Collect BOM constraints automatically

build-support/src/main/kotlin/bom.kt

@@ -0,0 +1,45 @@
+import org.gradle.api.Project
+import org.gradle.api.artifacts.dsl.DependencyConstraintHandler
+import org.gradle.kotlin.dsl.getByType
+import org.gradle.kotlin.dsl.withType
+import org.jetbrains.kotlin.gradle.dsl.KotlinJsProjectExtension
+import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinJsPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinMultiplatformPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
+
+/**
+ * Collect all the root project's multiplatform targets and add them to the BOM.
+ *
+ * Only published subprojects are included.
+ *
+ * This supports Kotlin/Multiplatform and Kotlin/JS subprojects.
+ */
+fun Project.collectBomConstraints() {
+  val bomConstraints: DependencyConstraintHandler = dependencies.constraints
+  rootProject.subprojects {
+    val subproject = this
+
+    subproject.plugins.withId("com.vanniktech.maven.publish.base") {
+      subproject.plugins.withType<KotlinMultiplatformPluginWrapper> {
+        bomConstraints.api(subproject)
+        subproject.extensions.getByType<KotlinMultiplatformExtension>().targets.all {
+          bomConstraints.api(dependencyConstraint(this))
+        }
+      }
+
+      subproject.plugins.withType<KotlinJsPluginWrapper> {
+        bomConstraints.api(subproject)
+        bomConstraints.api(
+          dependencyConstraint(subproject.extensions.getByType<KotlinJsProjectExtension>().js())
+        )
+      }
+    }
+  }
+}
+
+private fun Project.dependencyConstraint(target: KotlinTarget) =
+  "$group:$name-${target.targetName}:$version"
+
+private fun DependencyConstraintHandler.api(constraintNotation: Any) =
+  add("api", constraintNotation)

okio-bom/build.gradle.kts

@@ -3,16 +3,7 @@ plugins {
   id("java-platform")
 }
 
-dependencies {
-  constraints {
-    api(projects.okio)
-    api(projects.okioFakefilesystem)
-    if (kmpJsEnabled) {
-      // No typesafe project accessor as the accessor won't exist if kmpJs is not enabled.
-      api(project(":okio-nodefilesystem"))
-    }
-  }
-}
+collectBomConstraints()
 
 extensions.configure<PublishingExtension> {
   publications.create("maven", MavenPublication::class) {