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Add "cancel on error" option for event listeners #11691

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Add "cancel on error" option for event listeners #11691

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183 changes: 183 additions & 0 deletions patches/api/0501-Add-cancel-on-error-option-for-events.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,183 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Newwind <newwindserver@gmail.com>
Date: Sat, 30 Nov 2024 16:03:37 +0200
Subject: [PATCH] Add cancel on error option for event listeners

Add the option to cancel an event if an error is thrown inside its handler
useful for mission critical listeners, for example, preventing players from breaking blocks in an area
or preventing players from modifying certain items inside an anvil

diff --git a/src/main/java/org/bukkit/event/EventHandler.java b/src/main/java/org/bukkit/event/EventHandler.java
index cc06f480..dd0ac8a5 100644
--- a/src/main/java/org/bukkit/event/EventHandler.java
+++ b/src/main/java/org/bukkit/event/EventHandler.java
@@ -38,4 +38,16 @@ public @interface EventHandler {
* @return whether cancelled events should be ignored
*/
boolean ignoreCancelled() default false;
+
+ // Paper start - Add cancel on error
+ /**
+ * Define if the event should be cancelled when an error is thrown inside the handler.
+ * <p>
+ * If cancelOnError is true and the event runs into an error, it will be cancelled.
+ * Can still be uncancelled if an event with higher priority runs setCancelled(false)
+ *
+ * @return whether thrown errors should cancel the event
+ */
+ boolean cancelOnError() default false;
+ // Paper end
}
diff --git a/src/main/java/org/bukkit/plugin/PluginManager.java b/src/main/java/org/bukkit/plugin/PluginManager.java
index 47153dee..fdbff1f7 100644
--- a/src/main/java/org/bukkit/plugin/PluginManager.java
+++ b/src/main/java/org/bukkit/plugin/PluginManager.java
@@ -152,6 +152,21 @@ public interface PluginManager extends io.papermc.paper.plugin.PermissionManager
*/
public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled);

+ // Paper start - Add cancel on error
+ /**
+ * Registers the specified executor to the given event class
+ *
+ * @param event Event type to register
+ * @param listener Listener to register
+ * @param priority Priority to register this event at
+ * @param executor EventExecutor to register
+ * @param plugin Plugin to register
+ * @param ignoreCancelled Whether to pass cancelled events or not
+ * @param cancelOnError Whether the event should be cancelled when an error is thrown inside the handler.
+ */
+ public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled, boolean cancelOnError);
+ // Paper end
+
/**
* Enables the specified plugin
* <p>
diff --git a/src/main/java/org/bukkit/plugin/RegisteredListener.java b/src/main/java/org/bukkit/plugin/RegisteredListener.java
index 3b3d9642..39155687 100644
--- a/src/main/java/org/bukkit/plugin/RegisteredListener.java
+++ b/src/main/java/org/bukkit/plugin/RegisteredListener.java
@@ -16,6 +16,7 @@ public class RegisteredListener {
private final Plugin plugin;
private final EventExecutor executor;
private final boolean ignoreCancelled;
+ private final boolean cancelOnError; // Paper - Add cancel on error

public RegisteredListener(@NotNull final Listener listener, @NotNull final EventExecutor executor, @NotNull final EventPriority priority, @NotNull final Plugin plugin, final boolean ignoreCancelled) {
this.listener = listener;
@@ -23,8 +24,20 @@ public class RegisteredListener {
this.plugin = plugin;
this.executor = executor;
this.ignoreCancelled = ignoreCancelled;
+ this.cancelOnError = false; // Paper - Add cancel on error
}

+ // Paper start - Add cancel on error
+ public RegisteredListener(@NotNull final Listener listener, @NotNull final EventExecutor executor, @NotNull final EventPriority priority, @NotNull final Plugin plugin, final boolean ignoreCancelled, final boolean cancelOnError) {
+ this.listener = listener;
+ this.priority = priority;
+ this.plugin = plugin;
+ this.executor = executor;
+ this.ignoreCancelled = ignoreCancelled;
+ this.cancelOnError = cancelOnError;
+ }
+ // Paper end
+
/**
* Gets the listener for this registration
*
@@ -79,6 +92,17 @@ public class RegisteredListener {
return ignoreCancelled;
}

+ // Paper start - Add cancel on error
+ /**
+ * Whether this listener cancels events on error
+ *
+ * @return whether thrown errors should cancel the event
+ */
+ public boolean willCancelOnError() {
+ return cancelOnError;
+ }
+ // Paper end
+
// Paper start
/**
* Get the executor for this registration.
@@ -98,6 +122,7 @@ public class RegisteredListener {
+ "\", executor=\"" + this.executor
+ "\", priority=\"" + this.priority.name() + " (" + this.priority.getSlot() + ")"
+ "\", ignoringCancelled=" + this.ignoreCancelled
+ + "\", cancelOnError=" + this.cancelOnError
+ "}";
}
// Paper end
diff --git a/src/main/java/org/bukkit/plugin/SimplePluginManager.java b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
index b878e716..42b434ff 100644
--- a/src/main/java/org/bukkit/plugin/SimplePluginManager.java
+++ b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
@@ -667,6 +667,12 @@ public final class SimplePluginManager implements PluginManager {
));
}
} catch (Throwable ex) {
+ // Paper start - Add cancel on error
+ if (registration.willCancelOnError() && event instanceof org.bukkit.event.Cancellable cancellable) {
+ cancellable.setCancelled(true);
+ }
+ // Paper end
+
// Paper start - error reporting
String msg = "Could not pass event " + event.getEventName() + " to " + registration.getPlugin().getDescription().getFullName();
server.getLogger().log(Level.SEVERE, msg, ex);
@@ -696,6 +702,13 @@ public final class SimplePluginManager implements PluginManager {
registerEvent(event, listener, priority, executor, plugin, false);
}

+ // Paper start - Add cancel on error
+ @Override
+ public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled) {
+ registerEvent(event, listener, priority, executor, plugin, false, false);
+ }
+ // Paper end
+
/**
* Registers the given event to the specified listener using a directly
* passed EventExecutor
@@ -705,11 +718,11 @@ public final class SimplePluginManager implements PluginManager {
* @param priority Priority of this event
* @param executor EventExecutor to register
* @param plugin Plugin to register
- * @param ignoreCancelled Do not call executor if event was already
- * cancelled
+ * @param ignoreCancelled Do not call executor if event was already cancelled
+ * @param cancelOnError Whether the event should be cancelled when an error is thrown inside the handler.
*/
@Override
- public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled) {
+ public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled, boolean cancelOnError) { // Paper - Add cancel on error
Preconditions.checkArgument(listener != null, "Listener cannot be null");
Preconditions.checkArgument(priority != null, "Priority cannot be null");
Preconditions.checkArgument(executor != null, "Executor cannot be null");
@@ -724,7 +737,7 @@ public final class SimplePluginManager implements PluginManager {
if (false) { // Spigot - RL handles useTimings check now // Paper
getEventListeners(event).register(new TimedRegisteredListener(listener, executor, priority, plugin, ignoreCancelled));
} else {
- getEventListeners(event).register(new RegisteredListener(listener, executor, priority, plugin, ignoreCancelled));
+ getEventListeners(event).register(new RegisteredListener(listener, executor, priority, plugin, ignoreCancelled, cancelOnError)); // Paper - Add cancel on error
}
}

diff --git a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
index eaefbb00..b1431102 100644
--- a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
+++ b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
@@ -311,7 +311,7 @@ public final class JavaPluginLoader implements PluginLoader {
if (false) { // Spigot - RL handles useTimings check now
eventSet.add(new TimedRegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled()));
} else {
- eventSet.add(new RegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled()));
+ eventSet.add(new RegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled(), eh.cancelOnError())); // Paper - Add cancel on error
}
}
return ret;
84 changes: 84 additions & 0 deletions patches/server/1073-Add-cancel-on-error-option-for-events.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,84 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Newwind <newwindserver@gmail.com>
Date: Sat, 30 Nov 2024 16:03:37 +0200
Subject: [PATCH] Add cancel on error option for event listeners

Add the option to cancel an event if an error is thrown inside its handler
useful for mission critical listeners, for example, preventing players from breaking blocks in an area
or preventing players from modifying certain items inside an anvil

diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
index 419065d6c..8637fc75c 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
@@ -66,6 +66,12 @@ class PaperEventManager {
));
}
} catch (Throwable ex) {
+ // Paper start - Add cancel on error
+ if (registration.willCancelOnError() && event instanceof org.bukkit.event.Cancellable cancellable) {
+ cancellable.setCancelled(true);
+ }
+ // Paper end
+
String msg = "Could not pass event " + event.getEventName() + " to " + registration.getPlugin().getPluginMeta().getDisplayName();
this.server.getLogger().log(Level.SEVERE, msg, ex);
if (!(event instanceof ServerExceptionEvent)) { // We don't want to cause an endless event loop

diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
index 7ce9ebba8..419065d6c 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
@@ -90,13 +90,19 @@ class PaperEventManager {
this.registerEvent(event, listener, priority, executor, plugin, false);
}

+ // Paper start - Add cancel on error
public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled) {
+ this.registerEvent(event, listener, priority, executor, plugin, false, false);
+ }
+ // Paper end
+
+ public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled, boolean cancelOnError) { // Paper - Add cancel on error
if (!plugin.isEnabled()) {
throw new IllegalPluginAccessException("Plugin attempted to register " + event + " while not enabled");
}

executor = new TimedEventExecutor(executor, plugin, null, event);
- this.getEventListeners(event).register(new RegisteredListener(listener, executor, priority, plugin, ignoreCancelled));
+ this.getEventListeners(event).register(new RegisteredListener(listener, executor, priority, plugin, ignoreCancelled, cancelOnError));
}

@NotNull
diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginManagerImpl.java b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginManagerImpl.java
index 097500a59..34349b5fa 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginManagerImpl.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginManagerImpl.java
@@ -146,6 +146,13 @@ public class PaperPluginManagerImpl implements PluginManager, DependencyContext
this.paperEventManager.registerEvent(event, listener, priority, executor, plugin, ignoreCancelled);
}

+ // Paper start - Add cancel on error
+ @Override
+ public void registerEvent(@NotNull Class<? extends Event> event, @NotNull Listener listener, @NotNull EventPriority priority, @NotNull EventExecutor executor, @NotNull Plugin plugin, boolean ignoreCancelled, boolean cancelOnError) {
+ this.paperEventManager.registerEvent(event, listener, priority, executor, plugin, ignoreCancelled, cancelOnError);
+ }
+ // Paper end
+
// Permission manipulation

@Override

diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
index 8637fc75c..4df0ca82b 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperEventManager.java
@@ -195,7 +195,7 @@ class PaperEventManager {
}

EventExecutor executor = new TimedEventExecutor(EventExecutor.create(method, eventClass), plugin, method, eventClass);
- eventSet.add(new RegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled()));
+ eventSet.add(new RegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled(), eh.cancelOnError()));
}
return ret;
}
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