Proper Experiment Registry

src/main/java/ch/njol/skript/Skript.java

@@ -203,8 +203,6 @@ public static void updateMinecraftVersion() {
 
 	@Nullable
 	private static Version version = null;
-	@Deprecated(since = "2.9.0", forRemoval = true) // TODO this field will be replaced by a proper registry later
-	private static @UnknownNullability ExperimentRegistry experimentRegistry;
 
 	public static Version getVersion() {
 		final Version v = version;
@@ -339,9 +337,13 @@ public static void disableHookRegistration(Class<? extends Hook<?>>... hooks) {
 
 	/**
 	 * @return The manager for experimental, optional features.
+	 * @deprecated {@link ExperimentRegistry} is now a regular registry, and should be accessed as such.
+	 * See {@link org.skriptlang.skript.addon.SkriptAddon#registry(Class)}.
 	 */
+	@Deprecated(since = "INSERT VERSION", forRemoval = true)
 	public static ExperimentRegistry experiments() {
-		return experimentRegistry;
+		// intentionally returning the modifiable view
+		return skript.registry(ExperimentRegistry.class);
 	}
 
 	/**
@@ -469,8 +471,8 @@ public void onEnable() {
 		// initialize the old Skript SkriptAddon instance
 		getAddonInstance();
 
-		experimentRegistry = new ExperimentRegistry(this);
-		Feature.registerAll(getAddonInstance(), experimentRegistry);
+		skript.storeRegistry(ExperimentRegistry.class, new ExperimentRegistry(skript));
+		Feature.registerAll(skript, skript.registry(ExperimentRegistry.class));
 
 		skript.storeRegistry(PropertyRegistry.class, new PropertyRegistry(this));
 		Property.registerDefaultProperties();
@@ -1286,8 +1288,6 @@ public void onDisable() {
 				Skript.exception(e, "An error occurred while shutting down.", "This might or might not cause any issues.");
 			}
 		}
-
-		this.experimentRegistry = null;
 	}
 
 	// ================ CONSTANTS, OPTIONS & OTHER ================

src/main/java/ch/njol/skript/registrations/Feature.java

@@ -1,17 +1,17 @@
 package ch.njol.skript.registrations;
 
-import ch.njol.skript.SkriptAddon;
 import ch.njol.skript.doc.Documentable;
 import ch.njol.skript.patterns.PatternCompiler;
 import ch.njol.skript.patterns.SkriptPattern;
 import com.google.common.base.Preconditions;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Unmodifiable;
+import org.skriptlang.skript.addon.SkriptAddon;
 import org.skriptlang.skript.lang.experiment.Experiment;
 import org.skriptlang.skript.lang.experiment.ExperimentRegistry;
 import org.skriptlang.skript.lang.experiment.LifeCycle;
 
-import java.util.Collection;
 import java.util.List;
 
 /**
@@ -209,6 +209,7 @@ set the damage location to location(0, 0, 10)
 		};
 	}
 
+	@ApiStatus.Internal
 	public static void registerAll(SkriptAddon addon, ExperimentRegistry manager) {
 		for (Feature value : values()) {
 			manager.register(addon, value);

src/main/java/org/skriptlang/skript/lang/experiment/ExperimentRegistry.java

@@ -1,32 +1,55 @@
 package org.skriptlang.skript.lang.experiment;
 
-import ch.njol.skript.Skript;
-import ch.njol.skript.SkriptAddon;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Unmodifiable;
+import org.skriptlang.skript.Skript;
+import org.skriptlang.skript.addon.SkriptAddon;
 import org.skriptlang.skript.lang.script.Script;
+import org.skriptlang.skript.util.Registry;
+import org.skriptlang.skript.util.ViewProvider;
 
 import java.util.LinkedHashSet;
 import java.util.Set;
 
 /**
  * A manager for registering (and identifying) experimental feature flags.
  */
-/*
-* TODO
-* 	This is designed to be (replaced by|refactored into) a proper registry when the registries rework PR
-* 	is completed. The overall skeleton is designed to remain, so that there should be no breaking changes
-* 	for anything using it. I.e. you will still be able to use Skript#experiments() and obtain 'this' class
-* 	although these will just become helper methods for the proper registry behaviour.
-* */
-public class ExperimentRegistry implements Experimented {
+public class ExperimentRegistry implements Registry<Experiment>, ViewProvider<ExperimentRegistry>, Experimented {
 
 	private final Skript skript;
 	private final Set<Experiment> experiments;
+	private final @Nullable ExperimentRegistry source;
 
 	public ExperimentRegistry(Skript skript) {
 		this.skript = skript;
 		this.experiments = new LinkedHashSet<>();
+		this.source = null;
+	}
+
+	/**
+	 * Internal constructor for creating an unmodifiable view of an experiment registry.
+	 */
+	private ExperimentRegistry(ExperimentRegistry source) {
+		this.skript = source.skript;
+		this.experiments = source.experiments;
+		this.source = source;
+	}
+
+	/**
+	 * @deprecated Use {@link #ExperimentRegistry(Skript)}.
+	 */
+	@Deprecated(since = "INSERT VERSION", forRemoval = true)
+	public ExperimentRegistry(ch.njol.skript.Skript ignored) {
+		this(ch.njol.skript.Skript.instance());
+	}
+
+	/**
+	 * @return An unmodifiable view of this experiment registry.
+	 */
+	@Override
+	public ExperimentRegistry unmodifiableView() {
+		return new ExperimentRegistry(this);
 	}
 
 	/**
@@ -52,6 +75,14 @@ public Experiment[] registered() {
 		return experiments.toArray(new Experiment[0]);
 	}
 
+	/**
+	 * @return An unmodifiable set containing all currently-registered experiments.
+	 */
+	@Override
+	public @Unmodifiable Set<Experiment> elements() {
+		return Set.copyOf(experiments);
+	}
+
 	/**
 	 * Registers a new experimental feature flag, which will be available to scripts
 	 * with the {@code using %name%} structure.
@@ -60,6 +91,9 @@ public Experiment[] registered() {
 	 * @param experiment The experimental feature flag.
 	 */
 	public void register(SkriptAddon addon, Experiment experiment) {
+		if (source != null) {
+			throw new UnsupportedOperationException("Cannot register experiments using an unmodifiable registry.");
+		}
 		// the addon instance is requested for now in case we need it in future (for error triage)
 		this.experiments.add(experiment);
 	}
@@ -81,6 +115,9 @@ public void registerAll(SkriptAddon addon, Experiment... experiments) {
 	 * @param experiment The experimental feature flag.
 	 */
 	public void unregister(SkriptAddon addon, Experiment experiment) {
+		if (source != null) {
+			throw new UnsupportedOperationException("Cannot unregister experiments using an unmodifiable registry.");
+		}
 		// the addon instance is requested for now in case we need it in future (for error triage)
 		this.experiments.remove(experiment);
 	}