Add native OSGi bundle metadata to published jars

Wire the bnd Gradle plugin into the shared otel.java-conventions plugin
so the semconv and semconv-incubating jars are published with OSGi
manifest headers (Bundle-SymbolicName, Export-Package, Import-Package).
This lets the artifacts be consumed directly in OSGi containers without
external re-wrapping.

Fixes #494

Author: royteeuwen

buildSrc/build.gradle.kts

@@ -9,6 +9,7 @@ repositories {
 }
 
 dependencies {
+  implementation("biz.aQute.bnd:biz.aQute.bnd.gradle:7.3.0")
   implementation("com.diffplug.spotless:spotless-plugin-gradle:8.8.0")
   implementation("ru.vyarus:gradle-animalsniffer-plugin:2.0.1")
   implementation("me.champeau.gradle:japicmp-gradle-plugin:0.4.6")

buildSrc/src/main/kotlin/io/opentelemetry/gradle/OtelJavaExtension.kt

@@ -5,8 +5,15 @@
 
 package io.opentelemetry.gradle
 
+import org.gradle.api.provider.ListProperty
 import org.gradle.api.provider.Property
 
 abstract class OtelJavaExtension {
     abstract val moduleName: Property<String>
+
+    /** Whether to generate OSGi bundle metadata. Enabled by default. */
+    abstract val osgiEnabled: Property<Boolean>
+
+    /** Extra packages imported as optional (resolution:=optional), e.g. compileOnly deps. */
+    abstract val osgiOptionalPackages: ListProperty<String>
 }

buildSrc/src/main/kotlin/otel.java-conventions.gradle.kts

@@ -8,10 +8,13 @@ plugins {
   eclipse
   idea
 
+  id("biz.aQute.bnd.builder")
   id("otel.spotless-conventions")
 }
 
 val otelJava = extensions.create<OtelJavaExtension>("otelJava")
+otelJava.osgiEnabled.convention(true)
+otelJava.osgiOptionalPackages.convention(emptyList())
 
 java {
   toolchain {
@@ -29,6 +32,13 @@ checkstyle {
   configProperties["rootDir"] = rootDir
 }
 
+// normalize timestamps and file ordering in jars, making the outputs (including OSGi
+// manifests) reproducible. see open-telemetry/opentelemetry-java#4488
+tasks.withType<AbstractArchiveTask>().configureEach {
+  isPreserveFileTimestamps = false
+  isReproducibleFileOrder = true
+}
+
 val testJavaVersion = gradle.startParameter.projectProperties.get("testJavaVersion")?.let(JavaVersion::toVersion)
 
 tasks {
@@ -85,6 +95,30 @@ tasks {
     }
   }
 
+  afterEvaluate {
+    if (otelJava.osgiEnabled.get()) {
+      named<Jar>("jar") {
+        // Configure OSGi metadata. semconv has no SPI / ServiceLoader needs, so this is the
+        // trimmed form of opentelemetry-java's otel.java-conventions OSGi config.
+        bundle {
+          // Modules may declare optional imports (typically compileOnly deps). The trailing
+          // "*" lets BND auto-import everything else (e.g. io.opentelemetry.api.*).
+          val optionalPackages = otelJava.osgiOptionalPackages.get()
+          val optionalImports =
+            optionalPackages.joinToString(",") { "$it.*;resolution:=optional;version=\"\${@}\"" }
+          val importPackages = if (optionalImports.isEmpty()) "*" else "$optionalImports,*"
+
+          bnd(
+            mapOf(
+              "-exportcontents" to "io.opentelemetry.*",
+              "Import-Package" to importPackages,
+            ),
+          )
+        }
+      }
+    }
+  }
+
   withType<Jar>().configureEach {
     inputs.property("moduleName", otelJava.moduleName)