Add tests for java-library support.

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginMultiVersionIT.kt

@@ -2,6 +2,7 @@ package org.jetbrains.kotlin.gradle
 
 import org.jetbrains.kotlin.gradle.util.getFileByName
 import org.jetbrains.kotlin.gradle.util.modify
+import org.junit.Assume
 import org.junit.Test
 import java.io.File
 import java.util.zip.ZipFile
@@ -125,4 +126,35 @@ class KotlinGradlePluginMultiVersionIT : BaseMultiGradleVersionIT() {
             assertContains(":compileKotlin", ":compileTestKotlin")
         }
     }
+
+    @Test
+    fun testJavaLibraryCompatibility() {
+        Assume.assumeTrue("The java-library plugin is supported only in Gradle 3.4+ (current: $gradleVersion)",
+                gradleVersion.split(".").map(String::toInt).let { (major, minor) ->
+                    major > 3 || major == 3 && minor >= 4
+                })
+
+        val project = Project("javaLibraryProject", gradleVersion)
+        val compileKotlinTasks = listOf(":libA:compileKotlin", ":libB:compileKotlin", ":app:compileKotlin")
+        project.build("build") {
+            assertSuccessful()
+            assertNotContains("Could not register Kotlin output")
+            assertTasksExecuted(compileKotlinTasks)
+        }
+
+        // Modify a library source and its usage and re-build the project:
+        for (path in listOf("libA/src/main/kotlin/HelloA.kt", "libB/src/main/kotlin/HelloB.kt", "app/src/main/kotlin/App.kt")) {
+            File(project.projectDir, path).modify { original ->
+                original.replace("helloA", "helloA1")
+                        .replace("helloB", "helloB1")
+                        .apply { assert(!equals(original)) }
+            }
+        }
+
+        project.build("build") {
+            assertSuccessful()
+            assertNotContains("Could not register Kotlin output")
+            assertTasksExecuted(compileKotlinTasks)
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/app/build.gradle

@@ -0,0 +1,7 @@
+apply plugin: 'java'
+apply plugin: 'kotlin'
+
+dependencies {
+    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+    compile project(':libB')
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/app/src/main/kotlin/App.kt

@@ -0,0 +1,6 @@
+import com.example.*
+
+fun main(args: Array<String>) {
+    println(helloA())
+    println(helloB())
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/build.gradle

@@ -0,0 +1,14 @@
+buildscript {
+    repositories {
+        mavenLocal()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+subprojects {
+    repositories {
+        mavenLocal()
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/libA/build.gradle

@@ -0,0 +1,6 @@
+apply plugin: 'java-library'
+apply plugin: 'kotlin'
+
+dependencies {
+    api "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/libA/src/main/kotlin/HelloA.kt

@@ -0,0 +1,3 @@
+package com.example
+
+fun helloA() = "Hello"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/libB/build.gradle

@@ -0,0 +1,7 @@
+apply plugin: 'java-library'
+apply plugin: 'kotlin'
+
+dependencies {
+    api "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+    api project(':libA')
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/libB/src/main/kotlin/HelloB.kt

@@ -0,0 +1,3 @@
+package com.example
+
+fun helloB() = helloA()

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/javaLibraryProject/settings.gradle

@@ -0,0 +1 @@
+include ':libA', ':libB', ':app'