Externally observed LinkageError when compiling a custom renderer in an NSF

[jesse-gallagher]

The error is in the format:

2021-11-24T08:56:24.7750152Z [ERROR] Caused by: java.lang.LinkageError: loading constraint violation when overriding method "com/ibm/xsp/renderkit/html_basic/MessagesRendererEx.encodeBegin(Ljavax/faces/context/FacesContext;Ljavax/faces/component/UIComponent;)V" during creation of class "someapp/theme/renderkit/MessagesRenderer": loader "com/ibm/xsp/extlib/javacompiler/JavaSourceClassLoader@29c12712" of class "someapp/theme/renderkit/MessagesRenderer" and loader "java/net/URLClassLoader@f4f6dc2" of class "com/ibm/xsp/renderkit/html_basic/MessagesRendererEx" have different types for the method signature
2021-11-24T10:12:42.0343022Z [INFO] 	at java.lang.ClassLoader.defineClassImpl(Native Method)
2021-11-24T10:12:42.0343723Z [INFO] 	at java.lang.ClassLoader.defineClassInternal(ClassLoader.java:398)
2021-11-24T10:12:42.0344374Z [INFO] 	at java.lang.ClassLoader.defineClass(ClassLoader.java:359)
2021-11-24T10:12:42.0345039Z [INFO] 	at java.lang.ClassLoader.defineClass(ClassLoader.java:314)
2021-11-24T10:12:42.0345765Z [INFO] 	at com.ibm.xsp.extlib.javacompiler.JavaSourceClassLoader.lambda$2(JavaSourceClassLoader.java:161)
2021-11-24T10:12:42.0348037Z [INFO] 	at com.ibm.xsp.extlib.javacompiler.JavaSourceClassLoader$$Lambda$114/0x000000004c9b5910.apply(Unknown Source)
2021-11-24T10:12:42.0367898Z [INFO] 	at java.util.HashMap.computeIfAbsent(HashMap.java:1127)
2021-11-24T10:12:42.0368756Z [INFO] 	at com.ibm.xsp.extlib.javacompiler.JavaSourceClassLoader.findClass(JavaSourceClassLoader.java:150)
2021-11-24T10:12:42.0369517Z [INFO] 	at java.lang.ClassLoader.loadClassHelper(ClassLoader.java:953)
2021-11-24T10:12:42.0370264Z [INFO] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:898)
2021-11-24T10:12:42.0370928Z [INFO] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:881)
2021-11-24T10:12:42.0371777Z [INFO] 	at com.ibm.xsp.extlib.javacompiler.JavaSourceClassLoader.addClasses(JavaSourceClassLoader.java:247)
2021-11-24T10:12:42.0372422Z [INFO] 	... 11 more

This is initially similar to #231 , but that was specifically about overriding a renderer found in your custom OSGi bundle inside the NSF, while this case doesn't have that intermediate level.

So far, I have not been able to reproduce this locally using a couple versions. It was originally observed when compiling in a Docker container using a build of 3.6.0-SNAPSHOT.

[jesse-gallagher]

This is reproducible locally by also including another class, that one a Converter implementation. I wonder if it's somehow causing trouble by loading XPages core classes from multiple places, or perhaps it's re-loading those classes for each class compilation and considering them different.

[jesse-gallagher]

There isn't anything about the specific implementations of the classes that causes trouble, and they don't need to be registered in faces-config.xml (which makes sense). The mere presence of these two classes in an NSF will cause this:

package org.openntf.nsfodp.example.nsf;

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;

public class FileSizeConverter implements Converter {
	@Override public Object getAsObject(FacesContext arg0, UIComponent arg1, String arg2) {
		return null;
	}
	@Override public String getAsString(FacesContext context, UIComponent component, Object obj) {
		return null;
	}
}

and

package org.openntf.nsfodp.example.nsf;

import java.io.IOException;

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;

import com.ibm.xsp.renderkit.html_basic.MessagesRendererEx;

public class ExampleRenderer extends MessagesRendererEx {
	@Override public void encodeBegin(FacesContext paramFacesContext, UIComponent paramUIComponent) throws IOException {
	}
	@Override public void encodeEnd(FacesContext paramFacesContext, UIComponent paramUIComponent) throws IOException {
	}
}

[jesse-gallagher]

This turned out to be caused by a problem in the Bazaar upstream: the dependency ClassLoader didn't delegate to the CL passed in to the object, and so it would end up pulling classes from the bundles from a different source.