PaperMC/Remapped-Spigot-Server-Patches/0526-Fix-Concurrency-issue-in-WeightedList.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 6 Jul 2020 18:36:41 -0400
Subject: [PATCH] Fix Concurrency issue in WeightedList

if multiple threads from worldgen sort at same time, it will crash.
So make a copy of the list for sorting purposes.

diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java b/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
index 0a65e442ddc31c06f3bb0ff5aa152daee7a210af..a81ad258b39b7472312ab1bedeeacaf26ffae4f7 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
@@ -17,7 +17,7 @@ public class GateBehavior<E extends LivingEntity> extends Behavior<E> {
     private final Set<MemoryModuleType<?>> exitErasedMemories;
     private final GateBehavior.OrderPolicy orderPolicy;
     private final GateBehavior.RunningPolicy runningPolicy;
-    private final WeightedList<Behavior<? super E>> behaviors = new WeightedList<>();
+    private final WeightedList<Behavior<? super E>> behaviors = new WeightedList<>(false); // Paper - don't use a clone
 
     public GateBehavior(Map<MemoryModuleType<?>, MemoryStatus> requiredMemoryState, Set<MemoryModuleType<?>> memoriesToForgetWhenStopped, GateBehavior.OrderPolicy order, GateBehavior.RunningPolicy runMode, List<Pair<Behavior<? super E>, Integer>> tasks) {
         super(requiredMemoryState);
@@ -65,10 +65,9 @@ public class GateBehavior<E extends LivingEntity> extends Behavior<E> {
         }).forEach((behavior) -> {
             behavior.g(world, entity, time);
         });
-        Set set = this.exitErasedMemories;
         Brain behaviorcontroller = entity.getBrain();
 
-        set.forEach(behaviorcontroller::removeMemory);
+        this.exitErasedMemories.forEach(behaviorcontroller::eraseMemory); // Paper - decomp fix
     }
 
     @Override
@@ -111,11 +110,11 @@ public class GateBehavior<E extends LivingEntity> extends Behavior<E> {
     static enum OrderPolicy {
 
         ORDERED((weightedlist) -> {
-        }), SHUFFLED(WeightedList::a);
+        }), SHUFFLED(WeightedList::shuffle);
 
         private final Consumer<WeightedList<?>> consumer;
 
-        private OrderPolicy(Consumer consumer) {
+        private OrderPolicy(Consumer<WeightedList<?>> consumer) { // Paper - decomp fix
             this.consumer = consumer;
         }
 
diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/WeightedList.java b/src/main/java/net/minecraft/world/entity/ai/behavior/WeightedList.java
index e4c1c58e9a9c744c7ebb9948a27766b84a081b9e..85df30ef7c03c2f8ae741a8cac8bf601490d2539 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/WeightedList.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/WeightedList.java
@@ -6,7 +6,7 @@ import com.mojang.serialization.Codec;
 import com.mojang.serialization.DataResult;
 import com.mojang.serialization.Dynamic;
 import com.mojang.serialization.DynamicOps;
-import com.mojang.serialization.OptionalDynamic;
+
 import java.util.Comparator;
 import java.util.List;
 import java.util.Random;
@@ -14,26 +14,32 @@ import java.util.stream.Stream;
 
 public class WeightedList<U> {
 
-    protected final List<WeightedList.WeightedEntry<U>> entries;
+    protected final List<WeightedList.WeightedEntry<U>> list; // Paper - decompile conflict
     private final Random random;
+    private final boolean isUnsafe; // Paper
 
-    public WeightedList() {
-        this(Lists.newArrayList());
+    // Paper start - add useClone option
+    public WeightedList() { this(true); }
+    public WeightedList(boolean isUnsafe) {
+        this(Lists.newArrayList(), isUnsafe);
     }
 
-    private WeightedList(List<WeightedList.WeightedEntry<U>> entries) {
+    private WeightedList(List<WeightedList.WeightedEntry<U>> entries) { this(entries, true); }
+    private WeightedList(List<WeightedList.WeightedEntry<U>> list, boolean isUnsafe) {
+        this.isUnsafe = isUnsafe;
+        // Paper end
         this.random = new Random();
-        this.entries = Lists.newArrayList(entries);
+        this.list = Lists.newArrayList(list); // Paper - decompile conflict
     }
 
     public static <U> Codec<WeightedList<U>> codec(Codec<U> codec) {
-        return WeightedList.entries.a(codec).listOf().xmap(WeightedList::new, (weightedlist) -> {
-            return weightedlist.a;
+        return WeightedList.WeightedEntry.codec(codec).listOf().xmap(WeightedList::new, (weightedlist) -> { // Paper - decompile conflict
+            return weightedlist.list; // Paper - decompile conflict
         });
     }
 
     public WeightedList<U> add(U item, int weight) {
-        this.entries.add(new WeightedList.WeightedEntry<>(item, weight));
+        this.list.add(new WeightedList.WeightedEntry<>(item, weight)); // Paper - decompile conflict
         return this;
     }
 
@@ -42,21 +48,20 @@ public class WeightedList<U> {
     }
 
     public WeightedList<U> shuffle(Random random) {
-        this.entries.forEach((weightedlist_a) -> {
-            weightedlist_a.setRandom(random.nextFloat());
-        });
-        this.entries.sort(Comparator.comparingDouble((object) -> {
-            return ((WeightedList.WeightedEntry) object).getRandWeight();
-        }));
-        return this;
+        // Paper start - make concurrent safe, work off a clone of the list
+        List<WeightedList.WeightedEntry<U>> list = isUnsafe ? new java.util.ArrayList<WeightedList.WeightedEntry<U>>(this.list) : this.list;
+        list.forEach((weightedlist_a) -> weightedlist_a.setRandom(random.nextFloat()));
+        list.sort(Comparator.comparingDouble(WeightedEntry::getRandWeight));
+        return isUnsafe ? new WeightedList<>(list, isUnsafe) : this;
+        // Paper end
     }
 
     public boolean isEmpty() {
-        return this.entries.isEmpty();
+        return this.list.isEmpty(); // Paper - decompile conflict
     }
 
     public Stream<U> stream() {
-        return this.entries.stream().map(WeightedList.entries::a);
+        return this.list.stream().map(WeightedList.WeightedEntry::getData); // Paper - decompile conflict
     }
 
     public U getOne(Random random) {
@@ -64,7 +69,7 @@ public class WeightedList<U> {
     }
 
     public String toString() {
-        return "WeightedList[" + this.entries + "]";
+        return "WeightedList[" + this.list + "]"; // Paper - decompile conflict
     }
 
     public static class WeightedEntry<T> {
@@ -98,11 +103,7 @@ public class WeightedList<U> {
             return new Codec<WeightedList.WeightedEntry<E>>() {
                 public <T> DataResult<Pair<WeightedList.WeightedEntry<E>, T>> decode(DynamicOps<T> dynamicops, T t0) {
                     Dynamic<T> dynamic = new Dynamic(dynamicops, t0);
-                    OptionalDynamic optionaldynamic = dynamic.get("data");
-                    Codec codec1 = codec;
-
-                    codec.getClass();
-                    return optionaldynamic.flatMap(codec1::parse).map((object) -> {
+                    return dynamic.get("data").flatMap(codec::parse).map((object) -> { // Paper - decompile error
                         return new WeightedList.WeightedEntry<>(object, dynamic.get("weight").asInt(1));
                     }).map((weightedlist_a) -> {
                         return Pair.of(weightedlist_a, dynamicops.empty());