"Cannot resolve type description" when class is not present

Hi!

We received a bug report in BlockHound ( https://github.com/reactor/BlockHound/issues/71 ) that looks more like a bug in ByteBuddy.

I was able to reproduce it with the following setup:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
        <version>2.2.1.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>net.bytebuddy</groupId>
        <artifactId>byte-buddy</artifactId>
        <version>1.10.2</version>
    </dependency>

    <dependency>
        <groupId>net.bytebuddy</groupId>
        <artifactId>byte-buddy-agent</artifactId>
        <version>1.10.2</version>
    </dependency>
</dependencies>

public static void main(String[] args) throws Exception {
    Instrumentation instrumentation = ByteBuddyAgent.install();

    String testClass = "ch.qos.logback.classic.Logger";

    new AgentBuilder.Default()
            .with(RedefinitionStrategy.RETRANSFORMATION)
            .with(InitializationStrategy.NoOp.INSTANCE)
            .with((PoolStrategy) (classFileLocator, classLoader) -> new TypePool.Default(
                    new CacheProvider.Simple(),
                    classFileLocator,
                    TypePool.Default.ReaderMode.FAST
            ))
            .with(AgentBuilder.Listener.StreamWriting.toSystemError().withErrorsOnly())

            .type(it -> testClass.equals(it.getName()))
            .transform((builder, typeDescription, classLoader, javaModule) -> {
                return builder.visit(Advice.to(TestAdvice.class).on(named("callAppenders")));
            })
            .installOn(instrumentation);

    Class.forName(testClass);
}

public static class TestAdvice {
    @Advice.OnMethodEnter
    public static void onEnter() {
    }
}

It fails with this exception:

java.lang.IllegalStateException: Cannot resolve type description for org.slf4j.event.LoggingEvent

	at net.bytebuddy.pool.TypePool$Resolution$Illegal.resolve(TypePool.java:159)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$TokenizedGenericType.toErasure(TypePool.java:6241)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType.of(TypePool.java:3412)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType$LazyRawAnnotatedTypeList.get(TypePool.java:3511)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType$LazyRawAnnotatedTypeList.get(TypePool.java:3456)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$LazyMethodDescription$LazyParameterDescription.getType(TypePool.java:6994)
	at net.bytebuddy.description.method.ParameterDescription$AbstractBase.asToken(ParameterDescription.java:178)
	at net.bytebuddy.description.method.ParameterDescription$AbstractBase.asToken(ParameterDescription.java:128)
	at net.bytebuddy.description.method.ParameterList$AbstractBase.asTokenList(ParameterList.java:98)
	at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:825)
	at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:376)
	at net.bytebuddy.description.method.MethodList$AbstractBase.asTokenList(MethodList.java:70)
	at net.bytebuddy.dynamic.scaffold.InstrumentedType$Factory$Default$1.represent(InstrumentedType.java:364)
	at net.bytebuddy.ByteBuddy.rebase(ByteBuddy.java:851)
	at net.bytebuddy.agent.builder.AgentBuilder$TypeStrategy$Default$1.builder(AgentBuilder.java:2007)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$Transformation$Simple$Resolution.apply(AgentBuilder.java:10117)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doTransform(AgentBuilder.java:10494)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10457)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.access$1500(AgentBuilder.java:10223)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$Java9CapableVmDispatcher.run(AgentBuilder.java:10907)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$Java9CapableVmDispatcher.run(AgentBuilder.java:10845)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10413)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$ByteBuddy$ModuleSupport.transform(Unknown Source)
	at java.instrument/sun.instrument.TransformerManager.transform(TransformerManager.java:188)
	at java.instrument/sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:563)
	at java.base/java.lang.ClassLoader.defineClass1(Native Method)
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
	at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
	at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:802)
	at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:700)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:623)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:315)
	at reactor.SampleReactor.main(SampleReactor.java:39)

[raphw]

It’s less a bug than it’s a feature. “Optional types” is something several developers assume for the JVM to work due to it’s implicit type resolution but for legally transforming a type, all signature type information needs to be available during instrumentation.

Byte Buddy requires all type information for a transformed type to be available but for ch.qos.logback.classic.Logger, it cannot find org.slf4j.event.LoggingEvent. It is the equivalent exception to:

Class.forName("ch.qos.logback.classic.Logger").getDeclaredMethods()

Introspection only works if the introspected types are available. The good news is that this does not break anything but only aborts the instrumentation of the incomplete type.

[raphw]

I assume the question is answered, therefore I am closing this.