Remove generated InstrumentationModule#getMuzzleReferences() method from the source code

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/instrumentation/InstrumentationModule.java

@@ -10,7 +10,6 @@
 
 import io.opentelemetry.instrumentation.api.config.Config;
 import io.opentelemetry.javaagent.extension.Ordered;
-import io.opentelemetry.javaagent.extension.muzzle.ClassRef;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.LinkedHashSet;
@@ -148,20 +147,6 @@ public ElementMatcher.Junction<ClassLoader> classLoaderMatcher() {
   /** Returns a list of all individual type instrumentation in this module. */
   public abstract List<TypeInstrumentation> typeInstrumentations();
 
-  /**
-   * Returns references to helper and library classes used in this module's type instrumentation
-   * advices, grouped by {@link ClassRef#getClassName()}.
-   *
-   * <p>The actual implementation of this method is generated automatically during compilation by
-   * the {@code io.opentelemetry.instrumentation.javaagent-codegen} Gradle plugin.
-   *
-   * <p><b>This method is generated automatically</b>: if you override it, the muzzle compile plugin
-   * will not generate a new implementation, it will leave the existing one.
-   */
-  public Map<String, ClassRef> getMuzzleReferences() {
-    return Collections.emptyMap();
-  }
-
   /**
    * Returns a list of instrumentation helper classes, automatically detected by muzzle during
    * compilation. Those helpers will be injected into the application classloader.

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/ClassRef.java

@@ -10,15 +10,14 @@
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeMethods;
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeSet;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import java.util.Set;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * Represents a reference to a class used in the instrumentation advice or helper class code (or the
  * helper class itself).
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public final class ClassRef {

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/ClassRefBuilder.java

@@ -8,7 +8,6 @@
 import static java.util.Arrays.asList;
 import static java.util.Collections.emptySet;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.LinkedHashSet;
@@ -20,7 +19,7 @@
 /**
  * The builder of {@link ClassRef}.
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public final class ClassRefBuilder {

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/FieldRef.java

@@ -8,7 +8,6 @@
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeFlags;
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeSet;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import java.util.Set;
 import java.util.stream.Collectors;
 import net.bytebuddy.jar.asm.Type;
@@ -17,7 +16,7 @@
  * Represents a reference to a field used in the instrumentation advice or helper class code. Part
  * of a {@link ClassRef}.
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public final class FieldRef {

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/Flag.java

@@ -5,13 +5,12 @@
 
 package io.opentelemetry.javaagent.extension.muzzle;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import net.bytebuddy.jar.asm.Opcodes;
 
 /**
  * Expected flag (or lack of flag) on a class, method or field reference.
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public interface Flag {

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/MethodRef.java

@@ -8,7 +8,6 @@
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeFlags;
 import static io.opentelemetry.javaagent.extension.muzzle.ReferenceMergeUtil.mergeSet;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -19,7 +18,7 @@
  * Represents a reference to a method used in the instrumentation advice or helper class code. Part
  * of a {@link ClassRef}.
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public final class MethodRef {

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/extension/muzzle/Source.java

@@ -5,13 +5,12 @@
 
 package io.opentelemetry.javaagent.extension.muzzle;
 
-import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import java.util.Objects;
 
 /**
  * Represents the source (file name, line number) of a reference.
  *
- * <p>This class is used in the auto-generated {@link InstrumentationModule#getMuzzleReferences()}
+ * <p>This class is used in the auto-generated {@code InstrumentationModule#getMuzzleReferences()}
  * method, it is not meant to be used directly by agent extension developers.
  */
 public final class Source {

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/instrumentation/InstrumentationModuleInstaller.java

@@ -78,7 +78,7 @@ AgentBuilder install(
 
     ElementMatcher.Junction<ClassLoader> moduleClassLoaderMatcher =
         instrumentationModule.classLoaderMatcher();
-    MuzzleMatcher muzzleMatcher = new MuzzleMatcher(instrumentationModule, helperClassNames);
+    MuzzleMatcher muzzleMatcher = new MuzzleMatcher(instrumentationModule);
     AgentBuilder.Transformer helperInjector =
         new HelperInjector(
             instrumentationModule.instrumentationName(),
@@ -148,14 +148,11 @@ static FieldBackedProvider get(
    */
   private static class MuzzleMatcher implements AgentBuilder.RawMatcher {
     private final InstrumentationModule instrumentationModule;
-    private final List<String> helperClassNames;
     private final AtomicBoolean initialized = new AtomicBoolean(false);
     private volatile ReferenceMatcher referenceMatcher;
 
-    private MuzzleMatcher(
-        InstrumentationModule instrumentationModule, List<String> helperClassNames) {
+    private MuzzleMatcher(InstrumentationModule instrumentationModule) {
       this.instrumentationModule = instrumentationModule;
-      this.helperClassNames = helperClassNames;
     }
 
     @Override
@@ -202,11 +199,7 @@ public boolean matches(
     // during the agent setup
     private ReferenceMatcher getReferenceMatcher() {
       if (initialized.compareAndSet(false, true)) {
-        referenceMatcher =
-            new ReferenceMatcher(
-                helperClassNames,
-                instrumentationModule.getMuzzleReferences(),
-                instrumentationModule::isHelperClass);
+        referenceMatcher = ReferenceMatcher.of(instrumentationModule);
       }
       return referenceMatcher;
     }

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/muzzle/ClassLoaderMatcher.java

@@ -56,11 +56,7 @@ private static List<Mismatch> matches(
 
   private static List<Mismatch> checkReferenceMatcher(
       InstrumentationModule instrumentationModule, ClassLoader classLoader) {
-    ReferenceMatcher muzzle =
-        new ReferenceMatcher(
-            instrumentationModule.getMuzzleHelperClassNames(),
-            instrumentationModule.getMuzzleReferences(),
-            instrumentationModule::isHelperClass);
+    ReferenceMatcher muzzle = ReferenceMatcher.of(instrumentationModule);
     return muzzle.getMismatchedReferenceSources(classLoader);
   }
 

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/muzzle/MuzzleReferencesAccessor.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.muzzle;
+
+import static java.util.Collections.emptyMap;
+
+import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
+import io.opentelemetry.javaagent.extension.muzzle.ClassRef;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.util.Map;
+
+/**
+ * This class is used to access {@code getMuzzleReferences} method from the {@link
+ * InstrumentationModule} class. That method is not visible in the source code and instead is
+ * generated automatically during compilation by the {@code
+ * io.opentelemetry.instrumentation.javaagent-codegen} Gradle plugin.
+ */
+class MuzzleReferencesAccessor {
+  private static final ClassValue<MethodHandle> getMuzzleReferences =
+      new ClassValue<MethodHandle>() {
+        @Override
+        protected MethodHandle computeValue(Class<?> type) {
+          MethodHandles.Lookup lookup = MethodHandles.publicLookup();
+          MethodHandle handle;
+          try {
+            // This method is generated automatically during compilation by
+            // the io.opentelemetry.instrumentation.javaagent-codegen Gradle plugin.
+            handle =
+                lookup.findVirtual(type, "getMuzzleReferences", MethodType.methodType(Map.class));
+          } catch (NoSuchMethodException | IllegalAccessException e) {
+            handle = null;
+          }
+          return handle;
+        }
+      };
+
+  /**
+   * Returns references to helper and library classes used in the given module's type
+   * instrumentation advices, grouped by {@link ClassRef#getClassName()}.
+   */
+  @SuppressWarnings("unchecked")
+  static Map<String, ClassRef> getFor(InstrumentationModule instrumentationModule) {
+    Map<String, ClassRef> muzzleReferences = emptyMap();
+    MethodHandle methodHandle = getMuzzleReferences.get(instrumentationModule.getClass());
+    if (methodHandle != null) {
+      try {
+        muzzleReferences = (Map<String, ClassRef>) methodHandle.invoke(instrumentationModule);
+      } catch (Throwable ignored) {
+        // silence error prone
+      }
+    }
+    return muzzleReferences;
+  }
+}

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/muzzle/ReferenceMatcher.java

@@ -9,6 +9,7 @@
 import static java.util.Collections.singletonList;
 
 import io.opentelemetry.instrumentation.api.caching.Cache;
+import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import io.opentelemetry.javaagent.extension.muzzle.ClassRef;
 import io.opentelemetry.javaagent.extension.muzzle.FieldRef;
 import io.opentelemetry.javaagent.extension.muzzle.Flag;
@@ -36,7 +37,14 @@ public final class ReferenceMatcher {
   private final Set<String> helperClassNames;
   private final InstrumentationClassPredicate instrumentationClassPredicate;
 
-  public ReferenceMatcher(
+  public static ReferenceMatcher of(InstrumentationModule instrumentationModule) {
+    return new ReferenceMatcher(
+        instrumentationModule.getMuzzleHelperClassNames(),
+        MuzzleReferencesAccessor.getFor(instrumentationModule),
+        instrumentationModule::isHelperClass);
+  }
+
+  ReferenceMatcher(
       List<String> helperClassNames,
       Map<String, ClassRef> references,
       Predicate<String> libraryInstrumentationPredicate) {

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/muzzle/ReferencesPrinter.java

@@ -21,15 +21,15 @@ public final class ReferencesPrinter {
 
   /**
    * For all {@link InstrumentationModule}s found in the current thread's context classloader this
-   * method prints references returned by the {@link InstrumentationModule#getMuzzleReferences()}
-   * method to the standard output.
+   * method prints references returned by the {@link
+   * MuzzleReferencesAccessor#getFor(InstrumentationModule)} method to the standard output.
    */
   public static void printMuzzleReferences() {
     for (InstrumentationModule instrumentationModule :
         ServiceLoader.load(InstrumentationModule.class)) {
       try {
         System.out.println(instrumentationModule.getClass().getName());
-        for (ClassRef ref : instrumentationModule.getMuzzleReferences().values()) {
+        for (ClassRef ref : MuzzleReferencesAccessor.getFor(instrumentationModule).values()) {
           System.out.print(prettyPrint(ref));
         }
       } catch (RuntimeException e) {