fix things again

Author: SylvainJuge

Diff for: javaagent-tooling/javaagent-tooling-java9/src/main/java/io/opentelemetry/javaagent/tooling/Java9LambdaClassFileTransformer.java

@@ -9,10 +9,10 @@
 import java.lang.instrument.IllegalClassFormatException;
 import java.security.ProtectionDomain;
 
-/** {@link ClassFileTransformer} implementation that provides java9 jpms module compatibility */
+/** {@link ClassFileTransformer} for lambda instrumentation with java9 jpms module compatibility */
 public class Java9LambdaClassFileTransformer implements ClassFileTransformer {
 
-  private ClassFileTransformer delegate;
+  private final ClassFileTransformer delegate;
 
   public Java9LambdaClassFileTransformer(ClassFileTransformer delegate) {
     this.delegate = delegate;
@@ -27,7 +27,12 @@ public byte[] transform(
       byte[] classfileBuffer)
       throws IllegalClassFormatException {
 
-    Module module = targetClass != null ? targetClass.getModule() : null;
+    if (targetClass == null) {
+      // we expect the target class argument to be non-null, however it's only used to resolve
+      // the JPMS module
+      throw new IllegalStateException("can't resolve module without class");
+    }
+    Module module = targetClass.getModule();
 
     // lambda instrumentation happens only when the lambda is defined, thus the classBeingRedefined
     // must be null otherwise we get a partial instrumentation, for example virtual fields are not

Diff for: javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/AgentInstaller.java

@@ -203,6 +203,9 @@ private static void installBytebuddyAgent(
     if (JavaModule.isSupported()) {
       // wrapping in a JPMS compliant implementation
       transformer = new Java9LambdaClassFileTransformer(transformer);
+    } else {
+      // wrapping in a java 8 compliant transformer
+      transformer = new LambdaClassFileTransformer(transformer);
     }
     ClassFileTransformerHolder.setLambdaClassFileTransformer(transformer);
 

Diff for: javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/LambdaClassFileTransformer.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling;
+
+import java.lang.instrument.ClassFileTransformer;
+import java.lang.instrument.IllegalClassFormatException;
+import java.security.ProtectionDomain;
+
+/** {@link ClassFileTransformer} for lambda instrumentation without jpms modules */
+public class LambdaClassFileTransformer implements ClassFileTransformer {
+
+  private final ClassFileTransformer delegate;
+
+  public LambdaClassFileTransformer(ClassFileTransformer delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override
+  public byte[] transform(
+      ClassLoader loader,
+      String className,
+      Class<?> classBeingRedefined,
+      ProtectionDomain protectionDomain,
+      byte[] classfileBuffer)
+      throws IllegalClassFormatException {
+
+    // lambda instrumentation happens only when the lambda is defined, thus the classBeingRedefined
+    // must be null otherwise we get a partial instrumentation, for example virtual fields are not
+    // properly applied. This parameter is however used in Java9LambdaClassFileTransformer.
+    return delegate.transform(loader, className, null, null, classfileBuffer);
+  }
+}