Collect BOM constraints automatically (#1269)

* Collect BOM constraints automatically

Closes: #1121

* Publish assetfilesystem

Author: squarejesse

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

@@ -0,0 +1,55 @@
+import java.util.Locale
+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.KotlinMultiplatformExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinAndroidPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinJsPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinMultiplatformPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
+import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinMetadataTarget
+import org.jetbrains.kotlin.gradle.targets.js.KotlinJsTarget
+
+/**
+ * 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<KotlinAndroidPluginWrapper> {
+        bomConstraints.api(subproject)
+      }
+
+      subproject.plugins.withType<KotlinJsPluginWrapper> {
+        bomConstraints.api(subproject)
+      }
+
+      subproject.plugins.withType<KotlinMultiplatformPluginWrapper> {
+        subproject.extensions.getByType<KotlinMultiplatformExtension>().targets.all {
+          bomConstraints.api(dependencyConstraint(this))
+        }
+      }
+    }
+  }
+}
+
+/** Returns a string like "com.squareup.okio:okio-iosarm64:3.4.0" for this target. */
+private fun Project.dependencyConstraint(target: KotlinTarget): String {
+  val artifactId = when (target) {
+    is KotlinMetadataTarget -> name
+    is KotlinJsTarget -> "$name-js"
+    else -> "$name-${target.targetName.toLowerCase(Locale.ROOT)}"
+  }
+  return "$group:$artifactId:$version"
+}
+
+private fun DependencyConstraintHandler.api(constraintNotation: Any) =
+  add("api", constraintNotation)

okio-assetfilesystem/build.gradle.kts

@@ -1,5 +1,4 @@
-import com.vanniktech.maven.publish.JavadocJar.Dokka
-import com.vanniktech.maven.publish.KotlinMultiplatform
+import com.vanniktech.maven.publish.AndroidSingleVariantLibrary
 import com.vanniktech.maven.publish.MavenPublishBaseExtension
 
 plugins {
@@ -32,6 +31,6 @@ dependencies {
 
 configure<MavenPublishBaseExtension> {
   configure(
-    KotlinMultiplatform(javadocJar = Dokka("dokkaGfm"))
+    AndroidSingleVariantLibrary()
   )
 }

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) {