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Fix async command building throwing CME in some cases #13233

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Fix async command building throwing CME in some cases #13233

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8 changes: 6 additions & 2 deletions paper-server/patches/sources/com/mojang/brigadier/tree/CommandNode.java.patch
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Original file line number Diff line number Diff line change
@@ -1,7 +1,11 @@
--- a/com/mojang/brigadier/tree/CommandNode.java
+++ b/com/mojang/brigadier/tree/CommandNode.java
@@ -27,11 +_,22 @@
private final Map<String, CommandNode<S>> children = new LinkedHashMap<>();
@@ -24,14 +_,25 @@
import java.util.function.Predicate;

public abstract class CommandNode<S> implements Comparable<CommandNode<S>> {
- private final Map<String, CommandNode<S>> children = new LinkedHashMap<>();
+ public final Map<String, CommandNode<S>> children = Collections.synchronizedMap(new LinkedHashMap<>()); // Paper - Prevent concurrent modification when sending commands; public
private final Map<String, LiteralCommandNode<S>> literals = new LinkedHashMap<>();
private final Map<String, ArgumentCommandNode<S, ?>> arguments = new LinkedHashMap<>();
- private final Predicate<S> requirement;
Expand Down
28 changes: 12 additions & 16 deletions paper-server/patches/sources/net/minecraft/commands/Commands.java.patch
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Original file line number Diff line number Diff line change
Expand Up @@ -132,7 +132,7 @@
}

return null;
@@ -399,17 +_,110 @@
@@ -399,17 +_,109 @@
}

public void sendCommands(ServerPlayer player) {
Expand All @@ -145,9 +145,7 @@
+ // CraftBukkit start
+ // Register Vanilla commands into builtRoot as before
+ // Paper start - Perf: Async command map building
+ // Copy root children to avoid concurrent modification during building
+ final java.util.Collection<CommandNode<CommandSourceStack>> commandNodes = new java.util.ArrayList<>(this.dispatcher.getRoot().getChildren());
+ COMMAND_SENDING_POOL.execute(() -> this.sendAsync(player, commandNodes));
+ COMMAND_SENDING_POOL.execute(() -> this.sendAsync(player));
+ }
+
+ // Fixed pool, but with discard policy
Expand All @@ -161,13 +159,12 @@
+ new java.util.concurrent.ThreadPoolExecutor.DiscardPolicy()
+ );
+
+ private void sendAsync(ServerPlayer player, java.util.Collection<CommandNode<CommandSourceStack>> dispatcherRootChildren) {
+ private void sendAsync(ServerPlayer player) {
+ // Paper end - Perf: Async command map building
Map<CommandNode<CommandSourceStack>, CommandNode<CommandSourceStack>> map = new HashMap<>();
RootCommandNode<CommandSourceStack> rootCommandNode = new RootCommandNode<>();
map.put(this.dispatcher.getRoot(), rootCommandNode);
- fillUsableCommands(this.dispatcher.getRoot(), rootCommandNode, player.createCommandSourceStack(), map);
+ fillUsableCommands(dispatcherRootChildren, rootCommandNode, player.createCommandSourceStack(), map); // Paper - Perf: Async command map building; pass copy of children
fillUsableCommands(this.dispatcher.getRoot(), rootCommandNode, player.createCommandSourceStack(), map);
+
+ java.util.Collection<String> bukkit = new java.util.LinkedHashSet<>();
+ for (CommandNode node : rootCommandNode.getChildren()) {
Expand Down Expand Up @@ -197,9 +194,9 @@
}

- private static <S> void fillUsableCommands(CommandNode<S> root, CommandNode<S> current, S source, Map<CommandNode<S>, CommandNode<S>> output) {
- for (CommandNode<S> commandNode : root.getChildren()) {
+ private static <S> void fillUsableCommands(java.util.Collection<CommandNode<S>> children, CommandNode<S> current, S source, Map<CommandNode<S>, CommandNode<S>> output) { // Paper - Perf: Async command map building; pass copy of children
+ for (CommandNode<S> commandNode : children) { // Paper - Perf: Async command map building; pass copy of children
+ private static <S> void fillUsableCommands(CommandNode<S> root, CommandNode<S> current, S source, Map<CommandNode<S>, CommandNode<S>> output) { // Paper - Perf: Async command map building; pass copy of children
+ synchronized (root.children) { // Paper - Perf: Async command map building
for (CommandNode<S> commandNode : root.getChildren()) {
+ // Paper start - Brigadier API
+ if (commandNode.clientNode != null) {
+ commandNode = commandNode.clientNode;
Expand Down Expand Up @@ -246,12 +243,11 @@
if (argumentBuilder.getRedirect() != null) {
argumentBuilder.redirect(output.get(argumentBuilder.getRedirect()));
}
@@ -418,7 +_,7 @@
output.put(commandNode, commandNode1);
current.addChild(commandNode1);
if (!commandNode.getChildren().isEmpty()) {
- fillUsableCommands(commandNode, commandNode1, source, output);
+ fillUsableCommands(commandNode.getChildren(), commandNode1, source, output); // Paper - Perf: Async command map building; pass copy of children
@@ -422,6 +_,7 @@
}
}
}
+ } // Paper - Perf: Async command map building
}

public static LiteralArgumentBuilder<CommandSourceStack> literal(String name) {
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