More explicit fix

Author: trask

agent/agent-tooling/src/main/java/com/microsoft/applicationinsights/agent/internal/classicsdk/ApplicationInsightsAppenderClassFileTransformer.java

@@ -27,6 +27,20 @@ public class ApplicationInsightsAppenderClassFileTransformer implements ClassFil
       UnshadedSdkPackageName.get() + "/log4j/v2/ApplicationInsightsAppender";
   private static final String UNSHADED_CLASS_NAME_LOG_4_JV_1_2 =
       UnshadedSdkPackageName.get() + "/log4j/v1_2/ApplicationInsightsAppender";
+  private static final String UNSHADED_DESCRIPTOR_LOGBACK =
+      methodDescriptor("ch/qos/", "logback/classic/spi/ILoggingEvent");
+  private static final String UNSHADED_DESCRIPTOR_LOG_4_JV_2 =
+      methodDescriptor("org/apache/logging/log4j/core/LogEvent");
+  private static final String UNSHADED_DESCRIPTOR_LOG_4_JV_1_2 =
+      methodDescriptor("org/apache/log4j/spi/LoggingEvent");
+
+  private static String methodDescriptor(String parameterClassName) {
+    return "(L" + parameterClassName + ";)V";
+  }
+
+  private static String methodDescriptor(String firstPart, String secondPart) {
+    return methodDescriptor(firstPart + secondPart);
+  }
 
   @Override
   @Nullable
@@ -72,10 +86,11 @@ public MethodVisitor visitMethod(
         @Nullable String signature,
         @Nullable String[] exceptions) {
       MethodVisitor mv = cw.visitMethod(access, name, descriptor, signature, exceptions);
-      // match append(SomeLoggingEvent): the descriptor type-strings are not checked here
-      // because Shadow relocates the "ch/qos/logback" literal, breaking the match at runtime;
-      // class-name filtering in transform() already guarantees we are in the right class
-      if (name.equals("append") && descriptor.startsWith("(L") && descriptor.endsWith(";)V")) {
+      // Build the logback descriptor at runtime so Shadow cannot relocate the string literal.
+      if (name.equals("append")
+          && (descriptor.equals(UNSHADED_DESCRIPTOR_LOGBACK)
+              || descriptor.equals(UNSHADED_DESCRIPTOR_LOG_4_JV_1_2)
+              || descriptor.equals(UNSHADED_DESCRIPTOR_LOG_4_JV_2))) {
         // no-op the append() method
         mv.visitCode();
         mv.visitInsn(RETURN);