Performance degradation during JUnit tests

[ptziegler]

Looking at e.g. https://github.com/eclipse-windowbuilder/windowbuilder/actions/runs/22973014954/job/66694479658?pr=1394, tests tend to take up to an hour on Windows. A few years ago, this used to be ~40-50min max. Something is consuming a lot of time.

[ptziegler]

I'm suspecting our CompositeClassLoader as one of the big culprits. Each test takes ~1s out of which 300ms are spent on (trying to) load classes.

Misses are especially expensive because we have to iterate over all class-loaders. Perhaps in addition to a whitelist, we should also keep track of all classes a class-loader CAN'T load?

[ptziegler]

This is another hotspot. The enhanced class can NEVER be loaded, so we'll always go through the whole class-loader list.

windowbuilder/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/model/creation/ThisCreationSupport.java

Lines 406 to 416 in 7bf365b

	private void createEnhancer(Class<?> componentClass, final ExecutionFlowFrameVisitor visitor) {
	final TypeCache.SimpleKey proxyKey = new TypeCache.SimpleKey(componentClass);
	DynamicType.Builder<?> builder = new ByteBuddy()
	.subclass(componentClass) //
	.defineField(MethodInterceptor.FIELD_INTERCEPTOR, MethodInterceptor.class, Modifier.PRIVATE)
	.method(ElementMatchers.noneOf(getIgnoredMethods(componentClass))) //
	.intercept(MethodDelegation.to(new StubMethodInterceptor(), MethodInterceptor.class));
	PROXY_CACHE.findOrInsert(getClassLoader(), proxyKey, () -> builder.make().load(getClassLoader()).getLoaded());
	}

Perhaps we can fail early by checking against ReflectionUtils.isEnhancedClass()?