Filter cancelled events even when the declared class is not cancellable (#3798)

* Filter cancelled events even when the declared class is not cancellable

* Remove InvalidCancelledListener test

src/main/java/org/spongepowered/common/event/filter/FilterGenerator.java

@@ -47,7 +47,6 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Type;
-import org.spongepowered.api.event.Cancellable;
 import org.spongepowered.api.event.Event;
 import org.spongepowered.api.event.filter.Getter;
 import org.spongepowered.api.event.filter.IsCancelled;
@@ -144,7 +143,7 @@ public class FilterGenerator {
                 }
             }
         }
-        if (!cancellation && Cancellable.class.isAssignableFrom(parameters[0].clazz())) {
+        if (!cancellation) {
             additional.add(new CancellationEventFilterDelegate(Tristate.FALSE));
         }
 

src/main/java/org/spongepowered/common/event/filter/delegate/CancellationEventFilterDelegate.java

@@ -30,6 +30,7 @@ import static org.objectweb.asm.Opcodes.ARETURN;
 import static org.objectweb.asm.Opcodes.CHECKCAST;
 import static org.objectweb.asm.Opcodes.IFEQ;
 import static org.objectweb.asm.Opcodes.IFNE;
+import static org.objectweb.asm.Opcodes.INSTANCEOF;
 import static org.objectweb.asm.Opcodes.INVOKEINTERFACE;
 
 import org.objectweb.asm.ClassWriter;
@@ -60,21 +61,43 @@ public class CancellationEventFilterDelegate implements FilterDelegate {
         if (this.state == Tristate.UNDEFINED) {
             return locals;
         }
-        if (!Cancellable.class.isAssignableFrom(method.parameterTypes()[0].clazz())) {
-            throw new IllegalStateException("Attempted to filter a non-cancellable event type by its cancellation status");
+
+        final boolean checkCancellable = !Cancellable.class.isAssignableFrom(method.parameterTypes()[0].clazz());
+        final String cancellableClassName = Type.getInternalName(Cancellable.class);
+        final Label notCancelled = new Label();
+
+        if (checkCancellable) {
+            mv.visitVarInsn(ALOAD, 1);
+            mv.visitTypeInsn(INSTANCEOF, cancellableClassName);
+            mv.visitJumpInsn(IFEQ, notCancelled);
         }
+
         mv.visitVarInsn(ALOAD, 1);
-        mv.visitTypeInsn(CHECKCAST, Type.getInternalName(Cancellable.class));
-        mv.visitMethodInsn(INVOKEINTERFACE, Type.getInternalName(Cancellable.class), "isCancelled", "()Z", true);
-        final Label success = new Label();
-        if (this.state == Tristate.TRUE) {
-            mv.visitJumpInsn(IFNE, success);
-        } else {
-            mv.visitJumpInsn(IFEQ, success);
+        if (checkCancellable) {
+            mv.visitTypeInsn(CHECKCAST, cancellableClassName);
         }
-        mv.visitInsn(ACONST_NULL);
-        mv.visitInsn(ARETURN);
-        mv.visitLabel(success);
+        mv.visitMethodInsn(INVOKEINTERFACE, cancellableClassName, "isCancelled", "()Z", true);
+
+        if (this.state == Tristate.TRUE) {
+            final Label cancelled = new Label();
+            mv.visitJumpInsn(IFNE, cancelled);
+
+            if (checkCancellable) {
+                mv.visitLabel(notCancelled);
+            }
+            mv.visitInsn(ACONST_NULL);
+            mv.visitInsn(ARETURN);
+
+            mv.visitLabel(cancelled);
+        } else {
+            mv.visitJumpInsn(IFEQ, notCancelled);
+
+            mv.visitInsn(ACONST_NULL);
+            mv.visitInsn(ARETURN);
+
+            mv.visitLabel(notCancelled);
+        }
+
         return locals;
     }
 

src/test/invalid/common/event/EventFilterTest.java

@@ -53,7 +53,6 @@ import org.spongepowered.common.event.listener.DoubleListener;
 import org.spongepowered.common.event.listener.FirstLastCauseListener;
 import org.spongepowered.common.event.listener.GetterListener;
 import org.spongepowered.common.event.listener.IncludeExcludeListener;
-import org.spongepowered.common.event.listener.InvalidCancelledListener;
 import org.spongepowered.common.event.listener.InvalidIncludeExcludeListener;
 import org.spongepowered.common.event.listener.RootListener;
 import org.spongepowered.common.event.listener.SimpleListener;
@@ -117,11 +116,6 @@ public class EventFilterTest {
         Assert.assertTrue("Listener annotated with @IsCancelled(Tristate.UNDEFINED) was not called!", listener.alwaysCalledWasCalled);
     }
 
-    @Test(expected = RuntimeException.class)
-    public void testCancelledEvent_InvalidListener() throws Exception {
-        this.getListener(new InvalidCancelledListener(), "onEvent", UncancellableEvent.class);
-    }
-
     @Test
     public void testIncludeExcludeListener() throws Exception {
         IncludeExcludeListener listener = new IncludeExcludeListener();
@@ -461,14 +455,6 @@ public class EventFilterTest {
         }
     }
 
-    public static class UncancellableEvent implements Event {
-
-        @Override
-        public Cause getCause() {
-            return TEST_CAUSE;
-        }
-    }
-
     public static class TestObject {
 
     }

src/test/invalid/common/event/listener/InvalidCancelledListener.java

@@ -1,38 +0,0 @@
-/*
- * This file is part of Sponge, licensed under the MIT License (MIT).
- *
- * Copyright (c) SpongePowered <https://www.spongepowered.org>
- * Copyright (c) contributors
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-package org.spongepowered.common.event.listener;
-
-import org.spongepowered.api.event.Listener;
-import org.spongepowered.api.event.filter.IsCancelled;
-import org.spongepowered.common.event.EventFilterTest;
-
-public class InvalidCancelledListener {
-
-    @Listener
-    @IsCancelled
-    public void onEvent(EventFilterTest.UncancellableEvent event) {
-    }
-
-}