Fix online mode no auth token dimension setting on login

core/src/main/java/org/geysermc/geyser/translator/protocol/java/JavaLoginTranslator.java

@@ -26,28 +26,25 @@
 package org.geysermc.geyser.translator.protocol.java;
 
 import net.kyori.adventure.key.Key;
-import org.geysermc.erosion.Constants;
-import org.geysermc.geyser.level.JavaDimension;
-import org.geysermc.geyser.util.MinecraftKey;
-import org.geysermc.mcprotocollib.protocol.data.game.entity.player.PlayerSpawnInfo;
-import org.geysermc.mcprotocollib.protocol.packet.common.serverbound.ServerboundCustomPayloadPacket;
-import org.geysermc.mcprotocollib.protocol.packet.ingame.clientbound.ClientboundLoginPacket;
-import org.cloudburstmc.math.vector.Vector3f;
 import org.cloudburstmc.protocol.bedrock.data.GameRuleData;
-import org.cloudburstmc.protocol.bedrock.data.LevelEvent;
 import org.cloudburstmc.protocol.bedrock.packet.GameRulesChangedPacket;
-import org.cloudburstmc.protocol.bedrock.packet.LevelEventPacket;
 import org.cloudburstmc.protocol.bedrock.packet.SetPlayerGameTypePacket;
+import org.geysermc.erosion.Constants;
 import org.geysermc.floodgate.pluginmessage.PluginMessageChannels;
 import org.geysermc.geyser.api.network.AuthType;
 import org.geysermc.geyser.entity.type.player.SessionPlayerEntity;
 import org.geysermc.geyser.erosion.GeyserboundHandshakePacketHandler;
+import org.geysermc.geyser.level.JavaDimension;
 import org.geysermc.geyser.session.GeyserSession;
 import org.geysermc.geyser.translator.protocol.PacketTranslator;
 import org.geysermc.geyser.translator.protocol.Translator;
 import org.geysermc.geyser.util.ChunkUtils;
 import org.geysermc.geyser.util.DimensionUtils;
 import org.geysermc.geyser.util.EntityUtils;
+import org.geysermc.geyser.util.MinecraftKey;
+import org.geysermc.mcprotocollib.protocol.data.game.entity.player.PlayerSpawnInfo;
+import org.geysermc.mcprotocollib.protocol.packet.common.serverbound.ServerboundCustomPayloadPacket;
+import org.geysermc.mcprotocollib.protocol.packet.ingame.clientbound.ClientboundLoginPacket;
 
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
@@ -83,6 +80,13 @@ public class JavaLoginTranslator extends PacketTranslator<ClientboundLoginPacket
             // Remove extra hearts, hunger, etc.
             entity.resetAttributes();
             entity.resetMetadata();
+        } else if (session.getUpstream().isInitialized()) {
+            if (newDimension.bedrockId() == 0) {
+                // A dimension switch will not happen, so make sure we initialized the dimension choice.
+                // Otherwise, the dimension switch will fill these values in.
+                session.setDimensionType(newDimension);
+                DimensionUtils.setBedrockDimension(session, newDimension.bedrockId());
+            }
         }
 
         session.setWorldName(spawnInfo.getWorldName());

core/src/main/java/org/geysermc/geyser/util/DimensionUtils.java

@@ -25,6 +25,7 @@
 
 package org.geysermc.geyser.util;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.cloudburstmc.math.vector.Vector3f;
 import org.cloudburstmc.math.vector.Vector3i;
 import org.cloudburstmc.protocol.bedrock.data.LevelEvent;
@@ -61,7 +62,7 @@ public class DimensionUtils {
     }
 
     public static void switchDimension(GeyserSession session, JavaDimension javaDimension, int bedrockDimension) {
-        JavaDimension previousDimension = session.getDimensionType(); // previous java dimension
+        @Nullable JavaDimension previousDimension = session.getDimensionType(); // previous java dimension; can be null if an online player with no saved auth token logs in.
 
         Entity player = session.getPlayerEntity();
 
@@ -109,7 +110,7 @@ public class DimensionUtils {
         if (isCustomBedrockNetherId()) {
             if (javaDimension.isNetherLike()) {
                 session.camera().sendFog(BEDROCK_FOG_HELL);
-            } else if (previousDimension.isNetherLike()) {
+            } else if (previousDimension != null && previousDimension.isNetherLike()) {
                 session.camera().removeFog(BEDROCK_FOG_HELL);
             }
         }