Generate class exposing version for libraries (#240)

Author: JonasKunz

buildSrc/src/main/kotlin/elastic-otel.library-packaging-conventions.gradle.kts

@@ -1,3 +1,5 @@
+import java.util.stream.Collectors
+
 plugins {
   `java-library`
   id("elastic-otel.java-conventions")
@@ -15,4 +17,42 @@ tasks {
     }
   }
 
+  // Generates a Java class exposing the project version
+  val generateVersionProviderSource by registering() {
+    val packageName = "co.elastic.otel";
+    val className = kebapToCamelCase(project.name)+"Version";
+
+    val outputDir = layout.buildDirectory.dir("generated/version-provider-source")
+    outputs.dir(outputDir)
+    doLast {
+      val packageDir = outputDir.get().asFile.resolve(packageName.replace('.', '/'))
+      packageDir.mkdirs()
+      val source = """
+        package $packageName;
+        
+        /**
+         * This class is generated.
+        */
+        public class $className {
+          public static final String VERSION = "${project.version}";
+        }
+      """.trimIndent()
+      packageDir.resolve("$className.java").writeText(source)
+    }
+  }
+}
+
+sourceSets {
+  main {
+    java {
+      srcDir(tasks.getByName("generateVersionProviderSource"));
+    }
+  }
+}
+
+fun kebapToCamelCase(name : String) : String {
+  val words = name.split("-");
+  return words.stream()
+    .map { w -> Character.toUpperCase(w[0]) + w.substring(1) }
+    .collect(Collectors.joining())
 }

inferred-spans/build.gradle.kts

@@ -37,15 +37,6 @@ tasks.javadoc {
   options.encoding = "UTF-8"
 }
 
-tasks.processResources {
-  doLast {
-    val resourcesDir = sourceSets.main.get().output.resourcesDir
-    val packageDir = resourcesDir!!.resolve("co/elastic/otel/profiler");
-    packageDir.mkdirs();
-    packageDir.resolve("inferred-spans-version.txt").writeText(project.version.toString())
-  }
-}
-
 tasks.withType<Test>().all {
   jvmArgs("-Djava.util.logging.config.file="+sourceSets.test.get().output.resourcesDir+"/logging.properties")
 }

inferred-spans/src/main/java/co/elastic/otel/profiler/InferredSpansProcessor.java

@@ -18,6 +18,7 @@
  */
 package co.elastic.otel.profiler;
 
+import co.elastic.otel.InferredSpansVersion;
 import co.elastic.otel.common.util.ExecutorUtils;
 import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.api.trace.Tracer;
@@ -27,11 +28,7 @@
 import io.opentelemetry.sdk.trace.ReadWriteSpan;
 import io.opentelemetry.sdk.trace.ReadableSpan;
 import io.opentelemetry.sdk.trace.SpanProcessor;
-import java.io.BufferedReader;
 import java.io.File;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;
 import java.util.logging.Level;
@@ -44,8 +41,6 @@ public class InferredSpansProcessor implements SpanProcessor {
 
   public static final String TRACER_NAME = "elastic-inferred-spans";
 
-  private static final String TRACER_VERSION = readInferredSpansVersion();
-
   // Visible for testing
   final SamplingProfiler profiler;
 
@@ -72,7 +67,7 @@ public static InferredSpansProcessorBuilder builder() {
    *     lazily.
    */
   public synchronized void setTracerProvider(TracerProvider provider) {
-    tracer = provider.get(TRACER_NAME, TRACER_VERSION);
+    tracer = provider.get(TRACER_NAME, InferredSpansVersion.VERSION);
   }
 
   @Override
@@ -122,13 +117,4 @@ private Tracer getTracer() {
     }
     return tracer;
   }
-
-  private static String readInferredSpansVersion() {
-    try (InputStream is =
-        InferredSpansProcessor.class.getResourceAsStream("inferred-spans-version.txt")) {
-      return new BufferedReader(new InputStreamReader(is)).readLine();
-    } catch (IOException e) {
-      throw new IllegalStateException("Failed to read version", e);
-    }
-  }
 }