Add NullAway null-safety annotations to javaagent-tooling and javaagent modules

Part of #15991

Enables NullAway for javaagent-tooling, javaagent-tooling-java9, and javaagent
modules, and adds required @nullable annotations to AgentInstaller,
AgentStarterImpl, DefineClassHandler, ExtensionClassLoader,
InputStreamUrlConnection, OpenTelemetryInstaller, RemappingUrlConnection,
SafeServiceLoader, Utils, ConfigurationFile,
JavaagentDistributionAccessCustomizerProvider,
FieldBackedImplementationInstaller, VirtualFieldImplementationsGenerator,
InstrumentationLoader, InstrumentationModuleInstaller, MuzzleMatcher,
RegexUrlTemplateCustomizerInitializer, IndyBootstrap,
InstrumentationModuleClassLoader, ClassLoaderMap, ClassLoaderValue, Trie,
and TrieImpl.

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

javaagent-tooling/build.gradle.kts

@@ -2,6 +2,7 @@ import net.ltgt.gradle.errorprone.errorprone
 
 plugins {
   id("otel.java-conventions")
+  id("otel.nullaway-conventions")
   id("otel.publish-conventions")
   id("otel.jmh-conventions")
 }

javaagent-tooling/javaagent-tooling-java9/build.gradle.kts

@@ -1,5 +1,6 @@
 plugins {
   id("otel.java-conventions")
+  id("otel.nullaway-conventions")
   id("otel.publish-conventions")
 }
 

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/AgentInstaller.java

@@ -10,6 +10,7 @@
 import static io.opentelemetry.javaagent.tooling.SafeServiceLoader.loadOrdered;
 import static io.opentelemetry.javaagent.tooling.Utils.getResourceName;
 import static java.util.Collections.emptyList;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.SEVERE;
 import static net.bytebuddy.matcher.ElementMatchers.any;
@@ -153,7 +154,9 @@ private static void installBytebuddyAgent(
     AutoConfiguredOpenTelemetrySdk autoConfiguredSdk =
         installOpenTelemetrySdk(extensionClassLoader);
 
-    ConfigProperties sdkConfig = AutoConfigureUtil.getConfig(autoConfiguredSdk);
+    ConfigProperties sdkConfig =
+        requireNonNull(
+            AutoConfigureUtil.getConfig(autoConfiguredSdk), "SDK config must not be null");
 
     setBootstrapPackages(sdkConfig, extensionClassLoader);
     ConfiguredResourceAttributesHolder.initialize(
@@ -287,7 +290,7 @@ private static AgentBuilder configureIgnoredTypes(
     IgnoredTypesBuilderImpl builder = new IgnoredTypesBuilderImpl();
     for (IgnoredTypesConfigurer configurer :
         loadOrdered(IgnoredTypesConfigurer.class, extensionClassLoader)) {
-      configurer.configure(builder, config != null ? config : EmptyConfigProperties.INSTANCE);
+      configurer.configure(builder, config);
     }
 
     Trie<Boolean> ignoredTasksTrie = builder.buildIgnoredTasksTrie();

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/AgentStarterImpl.java

@@ -18,6 +18,7 @@
 import java.lang.instrument.UnmodifiableClassException;
 import java.security.ProtectionDomain;
 import java.util.ServiceLoader;
+import javax.annotation.Nullable;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassVisitor;
 import org.objectweb.asm.ClassWriter;
@@ -34,7 +35,7 @@ public class AgentStarterImpl implements AgentStarter {
   private final Instrumentation instrumentation;
   private final File javaagentFile;
   private final boolean isSecurityManagerSupportEnabled;
-  private ClassLoader extensionClassLoader;
+  @Nullable private ClassLoader extensionClassLoader;
 
   public AgentStarterImpl(
       Instrumentation instrumentation,
@@ -142,6 +143,7 @@ private static void logUnrecognizedLoggerImplWarning(String loggerImplementation
             + "'. The agent will use the no-op implementation.");
   }
 
+  @Nullable
   @Override
   public ClassLoader getExtensionClassLoader() {
     return extensionClassLoader;
@@ -156,6 +158,7 @@ private static class LaunchHelperClassFileTransformer implements ClassFileTransf
     boolean hookInserted = false;
     boolean transformed = false;
 
+    @Nullable
     @Override
     public byte[] transform(
         ClassLoader loader,
@@ -202,6 +205,7 @@ public void visitCode() {
   private static class InetAddressClassFileTransformer implements ClassFileTransformer {
     boolean hookInserted = false;
 
+    @Nullable
     @Override
     public byte[] transform(
         ClassLoader loader,

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/DefineClassHandler.java

@@ -11,6 +11,7 @@
 import io.opentelemetry.javaagent.bootstrap.DefineClassHelper.Handler;
 import java.util.HashSet;
 import java.util.Set;
+import javax.annotation.Nullable;
 import org.objectweb.asm.ClassReader;
 
 public class DefineClassHandler implements Handler {
@@ -27,7 +28,7 @@ public DefineClassContext beforeDefineClass(
     if (classBytes == null
         || (classBytes.length == 40
             && new String(classBytes, ISO_8859_1).startsWith("J9ROMCLASSCOOKIE"))) {
-      return null;
+      return DefineClassContextImpl.NOP;
     }
 
     Set<String> superNames = new HashSet<>();
@@ -85,9 +86,7 @@ private static void addSuperNames(Set<String> superNames, Class<?> clazz) {
 
   @Override
   public void afterDefineClass(DefineClassContext context) {
-    if (context != null) {
-      context.exit();
-    }
+    context.exit();
   }
 
   /**
@@ -109,15 +108,15 @@ public static Set<String> getSuperTypes() {
   private static class DefineClassContextImpl implements DefineClassContext {
     private static final DefineClassContextImpl NOP = new DefineClassContextImpl();
 
-    private final DefineClassContextImpl previous;
-    String failedClassDotName;
-    Set<String> superDotNames;
+    @Nullable private final DefineClassContextImpl previous;
+    @Nullable String failedClassDotName;
+    @Nullable Set<String> superDotNames;
 
     private DefineClassContextImpl() {
       previous = null;
     }
 
-    private DefineClassContextImpl(DefineClassContextImpl previous) {
+    private DefineClassContextImpl(@Nullable DefineClassContextImpl previous) {
       this.previous = previous;
     }
 
@@ -130,7 +129,7 @@ static DefineClassContextImpl enter() {
 
     @Override
     public void exit() {
-      defineClassContext.set(previous);
+      defineClassContext.set(previous != null ? previous : NOP);
     }
   }
 }

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/ExtensionClassLoader.java

@@ -109,7 +109,7 @@ private static void includeEmbeddedExtensionsIfFound(List<URL> extensions, File
     }
   }
 
-  private static File ensureTempDirectoryExists(File tempDirectory) throws IOException {
+  private static File ensureTempDirectoryExists(@Nullable File tempDirectory) throws IOException {
     if (tempDirectory == null) {
       tempDirectory = Files.createTempDirectory("otel-extensions").toFile();
       tempDirectory.deleteOnExit();

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/InputStreamUrlConnection.java

@@ -9,6 +9,7 @@
 import java.net.URL;
 import java.net.URLConnection;
 import java.security.Permission;
+import javax.annotation.Nullable;
 
 public class InputStreamUrlConnection extends URLConnection {
   private final InputStream inputStream;
@@ -30,6 +31,7 @@ public InputStream getInputStream() {
     return inputStream;
   }
 
+  @Nullable
   @Override
   public Permission getPermission() {
     // No permissions needed because all classes are in memory

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/OpenTelemetryInstaller.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.javaagent.tooling;
 
 import static java.util.Arrays.asList;
+import static java.util.Collections.emptyMap;
 
 import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.instrumentation.config.bridge.ConfigPropertiesBackedConfigProvider;
@@ -16,6 +17,7 @@
 import io.opentelemetry.sdk.autoconfigure.SdkAutoconfigureAccess;
 import io.opentelemetry.sdk.autoconfigure.internal.AutoConfigureUtil;
 import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 
 public final class OpenTelemetryInstaller {
@@ -36,15 +38,17 @@ public static AutoConfiguredOpenTelemetrySdk installOpenTelemetrySdk(
             .build();
     OpenTelemetrySdk sdk = autoConfiguredSdk.getOpenTelemetrySdk();
     ConfigProperties configProperties = AutoConfigureUtil.getConfig(autoConfiguredSdk);
-    boolean declarativeConfigUsed = configProperties == null;
 
-    if (!declarativeConfigUsed) {
+    if (configProperties != null) {
       // Provide a fake declarative configuration based on config properties
       // so that declarative configuration API can be used everywhere
       sdk =
           new ExtendedOpenTelemetrySdkWrapper(
               sdk, ConfigPropertiesBackedConfigProvider.create(configProperties));
       AgentDistributionConfig.set(AgentDistributionConfig.fromConfigProperties(configProperties));
+    } else {
+      // Declarative config path: no ConfigProperties available, use empty defaults
+      configProperties = DefaultConfigProperties.createFromMap(emptyMap());
     }
 
     setForceFlush(sdk);

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/RemappingUrlConnection.java

@@ -15,6 +15,7 @@
 import java.security.Permission;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
+import javax.annotation.Nullable;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.commons.ClassRemapper;
@@ -50,7 +51,7 @@ public class RemappingUrlConnection extends URLConnection {
   private final JarFile delegateJarFile;
   private final JarEntry entry;
 
-  private byte[] cacheClassBytes;
+  @Nullable private byte[] cacheClassBytes;
 
   public RemappingUrlConnection(URL url, JarFile delegateJarFile, JarEntry entry) {
     super(url);
@@ -89,6 +90,7 @@ private static byte[] remapClassBytes(InputStream in) throws IOException {
     return cw.toByteArray();
   }
 
+  @Nullable
   @Override
   public Permission getPermission() {
     // No permissions needed because all classes are in memory

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/SafeServiceLoader.java

@@ -12,8 +12,10 @@
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.ServiceLoader;
 import java.util.logging.Logger;
+import javax.annotation.Nullable;
 
 public final class SafeServiceLoader {
 
@@ -30,13 +32,14 @@ public final class SafeServiceLoader {
    */
   // Because we want to catch exception per iteration
   @SuppressWarnings("ForEachIterable")
-  public static <T> List<T> load(Class<T> serviceClass, ClassLoader classLoader) {
+  public static <T> List<T> load(Class<T> serviceClass, @Nullable ClassLoader classLoader) {
     List<T> result = new ArrayList<>();
     ServiceLoader<T> services = ServiceLoader.load(serviceClass, classLoader);
     for (Iterator<T> iterator = new SafeIterator<>(services.iterator()); iterator.hasNext(); ) {
-      T service = iterator.next();
-      if (service != null) {
-        result.add(service);
+      try {
+        result.add(iterator.next());
+      } catch (NoSuchElementException ignored) {
+        // UnsupportedClassVersionError was thrown and handled by SafeIterator
       }
     }
     return result;
@@ -47,7 +50,7 @@ public static <T> List<T> load(Class<T> serviceClass, ClassLoader classLoader) {
    * comparing their {@link Ordered#order()}.
    */
   public static <T extends Ordered> List<T> loadOrdered(
-      Class<T> serviceClass, ClassLoader classLoader) {
+      Class<T> serviceClass, @Nullable ClassLoader classLoader) {
     List<T> result = load(serviceClass, classLoader);
     result.sort(Comparator.comparing(Ordered::order));
     return result;
@@ -89,7 +92,7 @@ public T next() {
         return delegate.next();
       } catch (UnsupportedClassVersionError unsupportedClassVersionError) {
         handleUnsupportedClassVersionError(unsupportedClassVersionError);
-        return null;
+        throw new NoSuchElementException(unsupportedClassVersionError.getMessage());
       }
     }
   }