[Gradle][MPP] Implement initial MultiplatformAndroidSourceSetLayoutV2DiagnosticsTest

... to cover KT-53709

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/android/checker/KotlinAndroidSourceSetLayoutChecker.kt

@@ -14,7 +14,7 @@ import org.jetbrains.kotlin.gradle.plugin.sources.android.KotlinAndroidSourceSet
 import org.jetbrains.kotlin.gradle.utils.SingleWarningPerBuild
 
 internal interface KotlinAndroidSourceSetLayoutChecker {
-    class ProjectMisconfiguredException(message: String) : Exception(message)
+    open class ProjectMisconfiguredException(message: String) : Exception(message)
 
     interface DiagnosticReporter {
         fun error(diagnostic: Diagnostic): Nothing

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/assertions.kt

@@ -90,4 +90,9 @@ fun Project.assertNotContainsDependencies(configurationName: String, vararg depe
         foundUnexpectedDependencies.isEmpty(),
         "Unexpected dependencies '$foundUnexpectedDependencies' found in configuration '$configurationName'"
     )
+}
+
+inline fun <reified T> assertIsInstance(value: Any?): T {
+    if (value is T) return value
+    fail("Expected $value to implement ${T::class.java}")
 }

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/sources/android/MultiplatformAndroidSourceSetLayoutV2DiagnosticsTest.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("FunctionName")
+
+package org.jetbrains.kotlin.gradle.sources.android
+
+import com.android.build.gradle.LibraryPlugin
+import org.gradle.api.Project
+import org.gradle.api.internal.project.ProjectInternal
+import org.jetbrains.kotlin.gradle.*
+import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
+import org.jetbrains.kotlin.gradle.plugin.sources.android.checker.MultiplatformLayoutV2AndroidStyleSourceDirUsageChecker.AndroidStyleSourceDirUsageDiagnostic
+import org.jetbrains.kotlin.gradle.plugin.sources.android.findAndroidSourceSet
+import org.jetbrains.kotlin.gradle.plugin.sources.android.multiplatformAndroidSourceSetLayoutV2
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class MultiplatformAndroidSourceSetLayoutV2DiagnosticsTest {
+
+    private val diagnosticsReporter = TestDiagnosticsReporter()
+
+    private fun buildMinimalAndroidMultiplatformProject(): ProjectInternal = buildProjectWithMPP {
+        setMultiplatformAndroidSourceSetLayoutVersion(2)
+        plugins.apply(LibraryPlugin::class.java)
+        androidLibrary {
+            compileSdk = 31
+        }
+        kotlin {
+            android()
+        }
+    }
+
+    private fun Project.checkCreatedSourceSets(
+        diagnosticsReporter: TestDiagnosticsReporter = this@MultiplatformAndroidSourceSetLayoutV2DiagnosticsTest.diagnosticsReporter
+    ) {
+        /* Invoke checkers on all source sets */
+        project.multiplatformExtension.sourceSets.forEach { kotlinSourceSet ->
+            val androidSourceSet = project.findAndroidSourceSet(kotlinSourceSet) ?: return@forEach
+            multiplatformAndroidSourceSetLayoutV2.checker.checkCreatedSourceSet(
+                diagnosticReporter = diagnosticsReporter,
+                target = project.multiplatformExtension.android(),
+                layout = multiplatformAndroidSourceSetLayoutV2,
+                kotlinSourceSet = kotlinSourceSet,
+                androidSourceSet = androidSourceSet
+            )
+        }
+    }
+
+    @Test
+    fun `test - KT-53709 - androidTest_kotlin in use`() {
+
+        val project = buildMinimalAndroidMultiplatformProject()
+
+        /* Ensure that the problematic androidTest/kotlin source dir is 'in use' */
+        val androidTestKotlinSourceDir = project.file("src/androidTest/kotlin")
+        androidTestKotlinSourceDir.mkdirs()
+        project.evaluate()
+
+        /* Invoke checkers on all source sets */
+        project.checkCreatedSourceSets()
+
+        val diagnostic = assertIsInstance<AndroidStyleSourceDirUsageDiagnostic>(diagnosticsReporter.assertSingleWarning())
+        assertEquals(androidTestKotlinSourceDir, diagnostic.androidStyleSourceDirInUse)
+        assertEquals(project.file("src/androidInstrumentedTest/kotlin"), diagnostic.kotlinStyleSourceDirToUse)
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/sources/android/TestDiagnosticsReporter.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.sources.android
+
+import org.jetbrains.kotlin.gradle.plugin.sources.android.checker.KotlinAndroidSourceSetLayoutChecker
+import kotlin.test.fail
+
+internal class TestDiagnosticsReporter : KotlinAndroidSourceSetLayoutChecker.DiagnosticReporter {
+
+    class ErrorDiagnosticException(val diagnostic: KotlinAndroidSourceSetLayoutChecker.Diagnostic) :
+        KotlinAndroidSourceSetLayoutChecker.ProjectMisconfiguredException(diagnostic.message)
+
+    private val _errors = mutableListOf<KotlinAndroidSourceSetLayoutChecker.Diagnostic>()
+
+    private val _warnings = mutableListOf<KotlinAndroidSourceSetLayoutChecker.Diagnostic>()
+
+    val errors get() = _errors.toList()
+
+    val warnings get() = _warnings.toList()
+
+    override fun error(diagnostic: KotlinAndroidSourceSetLayoutChecker.Diagnostic): Nothing {
+        _errors.add(diagnostic)
+        throw ErrorDiagnosticException(diagnostic)
+    }
+
+    override fun warning(diagnostic: KotlinAndroidSourceSetLayoutChecker.Diagnostic) {
+        _warnings.add(diagnostic)
+    }
+}
+
+internal fun TestDiagnosticsReporter.assertSingleWarning(): KotlinAndroidSourceSetLayoutChecker.Diagnostic {
+    if (errors.isNotEmpty()) fail("Expected just a single warning, but found errors: $errors")
+    if (warnings.isEmpty()) fail("Expected a single warning, but found none!")
+    if (warnings.size > 1) fail("Expected a single warning, but found multiple: $warnings")
+    return warnings.first()
+}