Default minecraft alias to redirect (#12146)

While the running server will still be using the recently introduced
copy-mechanic for vanilla command namespacing, the data converter logic
relies on the fact that namespaced aliases were redirects as well.

To not break the converted, the commands type now takes a modern flag
only set by the running server.

paper-server/patches/sources/net/minecraft/commands/Commands.java.patch

@@ -1,6 +1,18 @@
 --- a/net/minecraft/commands/Commands.java
 +++ b/net/minecraft/commands/Commands.java
-@@ -251,6 +_,24 @@
+@@ -150,6 +_,11 @@
+     private final CommandDispatcher<CommandSourceStack> dispatcher = new CommandDispatcher<>();
+
+     public Commands(Commands.CommandSelection selection, CommandBuildContext context) {
++    // Paper start - Brigadier API - modern minecraft overloads that do not use redirects but are copies instead
++        this(selection, context, false);
++    }
++    public Commands(Commands.CommandSelection selection, CommandBuildContext context, final boolean modern) {
++    // Paper end - Brigadier API - modern minecraft overloads that do not use redirects but are copies instead
+         AdvancementCommands.register(this.dispatcher);
+         AttributeCommand.register(this.dispatcher, context);
+         ExecuteCommand.register(this.dispatcher, context);
+@@ -251,6 +_,40 @@
              PublishCommand.register(this.dispatcher);
          }
 
@@ -14,12 +26,28 @@
 +        // Paper start - Brigadier Command API
 +        // Create legacy minecraft namespace commands
 +        for (final CommandNode<CommandSourceStack> node : new java.util.ArrayList<>(this.dispatcher.getRoot().getChildren())) {
-+            this.dispatcher.getRoot().addChild(
-+                io.papermc.paper.command.brigadier.PaperBrigadier.copyLiteral(
-+                    "minecraft:" + node.getName(),
-+                    (com.mojang.brigadier.tree.LiteralCommandNode<CommandSourceStack>) node
-+                )
-+            );
++            if (modern) {
++                // Modern behaviour that simply creates a full copy of the commands node.
++                // Avoids plenty of issues around registering redirects *to* these nodes from the API
++                this.dispatcher.getRoot().addChild(
++                    io.papermc.paper.command.brigadier.PaperBrigadier.copyLiteral(
++                        "minecraft:" + node.getName(),
++                        (com.mojang.brigadier.tree.LiteralCommandNode<CommandSourceStack>) node
++                    )
++                );
++                continue;
++            }
++
++            // Legacy behaviour of creating a flattened redirecting node.
++            // Used by CommandArgumentUpgrader
++            CommandNode<CommandSourceStack> flattenedAliasTarget = node;
++            while (flattenedAliasTarget.getRedirect() != null) flattenedAliasTarget = flattenedAliasTarget.getRedirect();
++
++            this.dispatcher.register(
++                com.mojang.brigadier.builder.LiteralArgumentBuilder.<CommandSourceStack>literal("minecraft:" + node.getName())
++                    .executes(flattenedAliasTarget.getCommand())
++                    .requires(flattenedAliasTarget.getRequirement())
++                    .redirect(flattenedAliasTarget));
 +        }
 +        // Paper end - Brigadier Command API
          this.dispatcher.setConsumer(ExecutionCommandSource.resultConsumer());

paper-server/patches/sources/net/minecraft/server/ReloadableServerResources.java.patch

@@ -1,9 +1,11 @@
 --- a/net/minecraft/server/ReloadableServerResources.java
 +++ b/net/minecraft/server/ReloadableServerResources.java
-@@ -39,6 +_,7 @@
+@@ -38,7 +_,8 @@
+         this.fullRegistryHolder = new ReloadableServerRegistries.Holder(registryAccess.compositeAccess());
          this.postponedTags = postponedTags;
          this.recipes = new RecipeManager(registries);
-         this.commands = new Commands(commandSelection, CommandBuildContext.simple(registries, enabledFeatures));
+-        this.commands = new Commands(commandSelection, CommandBuildContext.simple(registries, enabledFeatures));
++        this.commands = new Commands(commandSelection, CommandBuildContext.simple(registries, enabledFeatures), true); // Paper - Brigadier Command API - use modern alias registration
 +        io.papermc.paper.command.brigadier.PaperCommands.INSTANCE.setDispatcher(this.commands, CommandBuildContext.simple(registries, enabledFeatures)); // Paper - Brigadier Command API
          this.advancements = new ServerAdvancementManager(registries);
          this.functionLibrary = new ServerFunctionLibrary(functionCompilationLevel, this.commands.getDispatcher());

paper-server/src/test/java/io/papermc/paper/command/brigadier/DFUCommandArgumentUpgraderCompatTest.java

@@ -0,0 +1,17 @@
+package io.papermc.paper.command.brigadier;
+
+import ca.spottedleaf.dataconverter.util.CommandArgumentUpgrader;
+import org.bukkit.support.environment.Normal;
+import org.junit.jupiter.api.Test;
+
+@Normal
+public class DFUCommandArgumentUpgraderCompatTest {
+
+    @Test
+    public void testCompatibilityWithCommandArgumentUpgrader() {
+        // The Command argument upgrader has some specific assumptions about the tree, specifically around
+        // Attempt to construct it and to that degree its tree of commands.
+        CommandArgumentUpgrader.upgrader_1_20_4_to_1_20_5(999);
+    }
+
+}

paper-server/src/test/java/io/papermc/paper/permissions/MinecraftCommandPermissionsTest.java

@@ -40,7 +40,7 @@ public void test() {
         CraftDefaultPermissions.registerCorePermissions();
         Set<String> perms = collectMinecraftCommandPerms();
 
-        Commands commands = new Commands(Commands.CommandSelection.DEDICATED, CommandBuildContext.simple(RegistryHelper.getRegistry(), FeatureFlags.VANILLA_SET));
+        Commands commands = new Commands(Commands.CommandSelection.DEDICATED, CommandBuildContext.simple(RegistryHelper.getRegistry(), FeatureFlags.VANILLA_SET), true);
         RootCommandNode<CommandSourceStack> root = commands.getDispatcher().getRoot();
         Set<String> missing = new LinkedHashSet<>();
         Set<String> foundPerms = new HashSet<>();