Merge branch 'master' into master

src/main/java/me/clip/placeholderapi/PlaceholderAPI.java

@@ -345,12 +345,13 @@ public class PlaceholderAPI {
   }
 
   public static boolean registerExpansion(PlaceholderExpansion ex) {
-    if (registerPlaceholderHook(ex.getIdentifier(), ex)) {
-      Bukkit.getPluginManager().callEvent(new ExpansionRegisterEvent(ex));
-      return true;
+    ExpansionRegisterEvent ev = new ExpansionRegisterEvent(ex);
+    Bukkit.getPluginManager().callEvent(ev);
+    if (ev.isCancelled()) {
+      return false;
     }
-
-    return false;
+    
+    return registerPlaceholderHook(ex.getIdentifier(), ex);
   }
 
   public static boolean unregisterExpansion(PlaceholderExpansion ex) {

src/main/java/me/clip/placeholderapi/events/ExpansionRegisterEvent.java

@@ -21,13 +21,16 @@
 package me.clip.placeholderapi.events;
 
 import me.clip.placeholderapi.expansion.PlaceholderExpansion;
+import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
 
-public class ExpansionRegisterEvent extends Event {
+public class ExpansionRegisterEvent extends Event implements Cancellable {
 
   private static final HandlerList HANDLERS = new HandlerList();
   private final PlaceholderExpansion expansion;
+  private boolean isCancelled;
+
 
   public ExpansionRegisterEvent(PlaceholderExpansion expansion) {
     this.expansion = expansion;
@@ -45,4 +48,14 @@ public class ExpansionRegisterEvent extends Event {
   public PlaceholderExpansion getExpansion() {
     return expansion;
   }
+
+  @Override
+  public boolean isCancelled() {
+    return isCancelled;
+  }
+
+  @Override
+  public void setCancelled(boolean b) {
+    this.isCancelled = b;
+  }
 }

src/main/java/me/clip/placeholderapi/expansion/PlaceholderExpansion.java

@@ -98,7 +98,7 @@ public abstract class PlaceholderExpansion extends PlaceholderHook {
    */
   public boolean isRegistered() {
     Validate.notNull(getIdentifier(), "Placeholder identifier can not be null!");
-    return PlaceholderAPI.getRegisteredIdentifiers().contains(getIdentifier());
+    return PlaceholderAPI.isRegistered(getIdentifier());
   }
 
   /**