Manually wiring Android API dump

build.gradle.kts

@@ -1,3 +1,8 @@
+import kotlinx.validation.KotlinApiBuildTask
+import kotlinx.validation.KotlinApiCompareTask
+import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformType
+
 /*
  * Copyright (c) 2021 Touchlab
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
@@ -66,3 +71,65 @@ subprojects {
         }
     }
 }
+
+/*
+ * Workaround for https://github.com/Kotlin/binary-compatibility-validator/issues/315
+ *
+ * BCV only registers its Android API tasks for a compilation named "release", which is what
+ * `com.android.library` plus `androidTarget()` used to produce. The AGP 9 KMP plugin
+ * (`com.android.kotlin.multiplatform.library`) names its compilations `main`, `hostTest` and
+ * `deviceTest`, so BCV matches nothing, registers no tasks, and the Android dumps silently stop
+ * being validated or updated while the build stays green.
+ *
+ * BCV is in maintenance mode and the fix landed in the Kotlin Gradle plugin's built-in ABI
+ * validation instead (KT-85950, Kotlin 2.4.20). Until we migrate to that, register the missing
+ * `androidApi*` tasks by hand against the `main` compilation, mirroring what BCV does for
+ * `release`.
+ */
+subprojects {
+    afterEvaluate {
+        val kotlinExtension = extensions.findByType<KotlinMultiplatformExtension>() ?: return@afterEvaluate
+        val androidTarget = kotlinExtension.targets.findByName("android") ?: return@afterEvaluate
+        val androidMainCompilation = androidTarget.compilations.findByName("main") ?: return@afterEvaluate
+        if (tasks.names.contains("androidApiBuild")) return@afterEvaluate
+
+        // BCV only uses an `api/<target>/` subdirectory when a module has more than one JVM target.
+        val jvmLikeTargetCount = kotlinExtension.targets.count {
+            it.platformType == KotlinPlatformType.jvm || it.platformType == KotlinPlatformType.androidJvm
+        }
+        val apiDirName = if (jvmLikeTargetCount == 1) "api" else "api/android"
+        val dumpFileName = "$name.api"
+        val referenceApiFile = layout.projectDirectory.file("$apiDirName/$dumpFileName")
+
+        val androidApiBuild = tasks.register<KotlinApiBuildTask>("androidApiBuild") {
+            description = "Builds Kotlin API for 'main' compilations of ${project.name}. " +
+                "Complementary task and shouldn't be called manually"
+            inputClassesDirs.from(androidMainCompilation.output.classesDirs)
+            outputApiFile.set(layout.buildDirectory.file("$apiDirName/$dumpFileName"))
+            runtimeClasspath.from(configurations.named("bcv-rt-jvm-cp-resolver"))
+        }
+
+        val androidApiCheck = tasks.register<KotlinApiCompareTask>("androidApiCheck") {
+            group = "verification"
+            description = "Checks signatures of public API against the golden value in API folder for ${project.name}"
+            projectApiFile.set(referenceApiFile)
+            generatedApiFile.set(androidApiBuild.flatMap { it.outputApiFile })
+        }
+
+        val androidApiDump = tasks.register("androidApiDump") {
+            group = "other"
+            description = "Syncs the API file for ${project.name}"
+            val generatedApiFile = androidApiBuild.flatMap { it.outputApiFile }
+            inputs.file(generatedApiFile)
+            outputs.file(referenceApiFile)
+            doLast {
+                val target = referenceApiFile.asFile
+                target.parentFile.mkdirs()
+                generatedApiFile.get().asFile.copyTo(target, overwrite = true)
+            }
+        }
+
+        tasks.named("apiCheck") { dependsOn(androidApiCheck) }
+        tasks.named("apiDump") { dependsOn(androidApiDump) }
+    }
+}