Relocate dependencies in the generated shadowJar (GoogleCloudPlatform#212)

* Add gradle task to relocate dependencies in shaded JAR

* Prevent conscrypt shading

* Prevent accidental shading for source classes

For some reason shadow plugin shades the source classes as well, this
should not be the case. In order to prevent this accidental shading of
source classes, we relocate the source classes back the original package
to exclude them from automatic relocation.

Author: psx95

build.gradle

@@ -88,7 +88,7 @@ subprojects {
 		groovyGradle {
 			target '*.gradle' // default target of groovyGradle
 			greclipse()
-			licenseHeaderFile rootProject.file('buildscripts/spotless.license.gradle'), '(plugins|description)'
+			licenseHeaderFile rootProject.file('buildscripts/spotless.license.gradle'), '(import|plugins|description)'
 		}
 	}
 

exporters/auto/build.gradle

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+import com.github.jengelman.gradle.plugins.shadow.relocation.SimpleRelocator
 plugins {
 	id "maven-publish"
 	id "com.github.johnrengelman.shadow"
@@ -41,10 +42,27 @@ dependencies {
 	}
 }
 
-
 shadowJar {
+	// gradle warns since explicit or implicit dependency on this shadowJar is not declared
+	dependsOn ':shared-resourcemapping:shadowJar'
 	archiveClassifier.set('shaded')
-	mergeServiceFiles()
+	// since we relocate source classes back to their original package, we do not want the SPIs to be re-written for relocated package
+	mergeServiceFiles {
+		exclude "META-INF/services/io.opentelemetry.sdk.autoconfigure.spi.metrics.ConfigurableMetricExporterProvider"
+		exclude "META-INF/services/io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSpanExporterProvider"
+	}
+}
+
+// Auto relocation for all dependencies
+tasks.named('shadowJar') {
+	// Prevent 'conscrypt' from being relocated.
+	// See https://github.com/GoogleCloudPlatform/opentelemetry-operations-java/issues/161#issuecomment-1478831626 for details
+	// Relocating it back to its original location excludes the package from being automatically relocated to the specified prefix
+	relocate new SimpleRelocator("org.conscrypt", "org.conscrypt", new ArrayList<String>(), new ArrayList<String>())
+	relocate new SimpleRelocator("com.google.cloud.opentelemetry.auto", "com.google.cloud.opentelemetry.auto", new ArrayList<String>(), new ArrayList<String>())
+
+	enableRelocation true
+	relocationPrefix 'shadow'
 }
 
 publishing {
@@ -58,4 +76,4 @@ publishing {
 			}
 		}
 	}
-}
+}