Support for explicit public API markers (Kotlin#116)

* Add support for defining public declarations explicitly

If the added properties are used, all unmatched declarations will be excluded
from the API check. If properties for both ignored and explicit markers are set,
filtering of ignored declarations will happen after filtering of declarations
not explicitly marked as public.

* Support validation of non-main source sets for kotlin-jvm projects

src/functionalTest/kotlin/kotlinx/validation/test/MixedMarkersTest.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.validation.test
+
+import kotlinx.validation.api.*
+import kotlinx.validation.api.buildGradleKts
+import kotlinx.validation.api.kotlin
+import kotlinx.validation.api.resolve
+import kotlinx.validation.api.test
+import org.junit.Test
+
+class MixedMarkersTest : BaseKotlinGradleTest() {
+
+    @Test
+    fun testMixedMarkers() {
+        val runner = test {
+            buildGradleKts {
+                resolve("examples/gradle/base/withPlugin.gradle.kts")
+                resolve("examples/gradle/configuration/publicMarkers/mixedMarkers.gradle.kts")
+            }
+
+            kotlin("MixedAnnotations.kt") {
+                resolve("examples/classes/MixedAnnotations.kt")
+            }
+
+            apiFile(projectName = rootProjectDir.name) {
+                resolve("examples/classes/MixedAnnotations.dump")
+            }
+
+            runner {
+                arguments.add(":apiCheck")
+            }
+        }
+
+        runner.withDebug(true).build().apply {
+            assertTaskSuccess(":apiCheck")
+        }
+    }
+}

src/functionalTest/kotlin/kotlinx/validation/test/PublicMarkersTest.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.validation.test
+
+import kotlinx.validation.api.*
+import kotlinx.validation.api.buildGradleKts
+import kotlinx.validation.api.kotlin
+import kotlinx.validation.api.resolve
+import kotlinx.validation.api.test
+import org.junit.Test
+
+class PublicMarkersTest : BaseKotlinGradleTest() {
+
+    @Test
+    fun testPublicMarkers() {
+        val runner = test {
+            buildGradleKts {
+                resolve("examples/gradle/base/withPlugin.gradle.kts")
+                resolve("examples/gradle/configuration/publicMarkers/markers.gradle.kts")
+            }
+
+            kotlin("ClassWithPublicMarkers.kt") {
+                resolve("examples/classes/ClassWithPublicMarkers.kt")
+            }
+
+            kotlin("ClassInPublicPackage.kt") {
+                resolve("examples/classes/ClassInPublicPackage.kt")
+            }
+
+            apiFile(projectName = rootProjectDir.name) {
+                resolve("examples/classes/ClassWithPublicMarkers.dump")
+            }
+
+            runner {
+                arguments.add(":apiCheck")
+            }
+        }
+
+        runner.withDebug(true).build().apply {
+            assertTaskSuccess(":apiCheck")
+        }
+    }
+}

src/functionalTest/resources/examples/classes/ClassInPublicPackage.kt

@@ -0,0 +1,10 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package foo.api
+
+class ClassInPublicPackage {
+    class Inner
+}

src/functionalTest/resources/examples/classes/ClassWithPublicMarkers.dump

@@ -0,0 +1,23 @@
+public final class foo/ClassWithPublicMarkers {
+	public final fun getBar1 ()I
+	public final fun getBar2 ()I
+	public final fun setBar1 (I)V
+	public final fun setBar2 (I)V
+}
+
+public final class foo/ClassWithPublicMarkers$MarkedClass {
+	public fun <init> ()V
+	public final fun getBar1 ()I
+}
+
+public abstract interface annotation class foo/PublicClass : java/lang/annotation/Annotation {
+}
+
+public final class foo/api/ClassInPublicPackage {
+	public fun <init> ()V
+}
+
+public final class foo/api/ClassInPublicPackage$Inner {
+	public fun <init> ()V
+}
+

src/functionalTest/resources/examples/classes/ClassWithPublicMarkers.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package foo
+
+@Target(AnnotationTarget.CLASS)
+annotation class PublicClass
+
+@Target(AnnotationTarget.FIELD)
+annotation class PublicField
+
+@Target(AnnotationTarget.PROPERTY)
+annotation class PublicProperty
+
+public class ClassWithPublicMarkers {
+    @PublicField
+    var bar1 = 42
+
+    @PublicProperty
+    var bar2 = 42
+
+    @PublicClass
+    class MarkedClass {
+        val bar1 = 41
+    }
+
+    var notMarkedPublic = 42
+
+    class NotMarkedClass
+}

src/functionalTest/resources/examples/classes/MixedAnnotations.dump

@@ -0,0 +1,5 @@
+public final class mixed/MarkedPublicWithPrivateMembers {
+	public fun <init> ()V
+	public final fun otherFun ()V
+}
+

src/functionalTest/resources/examples/classes/MixedAnnotations.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package mixed
+
+@Target(AnnotationTarget.CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.FUNCTION)
+annotation class PublicApi
+
+@Target(AnnotationTarget.CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.FUNCTION)
+annotation class PrivateApi
+
+@PublicApi
+class MarkedPublicWithPrivateMembers {
+    @PrivateApi
+    var private1 = 42
+
+    @field:PrivateApi
+    var private2 = 15
+
+    @PrivateApi
+    fun privateFun() = Unit
+
+    @PublicApi
+    @PrivateApi
+    fun privateFun2() = Unit
+
+    fun otherFun() = Unit
+}
+
+// Member annotations should be ignored in explicitly private classes
+@PrivateApi
+class MarkedPrivateWithPublicMembers {
+    @PublicApi
+    var public1 = 42
+
+    @field:PublicApi
+    var public2 = 15
+
+    @PublicApi
+    fun publicFun() = Unit
+
+    fun otherFun() = Unit
+}
+
+@PrivateApi
+@PublicApi
+class PublicAndPrivateFilteredOut

src/functionalTest/resources/examples/gradle/configuration/publicMarkers/markers.gradle.kts

@@ -0,0 +1,13 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+configure<kotlinx.validation.ApiValidationExtension> {
+    publicMarkers.add("foo.PublicClass")
+    publicMarkers.add("foo.PublicField")
+    publicMarkers.add("foo.PublicProperty")
+
+    publicPackages.add("foo.api")
+    publicClasses.add("foo.PublicClass")
+}

src/functionalTest/resources/examples/gradle/configuration/publicMarkers/mixedMarkers.gradle.kts

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+configure<kotlinx.validation.ApiValidationExtension> {
+    nonPublicMarkers.add("mixed.PrivateApi")
+    publicMarkers.add("mixed.PublicApi")
+}

src/main/kotlin/ApiValidationExtension.kt

@@ -34,4 +34,34 @@ open class ApiValidationExtension {
      * Example of such a class could be `com.package.android.BuildConfig`.
      */
     public var ignoredClasses: MutableSet<String> = HashSet()
+
+    /**
+     * Fully qualified names of annotations that can be used to explicitly mark public declarations. 
+     * If at least one of [publicMarkers], [publicPackages] or [publicClasses] is defined,
+     * all declarations not covered by any of them will be considered non-public. 
+     * [ignoredPackages], [ignoredClasses] and [nonPublicMarkers] can be used for additional filtering.
+     */
+    public var publicMarkers: MutableSet<String> = HashSet()
+
+    /**
+     * Fully qualified package names that contain public declarations. 
+     * If at least one of [publicMarkers], [publicPackages] or [publicClasses] is defined,
+     * all declarations not covered by any of them will be considered non-public. 
+     * [ignoredPackages], [ignoredClasses] and [nonPublicMarkers] can be used for additional filtering.
+     */
+    public var publicPackages: MutableSet<String> = HashSet()
+
+    /**
+     * Fully qualified names of public classes.
+     * If at least one of [publicMarkers], [publicPackages] or [publicClasses] is defined,
+     * all declarations not covered by any of them will be considered non-public.
+     * [ignoredPackages], [ignoredClasses] and [nonPublicMarkers] can be used for additional filtering.
+     */
+    public var publicClasses: MutableSet<String> = HashSet()
+
+    /**
+     * Non-default Gradle SourceSet names that should be validated.
+     * By default, only the `main` source set is checked.
+     */
+    public var additionalSourceSets: MutableSet<String> = HashSet()
 }

src/main/kotlin/BinaryCompatibilityValidatorPlugin.kt

@@ -130,12 +130,7 @@ class BinaryCompatibilityValidatorPlugin : Plugin<Project> {
         project: Project,
         extension: ApiValidationExtension
     ) = configurePlugin("kotlin", project, extension) {
-        project.sourceSets.all { sourceSet ->
-            if (sourceSet.name != SourceSet.MAIN_SOURCE_SET_NAME) {
-                return@all
-            }
-            project.configureApiTasks(sourceSet, extension, TargetConfig(project))
-        }
+        project.configureApiTasks(extension, TargetConfig(project))
     }
 }
 
@@ -225,19 +220,24 @@ fun apiCheckEnabled(projectName: String, extension: ApiValidationExtension): Boo
     projectName !in extension.ignoredProjects && !extension.validationDisabled
 
 private fun Project.configureApiTasks(
-    sourceSet: SourceSet,
     extension: ApiValidationExtension,
     targetConfig: TargetConfig = TargetConfig(this),
 ) {
     val projectName = project.name
     val apiBuildDir = targetConfig.apiDir.map { buildDir.resolve(it) }
+    val sourceSetsOutputsProvider = project.provider {
+        sourceSets
+            .filter { it.name == SourceSet.MAIN_SOURCE_SET_NAME || it.name in extension.additionalSourceSets }
+            .map { it.output.classesDirs }
+    }
+
     val apiBuild = task<KotlinApiBuildTask>(targetConfig.apiTaskName("Build")) {
         isEnabled = apiCheckEnabled(projectName, extension)
         // 'group' is not specified deliberately, so it will be hidden from ./gradlew tasks
         description =
             "Builds Kotlin API for 'main' compilations of $projectName. Complementary task and shouldn't be called manually"
-        inputClassesDirs = files(provider<Any> { if (isEnabled) sourceSet.output.classesDirs else emptyList<Any>() })
-        inputDependencies = files(provider<Any> { if (isEnabled) sourceSet.output.classesDirs else emptyList<Any>() })
+        inputClassesDirs = files(provider<Any> { if (isEnabled) sourceSetsOutputsProvider.get() else emptyList<Any>() })
+        inputDependencies = files(provider<Any> { if (isEnabled) sourceSetsOutputsProvider.get() else emptyList<Any>() })
         outputApiDir = apiBuildDir.get()
     }
 

src/main/kotlin/KotlinApiBuildTask.kt

@@ -53,6 +53,24 @@ open class KotlinApiBuildTask @Inject constructor(
         get() = _ignoredClasses ?: extension?.ignoredClasses ?: emptySet()
         set(value) { _ignoredClasses = value }
 
+    private var _publicPackages: Set<String>? = null
+    @get:Input
+    var publicPackages: Set<String>
+        get() = _publicPackages ?: extension?.publicPackages ?: emptySet()
+        set(value) { _publicPackages = value }
+
+    private var _publicMarkers: Set<String>? = null
+    @get:Input
+    var publicMarkers: Set<String>
+        get() = _publicMarkers ?: extension?.publicMarkers ?: emptySet()
+        set(value) { _publicMarkers = value}
+
+    private var _publicClasses: Set<String>? = null
+    @get:Input
+    var publicClasses: Set<String>
+        get() = _publicClasses ?: extension?.publicClasses ?: emptySet()
+        set(value) { _publicClasses = value }
+
     @get:Internal
     internal val projectName = project.name
 
@@ -79,8 +97,9 @@ open class KotlinApiBuildTask @Inject constructor(
 
 
         val filteredSignatures = signatures
+            .retainExplicitlyIncludedIfDeclared(publicPackages, publicClasses, publicMarkers)
             .filterOutNonPublic(ignoredPackages, ignoredClasses)
-            .filterOutAnnotated(nonPublicMarkers.map { it.replace(".", "/") }.toSet())
+            .filterOutAnnotated(nonPublicMarkers.map(::replaceDots).toSet())
 
         outputApiDir.resolve("$projectName.api").bufferedWriter().use { writer ->
             filteredSignatures