Supported events

src/main/java/ch/njol/skript/expressions/ExprExplodedBlocks.java

@@ -48,16 +48,17 @@ public class ExprExplodedBlocks extends SimpleExpression<Block> {
 	static {
 		Skript.registerExpression(ExprExplodedBlocks.class, Block.class, ExpressionType.COMBINED, "[the] exploded blocks");
 	}
-	
+
 	@Override
 	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, SkriptParser.ParseResult parseResult) {
-		if (!getParser().isCurrentEvent(EntityExplodeEvent.class)) {
-			Skript.error("Exploded blocks can only be retrieved from an explode event.");
-			return false;
-		}
 		return true;
 	}
-
+
+	@Override
+	public Class<? extends Event>[] supportedEvents() {
+		return CollectionUtils.array(EntityExplodeEvent.class);
+	}
+
 	@Nullable
 	@Override
 	protected Block[] get(Event e) {

src/main/java/ch/njol/skript/lang/SkriptParser.java

@@ -31,19 +31,14 @@
 import ch.njol.util.StringUtils;
 import ch.njol.util.coll.CollectionUtils;
 import com.google.common.primitives.Booleans;
+import org.bukkit.event.Event;
 import org.bukkit.plugin.java.JavaPlugin;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.skriptlang.skript.lang.script.Script;
 import org.skriptlang.skript.lang.script.ScriptWarning;
 
-import java.util.ArrayList;
-import java.util.Deque;
-import java.util.Iterator;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
+import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
@@ -225,7 +220,21 @@ public boolean hasTag(String tag) {
 								}
 							}
 							T element = info.getElementClass().newInstance();
-							if (element.init(parseResult.exprs, patternIndex, getParser().getHasDelayBefore(), parseResult)) {
+
+							Class<? extends Event>[] supportedEvents = element.supportedEvents();
+							if (supportedEvents.length > 0 && !getParser().isCurrentEvent(supportedEvents)) {
+								StringJoiner joiner = new StringJoiner(", ", "the ", "");
+
+								Arrays.stream(supportedEvents)
+									.map(it -> it.getSimpleName().replaceAll("([A-Z])", " $1").toLowerCase().trim())
+									.forEachOrdered(joiner::add);
+
+								Skript.error("'" + parseResult.expr + "' can only be used in " + joiner);
+                                continue;
+                            }
+
+							boolean success = element.init(parseResult.exprs, patternIndex, getParser().getHasDelayBefore(), parseResult);
+							if (success) {
 								log.printLog();
 								return element;
 							}

src/main/java/ch/njol/skript/lang/SyntaxElement.java

@@ -3,6 +3,7 @@
 import ch.njol.skript.lang.SkriptParser.ParseResult;
 import ch.njol.skript.lang.parser.ParserInstance;
 import ch.njol.util.Kleenean;
+import org.bukkit.event.Event;
 
 /**
  * Represents a general part of the syntax.
@@ -29,4 +30,20 @@ default ParserInstance getParser() {
 		return ParserInstance.get();
 	}
 
+	/**
+	 * Returns all supported events for this syntax element. By default, all events are accepted.
+	 * <p>
+	 * Before {@link #init(Expression[], int, Kleenean, ParseResult)} is called, checks
+	 * to see if the current event is supported by this syntax element.
+	 * If it is not, an error will be printed and the syntax element will not be initialised.
+	 * </p>
+	 *
+	 * @return All supported event classes.
+	 * @see ch.njol.util.coll.CollectionUtils#array(Object[])
+	 */
+	default Class<? extends Event>[] supportedEvents() {
+		//noinspection unchecked
+		return (Class<? extends Event>[]) new Class[0];
+	}
+
 }

src/test/skript/tests/misc/supported events.sk

@@ -0,0 +1,5 @@
+test "supported events":
+	parse:
+		set {_x} to the exploded blocks
+
+	assert last parse logs contain "'the exploded blocks' can only be used in the entity explode event" with "supported events message did not get sent correctly"