Add Dependency Injection Support for WorldGen Plugins

[spookynutz]

Hello,

I'm opening this PR to work on the implementation of dependency injection for the WorldGen Plugins.
This PR is opened as a draft as a base for discussion since I'm new to the code and don't quite understand how things work yet.

Contains

Implementation for proposal in #5003

[spookynutz]

My main interrogation was where this manager should be used. My assumption from what I found was to replace this here :

Terasology/engine/src/main/java/org/terasology/engine/core/modes/loadProcesses/InitialiseWorld.java

Lines 85 to 86 in ae83461

	ModuleEnvironment environment = context.get(ModuleManager.class).getEnvironment();
	context.put(WorldGeneratorPluginLibrary.class, new DefaultWorldGeneratorPluginLibrary(environment, context));

Could anyone confirm this ?

[BenjaminAmos]

Although, I am wondering if it would be easier to implement this by just calling InjectionManager.inject(item) in DefaultWorldGeneratorPluginLibrary#instantiateAllOfType:

Terasology/engine/src/main/java/org/terasology/engine/world/generator/plugin/DefaultWorldGeneratorPluginLibrary.java

Lines 31 to 45 in ae83461

	@Override
	public <U extends WorldGeneratorPlugin> List<U> instantiateAllOfType(Class<U> ofType) {
	List<U> result = Lists.newArrayList();
	for (ClassMetadata<?, ?> classMetadata : library) {
	if (ofType.isAssignableFrom(classMetadata.getType())
	&& classMetadata.isConstructable()
	&& classMetadata.getType().getAnnotation(RegisterPlugin.class) != null) {
	U item = ofType.cast(classMetadata.newInstance());
	if (item != null) {
	result.add(item);
	}
	}
	}
	return result;
	}

[jdrueckert]

@spookynutz Did the review comments help or are you still blocked somehow? Are you planning to continue with this?

[spookynutz]

Although, I am wondering if it would be easier to implement this by just calling InjectionManager.inject(item) in DefaultWorldGeneratorPluginLibrary#instantiateAllOfType:

Terasology/engine/src/main/java/org/terasology/engine/world/generator/plugin/DefaultWorldGeneratorPluginLibrary.java

Lines 31 to 45 in ae83461

	@Override
	public <U extends WorldGeneratorPlugin> List<U> instantiateAllOfType(Class<U> ofType) {
	List<U> result = Lists.newArrayList();
	for (ClassMetadata<?, ?> classMetadata : library) {
	if (ofType.isAssignableFrom(classMetadata.getType())
	&& classMetadata.isConstructable()
	&& classMetadata.getType().getAnnotation(RegisterPlugin.class) != null) {
	U item = ofType.cast(classMetadata.newInstance());
	if (item != null) {
	result.add(item);
	}
	}
	}
	return result;
	}

Hello @BenjaminAmos, @jdrueckert, sorry for the delayed response I got taken by work and did not have time to advance the issue ...
I'm not sure I understand correctly this comment. Are you suggesting to drop the creation of WorldGeneratorPluginManager and to rather use

Terasology/engine/src/main/java/org/terasology/engine/registry/InjectionHelper.java

Line 37 in 33dabf5

public static <T> T inject(final T object, Context context) {

around

Terasology/engine/src/main/java/org/terasology/engine/world/generator/plugin/DefaultWorldGeneratorPluginLibrary.java

Line 40 in 33dabf5

result.add(item);

?

[BenjaminAmos]

Are you suggesting to drop the creation of WorldGeneratorPluginManager and to rather use

Terasology/engine/src/main/java/org/terasology/engine/registry/InjectionHelper.java

Line 37 in 33dabf5

public static <T> T inject(final T object, Context context) {

around

Terasology/engine/src/main/java/org/terasology/engine/world/generator/plugin/DefaultWorldGeneratorPluginLibrary.java

Line 40 in 33dabf5

result.add(item);

Yes, that is essentially what I think I meant (it was a while ago now). Although the current code is rather guilty of this already, I would prefer that new code does not introduce unecessary abstractions (the less code the better, prioritising readability).