Wrap mod command argument types in proxy environment

src/mixins/java/org/spongepowered/common/mixin/ipforward/network/protocol/game/ClientboundCommandsPacket_ArgumentNodeStub_IpForward.java

@@ -0,0 +1,88 @@
+/*
+ * 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.mixin.ipforward.network.protocol.game;
+
+import com.mojang.brigadier.arguments.ArgumentType;
+import io.netty.buffer.Unpooled;
+import net.minecraft.commands.synchronization.ArgumentTypeInfo;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.resources.ResourceLocation;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/**
+ * If a proxy server tries to inspect the commands sent
+ * to the client, it is unable to parse the elements
+ * that contain mod specific information due to being
+ * unaware of their structure.
+ *
+ * To fix this, the proxy server expects that non-vanilla
+ * elements are wrapped in a magic argument that it can
+ * detect to skip its content.
+ *
+ * The proxy server is expected to unwrap these arguments
+ * afterward to allow the client to parse the commands
+ * as normal.
+ */
+@Mixin(targets = "net/minecraft/network/protocol/game/ClientboundCommandsPacket$ArgumentNodeStub")
+public final class ClientboundCommandsPacket_ArgumentNodeStub_IpForward {
+
+    //Magic value that was chosen by the proxy implementation.
+    private static final int ipForward$MOD_ARGUMENT_ID = -256;
+
+    @Inject(method = "serializeCap(Lnet/minecraft/network/FriendlyByteBuf;Lnet/minecraft/commands/synchronization/ArgumentTypeInfo;Lnet/minecraft/commands/synchronization/ArgumentTypeInfo$Template;)V", at = @At("HEAD"), cancellable = true)
+    private static <A extends ArgumentType<?>, T extends ArgumentTypeInfo.Template<A>> void ipForward$onSerializeCap(
+        final FriendlyByteBuf buf, final ArgumentTypeInfo<A, T> $$1, final ArgumentTypeInfo.Template<A> $$2, final CallbackInfo ci) {
+        final @Nullable ResourceLocation key = BuiltInRegistries.COMMAND_ARGUMENT_TYPE.getKey($$1);
+        if (key == null || ClientboundCommandsPacket_ArgumentNodeStub_IpForward.ipForward$isVanillaArgument(key)) {
+            return;
+        }
+
+        ci.cancel();
+
+        final FriendlyByteBuf commandData = new FriendlyByteBuf(Unpooled.buffer());
+        $$1.serializeToNetwork((T) $$2, commandData);
+
+        buf.writeVarInt(ClientboundCommandsPacket_ArgumentNodeStub_IpForward.ipForward$MOD_ARGUMENT_ID);
+        buf.writeVarInt(BuiltInRegistries.COMMAND_ARGUMENT_TYPE.getId($$1));
+        buf.writeVarInt(commandData.readableBytes());
+        buf.writeBytes(commandData);
+    }
+
+    private static boolean ipForward$isVanillaArgument(final ResourceLocation key) {
+        return switch (key.getNamespace()) {
+            case "brigadier" -> true;
+            case "minecraft" -> switch (key.getPath()) {
+                case "test_argument", "test_class" -> false; //These are normally under IS_RUNNING_IN_IDE, proxies cant handle them.
+                default -> true;
+            };
+            default -> false;
+        };
+    }
+}

src/mixins/resources/mixins.sponge.ipforward.json

@@ -4,6 +4,7 @@
     "plugin": "org.spongepowered.common.mixin.plugin.IpForwardPlugin",
     "mixins": [
         "network.ConnectionMixin_IpForward",
+        "network.protocol.game.ClientboundCommandsPacket_ArgumentNodeStub_IpForward",
         "network.protocol.handshake.ClientIntentionPacketMixin_IpForward",
         "server.MinecraftServerMixin_IpForward",
         "server.network.ServerHandshakePacketListenerImplMixin_IpForward",