Add log4j.plugin.enableBndAnnotations option to PluginProcessor

[ppkarwasz]

This adds a log4j.plugin.enableBndAnnotations option to the PluginProcessor. Its default value is inferred from the compiler classpath.

We also rename the pluginPackage option to a more coherent log4j.plugin.package option.

Fixes #3251

[ppkarwasz]

This looks for ServiceConsumer on the plugin processor's classpath, while it should look for it on the application classpath.

[vy]

@ppkarwasz, why do we need a toggle property instead of disabling it, always? This very much smells like leaking an internal detail through configuration properties.

[ppkarwasz]

@ppkarwasz, why do we need a toggle property instead of disabling it, always? This very much smells like leaking an internal detail through configuration properties.

It is an option that controls the output of the PluginProcessor, so I would not call it an internal detail. Should we disable BND annotations by default (for users) and keep the option for our own builds (the BND annotations are useful to generate the necessary META-INF/services files and similar)?

[vy]

Should we disable BND annotations by default (for users) and keep the option for our own builds (the BND annotations are useful to generate the necessary META-INF/services files and similar)?

Could you elaborate on how we can implement this? Does this also mean, there will be no need for a toggle property?

[ppkarwasz]

Should we disable BND annotations by default (for users) and keep the option for our own builds (the BND annotations are useful to generate the necessary META-INF/services files and similar)?

Could you elaborate on how we can implement this? Does this also mean, there will be no need for a toggle property?

What I mean is, I just replace:

logging-log4j2/log4j-plugin-processor/src/main/java/org/apache/logging/log4j/plugin/processor/PluginProcessor.java

Lines 318 to 325 in e6e6ddd

	private static boolean isServiceConsumerClassPresent() {
	try {
	Class.forName("aQute.bnd.annotation.spi.ServiceConsumer");
	return true;
	} catch (ClassNotFoundException e) {
	return false;
	}
	}

with return false and we add -Alog4j.plugin.enabledBndAnnotations=true to our builds. BND runs after compile and it registers the PluginService in the correct files, due to the presence of the @ServiceProvider annotation.