` class.
+ */
 object JUnitAsserter : Asserter {
     override fun assertEquals(message: String?, expected: Any?, actual: Any?) {
         Assert.assertEquals(message, expected, actual)

libraries/kotlin.test/junit/src/test/kotlin/JUnitContributorTest.kt

@@ -1,27 +1,26 @@
 package kotlin.test.junit.tests
 
-import org.junit.*
+import org.junit.Assert
+import kotlin.test.*
 import java.util.concurrent.*
+import kotlin.test.junit.JUnitAsserter
 
 class JUnitContributorTest {
     @Test
     fun smokeTest() {
-        Assert.assertEquals("JUnitAsserter", asserter.`class`.simpleName)
+        assertSame(JUnitAsserter, kotlin.test.asserter)
+        Assert.assertEquals(JUnitAsserter::class.java.simpleName, kotlin.test.asserter.javaClass.simpleName)
     }
 
     @Test
-    fun `should fail to contribute if it was run outside of junit`() {
-        @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
-        val q = ArrayBlockingQueue<java.lang.Object>(1)
+    fun parallelThreadGetsTheSameAsserter() {
+        val q = ArrayBlockingQueue<Any>(1)
 
         Thread {
             q.put(asserter)
         }.start()
 
-        Assert.assertEquals("DefaultAsserter", q.take().`class`.simpleName)
+        assertSame(kotlin.test.asserter, q.take())
     }
 
-    @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
-    private val asserter: java.lang.Object
-        get() = Class.forName("kotlin.test.AssertionsKt").getMethod("getAsserter").invoke(null) as java.lang.Object
 }

libraries/kotlin.test/jvm/src/main/kotlin/AsserterLookup.kt

@@ -1,48 +1,15 @@
 package kotlin.test
 
-import java.util.*
-import java.util.concurrent.atomic.*
-import java.util.concurrent.locks.*
-import kotlin.concurrent.withLock
+import java.util.ServiceLoader
 
-private val inited = AtomicBoolean()
-private val lock = ReentrantLock()
-private val contributors = ArrayList<AsserterContributor>()
-
-internal actual fun lookupAsserter(): Asserter = lookup()
+private val contributors = ServiceLoader.load(AsserterContributor::class.java).toList()
 
 private val defaultAsserter = DefaultAsserter()
 
-internal fun lookup(): Asserter {
-    initContributorsIfNeeded()
-
+internal actual fun lookupAsserter(): Asserter {
     for (contributor in contributors) {
         val asserter = contributor.contribute()
-        if (asserter != null) {
-            return asserter
-        }
+        if (asserter != null) return asserter
     }
-
     return defaultAsserter
-}
-
-private fun initContributors() {
-    contributors.clear()
-    val loader = ServiceLoader.load(AsserterContributor::class.java)
-
-    for (contributor in loader) {
-        if (contributor != null) {
-            contributors.add(contributor)
-        }
-    }
-}
-
-private fun initContributorsIfNeeded() {
-    if (!inited.get()) {
-        lock.withLock {
-            if (inited.compareAndSet(false, true)) {
-                initContributors()
-            }
-        }
-    }
-}
+}

libraries/kotlin.test/testng/src/main/kotlin/TestNGSupport.kt

@@ -8,20 +8,25 @@ package kotlin.test.testng
 import org.testng.*
 import kotlin.test.*
 
+/**
+ * Provides [TestNGAsserter] if `org.testng.Assert` is found in the classpath.
+ */
 class TestNGContributor : AsserterContributor {
     override fun contribute(): Asserter? {
-        for (stackFrame in currentStackTrace()) {
-            val className = stackFrame.className
+        return if (hasTestNGInClassPath) TestNGAsserter else null
+    }
 
-            if (className.startsWith("org.testng.") || className.startsWith("testng.")) {
-                return TestNGAsserter
-            }
-        }
-
-        return null
+    private val hasTestNGInClassPath = try {
+        Class.forName("org.testng.Assert")
+        true
+    } catch (_: ClassNotFoundException) {
+        false
     }
 }
 
+/**
+ * Implements `kotlin.test` assertions by delegating them to `org.testng.Assert` class.
+ */
 object TestNGAsserter : Asserter {
     override fun assertEquals(message: String?, expected: Any?, actual: Any?) {
         Assert.assertEquals(expected, actual, message)

libraries/kotlin.test/testng/src/test/kotlin/TestNGContributorTest.kt

@@ -1,25 +1,27 @@
 package kotlin.test.testng.tests
 
-import org.testng.annotations.*
-import org.testng.*
+import org.testng.Assert
+import kotlin.test.*
 import java.util.concurrent.*
+import kotlin.test.testng.TestNGAsserter
 
 class TestNGContributorTest {
 
     @Test
     fun smokeTest() {
-        Assert.assertEquals("TestNGAsserter", kotlin.test.asserter.javaClass.simpleName)
+        assertSame(TestNGAsserter, asserter)
+        Assert.assertEquals(TestNGAsserter::class.java.simpleName, kotlin.test.asserter.javaClass.simpleName)
     }
 
     @Test
-    fun `should fail to contribute if it was run outside of testng`() {
+    fun parallelThreadGetsTheSameAsserter() {
         val q = ArrayBlockingQueue<Any>(1)
 
         Thread {
-            q.put(kotlin.test.asserter)
+            q.put(asserter)
         }.start()
 
-        Assert.assertEquals("DefaultAsserter", q.take().javaClass.simpleName)
+        assertSame(asserter, q.take())
     }
 
-}
+}