Make changes based on PR comments

api/src/main/java/com/velocitypowered/api/event/player/PlayerModInfoEvent.java

@@ -4,6 +4,9 @@ import com.google.common.base.Preconditions;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.util.ModInfo;
 
+/**
+ * This event is fired when the players ModInfo is changed.
+ */
 public final class PlayerModInfoEvent {
     private final Player player;
     private final ModInfo modInfo;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -145,9 +145,8 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
             player.getConnectedServer().getConnection().write(PluginMessageUtil.rewriteMCBrand(packet));
         } else if (player.getConnectedServer().isLegacyForge() && !player.getConnectedServer().hasCompletedJoin()) {
             if (packet.getChannel().equals(VelocityConstants.FORGE_LEGACY_HANDSHAKE_CHANNEL)) {
-                List<ModInfo.Mod> mods = PluginMessageUtil.readModList(packet);
+                if (!player.getModInfo().isPresent()) {
-                if (!mods.isEmpty()) {
+                    PluginMessageUtil.readModList(packet).ifPresent(mods -> player.setModInfo(new ModInfo("FML", mods)));
-                    player.setModInfo(new ModInfo("FML", mods));
                 }
                 
                 // Always forward the FML handshake to the remote server.

proxy/src/main/java/com/velocitypowered/proxy/protocol/util/PluginMessageUtil.java

@@ -4,6 +4,7 @@ import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 import com.velocitypowered.api.util.ModInfo;
+import com.velocitypowered.proxy.connection.VelocityConstants;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
@@ -13,6 +14,7 @@ import io.netty.buffer.Unpooled;
 import java.nio.charset.StandardCharsets;
 import java.util.Collection;
 import java.util.List;
+import java.util.Optional;
 
 public class PluginMessageUtil {
     public static final String BRAND_CHANNEL_LEGACY = "MC|Brand";
@@ -79,13 +81,17 @@ public class PluginMessageUtil {
         return newMsg;
     }
     
-    public static List<ModInfo.Mod> readModList(PluginMessage message) {
+    public static Optional<List<ModInfo.Mod>> readModList(PluginMessage message) {
-        List<ModInfo.Mod> mods = Lists.newArrayList();
+        Preconditions.checkNotNull(message, "message");
+        Preconditions.checkArgument(message.getChannel().equals(VelocityConstants.FORGE_LEGACY_HANDSHAKE_CHANNEL),
+                "message is not a FML HS plugin message");
         
         ByteBuf byteBuf = Unpooled.wrappedBuffer(message.getData());
+        try {
             byte discriminator = byteBuf.readByte();
             
             if (discriminator == 2) {
+                ImmutableList.Builder<ModInfo.Mod> mods = ImmutableList.builder();
                 int modCount = ProtocolUtils.readVarInt(byteBuf);
                 
                 for (int index = 0; index < modCount; index++) {
@@ -93,8 +99,13 @@ public class PluginMessageUtil {
                     String version = ProtocolUtils.readString(byteBuf);
                     mods.add(new ModInfo.Mod(id, version));
                 }
+                
+                return Optional.of(mods.build());
             }
             
-        return ImmutableList.copyOf(mods);
+            return Optional.empty();
+        } finally {
+            byteBuf.release();
+        }
     }
 }