Make Metadata fully type safe, remove "Discontinued" meta types

The Discontinued entry was a special edge case that could lead to a Metadata type returning null. Instead, just directly use null in the 1.8->1.9 code where it is checked against. Also renamed the Meta1_17Types entries to be in uppercase and properly represent their value type.

api/src/main/java/com/viaversion/viaversion/api/data/entity/EntityTracker.java

@@ -26,7 +26,7 @@ import com.viaversion.viaversion.api.connection.UserConnection;
 import com.viaversion.viaversion.api.minecraft.entities.EntityType;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
-public interface EntityTracker extends ClientEntityIdChangeListener {
+public interface EntityTracker {
 
     /**
      * User connection the tracker belongs to.

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/Metadata.java

@@ -38,14 +38,12 @@ public final class Metadata {
      * @param id       metadata index
      * @param metaType metadata type
      * @param value    value if present
-     * @throws NullPointerException     if the given metaType is null
      * @throws IllegalArgumentException if the value and metaType are incompatible
      */
     public Metadata(int id, MetaType metaType, @Nullable Object value) {
-        Preconditions.checkNotNull(metaType);
         this.id = id;
         this.metaType = metaType;
-        this.value = checkValue(value);
+        this.value = checkValue(metaType, value);
     }
 
     public int id() {
@@ -61,13 +59,14 @@ public final class Metadata {
     }
 
     /**
-     * Sets the metadata type.
+     * Sets the metadata type if compatible with the current value.
-     * Update the value with {@link #setValue(Object)} in case value and type are no longer compatible.
      *
      * @param metaType metadata type
+     * @throws IllegalArgumentException if the metadata type and current value are incompatible
+     * @see #setTypeAndValue(MetaType, Object)
      */
     public void setMetaType(MetaType metaType) {
-        Preconditions.checkNotNull(metaType);
+        checkValue(metaType, this.value);
         this.metaType = metaType;
     }
 
@@ -80,28 +79,46 @@ public final class Metadata {
     }
 
     /**
-     * Sets the metadata value.
+     * Sets the metadata value if compatible with the current meta type.
-     * Always call {@link #setMetaType(MetaType)} first if the output type changes.
      *
      * @param value value
-     * @throws IllegalArgumentException if the value and metaType are incompatible
+     * @throws IllegalArgumentException if the value and current metaType are incompatible
+     * @see #setTypeAndValue(MetaType, Object)
      */
     public void setValue(@Nullable Object value) {
-        this.value = checkValue(value);
+        this.value = checkValue(this.metaType, value);
     }
 
-    private Object checkValue(Object value) {
+    /**
+     * Sets metadata type and value.
+     *
+     * @param metaType metadata type
+     * @param value    value
+     * @throws IllegalArgumentException if the value and metaType are incompatible
+     */
+    public void setTypeAndValue(MetaType metaType, @Nullable Object value) {
+        this.value = checkValue(metaType, value);
+        this.metaType = metaType;
+    }
+
+    private Object checkValue(MetaType metaType, @Nullable Object value) {
+        Preconditions.checkNotNull(metaType);
         if (value != null && !metaType.type().getOutputClass().isAssignableFrom(value.getClass())) {
-            throw new IllegalArgumentException("Metadata value and metaType are incompatible. Type=" + metaType + ", value=" + value);
+            throw new IllegalArgumentException("Metadata value and metaType are incompatible. Type=" + metaType
+                    + ", value=" + (value != null ? value + " (" + value.getClass().getSimpleName() + ")" : "null"));
         }
         return value;
     }
 
+    @Deprecated
+    public void setMetaTypeUnsafe(MetaType type) {
+        this.metaType = type;
+    }
+
     @Override
     public boolean equals(final Object o) {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
-
         Metadata metadata = (Metadata) o;
         if (id != metadata.id) return false;
         if (metaType != metaType) return false;
@@ -111,7 +128,7 @@ public final class Metadata {
     @Override
     public int hashCode() {
         int result = id;
-        result = 31 * result + (metaType != null ? metaType.hashCode() : 0);
+        result = 31 * result + metaType.hashCode();
         result = 31 * result + (value != null ? value.hashCode() : 0);
         return result;
     }

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_12.java

@@ -39,8 +39,7 @@ public enum MetaType1_12 implements MetaType {
     Direction(10, Type.VAR_INT),
     OptUUID(11, Type.OPTIONAL_UUID),
     BlockID(12, Type.VAR_INT),
-    NBTTag(13, Type.NBT),
+    NBTTag(13, Type.NBT);
-    Discontinued(99, null);
 
     private final int typeID;
     private final Type type;

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_13.java

@@ -42,8 +42,7 @@ public enum MetaType1_13 implements MetaType {
     OptUUID(12, Type.OPTIONAL_UUID),
     BlockID(13, Type.VAR_INT),
     NBTTag(14, Type.NBT),
-    PARTICLE(15, Types1_13.PARTICLE),
+    PARTICLE(15, Types1_13.PARTICLE);
-    Discontinued(99, null);
 
     private final int typeID;
     private final Type type;

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_13_2.java

@@ -42,8 +42,7 @@ public enum MetaType1_13_2 implements MetaType {
     OptUUID(12, Type.OPTIONAL_UUID),
     BlockID(13, Type.VAR_INT),
     NBTTag(14, Type.NBT),
-    PARTICLE(15, Types1_13_2.PARTICLE),
+    PARTICLE(15, Types1_13_2.PARTICLE);
-    Discontinued(99, null);
 
     private final int typeID;
     private final Type type;

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_14.java

@@ -45,8 +45,7 @@ public enum MetaType1_14 implements MetaType {
     PARTICLE(15, Types1_14.PARTICLE),
     VillagerData(16, Type.VILLAGER_DATA),
     OptVarInt(17, Type.OPTIONAL_VAR_INT),
-    Pose(18, Type.VAR_INT),
+    Pose(18, Type.VAR_INT);
-    Discontinued(99, null);
 
     private final int typeID;
     private final Type type;

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_17.java

@@ -27,32 +27,31 @@ import com.viaversion.viaversion.api.type.Type;
 import com.viaversion.viaversion.api.type.types.version.Types1_17;
 
 public enum MetaType1_17 implements MetaType {
-    Byte(0, Type.BYTE),
+    BYTE(0, Type.BYTE),
-    VarInt(1, Type.VAR_INT),
+    VAR_INT(1, Type.VAR_INT),
-    Float(2, Type.FLOAT),
+    FLOAT(2, Type.FLOAT),
-    String(3, Type.STRING),
+    STRING(3, Type.STRING),
-    Chat(4, Type.COMPONENT),
+    COMPONENT(4, Type.COMPONENT),
-    OptChat(5, Type.OPTIONAL_COMPONENT),
+    OPT_COMPONENT(5, Type.OPTIONAL_COMPONENT),
-    Slot(6, Type.FLAT_VAR_INT_ITEM),
+    ITEM(6, Type.FLAT_VAR_INT_ITEM),
-    Boolean(7, Type.BOOLEAN),
+    BOOLEAN(7, Type.BOOLEAN),
-    Vector3F(8, Type.ROTATION),
+    ROTATION(8, Type.ROTATION),
-    Position(9, Type.POSITION1_14),
+    POSITION(9, Type.POSITION1_14),
-    OptPosition(10, Type.OPTIONAL_POSITION_1_14),
+    OPT_POSITION(10, Type.OPTIONAL_POSITION_1_14),
-    Direction(11, Type.VAR_INT),
+    DIRECTION(11, Type.VAR_INT),
-    OptUUID(12, Type.OPTIONAL_UUID),
+    OPT_UUID(12, Type.OPTIONAL_UUID),
-    BlockID(13, Type.VAR_INT),
+    BLOCK_STATE(13, Type.VAR_INT),
-    NBTTag(14, Type.NBT),
+    NBT(14, Type.NBT),
     PARTICLE(15, Types1_17.PARTICLE),
-    VillagerData(16, Type.VILLAGER_DATA),
+    VILLAGER_DATA(16, Type.VILLAGER_DATA),
-    OptVarInt(17, Type.OPTIONAL_VAR_INT),
+    OPT_VAR_INT(17, Type.OPTIONAL_VAR_INT),
-    Pose(18, Type.VAR_INT),
+    POSE(18, Type.VAR_INT);
-    Discontinued(99, null);
 
-    private final int typeID;
+    private final int typeId;
     private final Type type;
 
-    MetaType1_17(int typeID, Type type) {
+    MetaType1_17(int typeId, Type type) {
-        this.typeID = typeID;
+        this.typeId = typeId;
         this.type = type;
     }
 
@@ -62,7 +61,7 @@ public enum MetaType1_17 implements MetaType {
 
     @Override
     public int typeId() {
-        return typeID;
+        return typeId;
     }
 
     @Override

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_8.java

@@ -34,6 +34,7 @@ public enum MetaType1_8 implements MetaType {
     Slot(5, Type.ITEM),
     Position(6, Type.VECTOR),
     Rotation(7, Type.ROTATION),
+    @Deprecated
     NonExistent(-1, Type.NOTHING);
 
     private final int typeID;

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_9.java

@@ -38,8 +38,7 @@ public enum MetaType1_9 implements MetaType {
     OptPosition(9, Type.OPTIONAL_POSITION),
     Direction(10, Type.VAR_INT),
     OptUUID(11, Type.OPTIONAL_UUID),
-    BlockID(12, Type.VAR_INT),
+    BlockID(12, Type.VAR_INT);
-    Discontinued(99, null);
 
     private final int typeID;
     private final Type type;

common/src/main/java/com/viaversion/viaversion/data/entity/EntityTrackerBase.java

@@ -20,6 +20,7 @@ package com.viaversion.viaversion.data.entity;
 
 import com.google.common.base.Preconditions;
 import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.data.entity.ClientEntityIdChangeListener;
 import com.viaversion.viaversion.api.data.entity.EntityTracker;
 import com.viaversion.viaversion.api.data.entity.StoredEntityData;
 import com.viaversion.viaversion.api.minecraft.entities.EntityType;
@@ -28,7 +29,7 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
-public class EntityTrackerBase implements EntityTracker {
+public class EntityTrackerBase implements EntityTracker, ClientEntityIdChangeListener {
     private final Map<Integer, EntityType> entityTypes = new ConcurrentHashMap<>();
     private final Map<Integer, StoredEntityData> entityData;
     private final UserConnection connection;
@@ -68,9 +69,9 @@ public class EntityTrackerBase implements EntityTracker {
     }
 
     @Override
-    public StoredEntityData entityData(int id) {
+    public @Nullable StoredEntityData entityData(int id) {
         EntityType type = entityType(id);
-        return entityData.computeIfAbsent(id, s -> new StoredEntityImpl(type));
+        return type != null ? entityData.computeIfAbsent(id, s -> new StoredEntityImpl(type)) : null;
     }
 
     @Override

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_11to1_10/metadata/MetadataRewriter1_11To1_10.java

@@ -51,9 +51,8 @@ public class MetadataRewriter1_11To1_10 extends EntityRewriter<Protocol1_11To1_1
         if (type.is(EntityType.ELDER_GUARDIAN) || type.is(EntityType.GUARDIAN)) { // Guardians
             int oldid = metadata.id();
             if (oldid == 12) {
-                metadata.setMetaType(MetaType1_9.Boolean);
                 boolean val = (((byte) metadata.getValue()) & 0x02) == 0x02;
-                metadata.setValue(val);
+                metadata.setTypeAndValue(MetaType1_9.Boolean, val);
             }
         }
 

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_13to1_12_2/metadata/MetadataRewriter1_13To1_12_2.java

@@ -51,11 +51,10 @@ public class MetadataRewriter1_13To1_12_2 extends EntityRewriter<Protocol1_13To1
 
         // Handle String -> Chat DisplayName
         if (metadata.id() == 2) {
-            metadata.setMetaType(MetaType1_13.OptChat);
             if (metadata.getValue() != null && !((String) metadata.getValue()).isEmpty()) {
-                metadata.setValue(ChatRewriter.legacyTextToJson((String) metadata.getValue()));
+                metadata.setTypeAndValue(MetaType1_13.OptChat, ChatRewriter.legacyTextToJson((String) metadata.getValue()));
             } else {
-                metadata.setValue(null);
+                metadata.setTypeAndValue(MetaType1_13.OptChat, null);
             }
         }
 

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_14to1_13_2/metadata/MetadataRewriter1_14To1_13_2.java

@@ -139,14 +139,12 @@ public class MetadataRewriter1_14To1_13_2 extends EntityRewriter<Protocol1_14To1
         } else if (type.is(Entity1_14Types.VILLAGER)) {
             if (metadata.id() == 15) {
                 // plains
-                metadata.setMetaType(MetaType1_14.VillagerData);
+                metadata.setTypeAndValue(MetaType1_14.VillagerData, new VillagerData(2, getNewProfessionId((int) metadata.getValue()), 0));
-                metadata.setValue(new VillagerData(2, getNewProfessionId((int) metadata.getValue()), 0));
             }
         } else if (type.is(Entity1_14Types.ZOMBIE_VILLAGER)) {
             if (metadata.id() == 18) {
                 // plains
-                metadata.setMetaType(MetaType1_14.VillagerData);
+                metadata.setTypeAndValue(MetaType1_14.VillagerData, new VillagerData(2, getNewProfessionId((int) metadata.getValue()), 0));
-                metadata.setValue(new VillagerData(2, getNewProfessionId((int) metadata.getValue()), 0));
             }
         } else if (type.isOrHasParent(Entity1_14Types.ABSTRACT_ARROW)) {
             if (metadata.id() >= 9) { // New piercing

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_17to1_16_4/metadata/MetadataRewriter1_17To1_16_4.java

@@ -37,7 +37,7 @@ public class MetadataRewriter1_17To1_16_4 extends EntityRewriter {
         filter().handler((event, meta) -> {
             meta.setMetaType(MetaType1_17.byId(meta.metaType().typeId()));
 
-            if (meta.metaType() == MetaType1_17.Pose) {
+            if (meta.metaType() == MetaType1_17.POSE) {
                 int pose = meta.value();
                 if (pose > 5) {
                     // Added LONG_JUMP at 6
@@ -45,7 +45,7 @@ public class MetadataRewriter1_17To1_16_4 extends EntityRewriter {
                 }
             }
         });
-        registerDumMetaTypeHandler(MetaType1_17.Slot, MetaType1_17.BlockID, MetaType1_17.PARTICLE, InventoryPackets::toClient);
+        registerDumMetaTypeHandler(MetaType1_17.ITEM, MetaType1_17.BLOCK_STATE, MetaType1_17.PARTICLE, InventoryPackets::toClient);
 
         // Ticks frozen added with id 7
         filter().filterFamily(Entity1_17Types.ENTITY).addIndex(7);

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_9to1_8/metadata/MetaIndex.java

@@ -22,6 +22,7 @@ import com.viaversion.viaversion.api.minecraft.entities.EntityType;
 import com.viaversion.viaversion.api.minecraft.metadata.types.MetaType1_8;
 import com.viaversion.viaversion.api.minecraft.metadata.types.MetaType1_9;
 import com.viaversion.viaversion.util.Pair;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.HashMap;
 import java.util.Optional;
@@ -54,11 +55,11 @@ public enum MetaIndex {
     STAND_RL_POS(ARMOR_STAND, 16, MetaType1_8.Rotation, MetaType1_9.Vector3F),
     // human, discountined?
     PLAYER_SKIN_FLAGS(ENTITY_HUMAN, 10, MetaType1_8.Byte, 12, MetaType1_9.Byte), // unsigned on 1.8
-    PLAYER_HUMAN_BYTE(ENTITY_HUMAN, 16, MetaType1_8.Byte, MetaType1_9.Discontinued), // unused on 1.8
+    PLAYER_HUMAN_BYTE(ENTITY_HUMAN, 16, MetaType1_8.Byte, null), // unused on 1.8
     PLAYER_ADDITIONAL_HEARTS(ENTITY_HUMAN, 17, MetaType1_8.Float, 10, MetaType1_9.Float),
     PLAYER_SCORE(ENTITY_HUMAN, 18, MetaType1_8.Int, 11, MetaType1_9.VarInt),
     PLAYER_HAND(ENTITY_HUMAN, -1, MetaType1_8.NonExistent, 5, MetaType1_9.Byte), // new in 1.9
-    SOMETHING_ANTICHEAT_PLUGINS_FOR_SOME_REASON_USE(ENTITY_HUMAN, 11, MetaType1_8.Byte, MetaType1_9.Discontinued), //For what we know, This doesn't exists. If you think it exists and knows what it does. Please tell us.
+    SOMETHING_ANTICHEAT_PLUGINS_FOR_SOME_REASON_USE(ENTITY_HUMAN, 11, MetaType1_8.Byte, null), //For what we know, This doesn't exists. If you think it exists and knows what it does. Please tell us.
     // horse
     HORSE_INFO(HORSE, 16, MetaType1_8.Int, 12, MetaType1_9.Byte),
     HORSE_TYPE(HORSE, 19, MetaType1_8.Byte, 13, MetaType1_9.VarInt),
@@ -86,7 +87,7 @@ public enum MetaIndex {
     VILLAGER_PROFESSION(VILLAGER, 16, MetaType1_8.Int, 12, MetaType1_9.VarInt),
     // enderman
     ENDERMAN_BLOCKSTATE(ENDERMAN, 16, MetaType1_8.Short, 11, MetaType1_9.BlockID),
-    ENDERMAN_BLOCKDATA(ENDERMAN, 17, MetaType1_8.Byte, MetaType1_9.Discontinued), //always 0 when sent, never read by the client
+    ENDERMAN_BLOCKDATA(ENDERMAN, 17, MetaType1_8.Byte, null), //always 0 when sent, never read by the client
     ENDERMAN_ISSCREAMING(ENDERMAN, 18, MetaType1_8.Byte, 12, MetaType1_9.Boolean),
     // zombie
     ZOMBIE_ISCHILD(ZOMBIE, 12, MetaType1_8.Byte, 11, MetaType1_9.Boolean),
@@ -117,7 +118,7 @@ public enum MetaIndex {
     WITHER_TARGET3(WITHER, 19, MetaType1_8.Int, 13, MetaType1_9.VarInt),
     WITHER_INVULN_TIME(WITHER, 20, MetaType1_8.Int, 14, MetaType1_9.VarInt),
     WITHER_PROPERTIES(WITHER, 10, MetaType1_8.Byte, MetaType1_9.Byte),
-    WITHER_UNKNOWN(WITHER, 11, MetaType1_8.Byte, MetaType1_9.Discontinued),
+    WITHER_UNKNOWN(WITHER, 11, MetaType1_8.Byte, null),
     // wither skull
     WITHERSKULL_INVULN(WITHER_SKULL, 10, MetaType1_8.Byte, 5, MetaType1_9.Boolean),
     // guardian
@@ -150,12 +151,12 @@ public enum MetaIndex {
     ITEMFRAME_ITEM(ITEM_FRAME, 8, MetaType1_8.Slot, 5, MetaType1_9.Slot),
     ITEMFRAME_ROTATION(ITEM_FRAME, 9, MetaType1_8.Byte, 6, MetaType1_9.VarInt),
     // ender crystal
-    ENDERCRYSTAL_HEALTH(ENDER_CRYSTAL, 8, MetaType1_8.Int, MetaType1_9.Discontinued),
+    ENDERCRYSTAL_HEALTH(ENDER_CRYSTAL, 8, MetaType1_8.Int, null),
     // Ender dragon boss bar issues
-    ENDERDRAGON_UNKNOWN(ENDER_DRAGON, 5, MetaType1_8.Byte, MetaType1_9.Discontinued),
+    ENDERDRAGON_UNKNOWN(ENDER_DRAGON, 5, MetaType1_8.Byte, null),
-    ENDERDRAGON_NAME(ENDER_DRAGON, 10, MetaType1_8.String, MetaType1_9.Discontinued),
+    ENDERDRAGON_NAME(ENDER_DRAGON, 10, MetaType1_8.String, null),
     // Normal Ender dragon
-    ENDERDRAGON_FLAG(ENDER_DRAGON, 15, MetaType1_8.Byte, MetaType1_9.Discontinued),
+    ENDERDRAGON_FLAG(ENDER_DRAGON, 15, MetaType1_8.Byte, null),
     ENDERDRAGON_PHASE(ENDER_DRAGON, 11, MetaType1_8.Byte, MetaType1_9.VarInt);
 
     private static final HashMap<Pair<Entity1_10Types.EntityType, Integer>, MetaIndex> metadataRewrites = new HashMap<>();
@@ -171,7 +172,7 @@ public enum MetaIndex {
     private final MetaType1_8 oldType;
     private final int index;
 
-    MetaIndex(Entity1_10Types.EntityType type, int index, MetaType1_8 oldType, MetaType1_9 newType) {
+    MetaIndex(Entity1_10Types.EntityType type, int index, MetaType1_8 oldType, @Nullable MetaType1_9 newType) {
         this.clazz = type;
         this.index = index;
         this.newIndex = index;
@@ -179,7 +180,7 @@ public enum MetaIndex {
         this.newType = newType;
     }
 
-    MetaIndex(Entity1_10Types.EntityType type, int index, MetaType1_8 oldType, int newIndex, MetaType1_9 newType) {
+    MetaIndex(Entity1_10Types.EntityType type, int index, MetaType1_8 oldType, int newIndex, @Nullable MetaType1_9 newType) {
         this.clazz = type;
         this.index = index;
         this.oldType = oldType;
@@ -195,7 +196,7 @@ public enum MetaIndex {
         return newIndex;
     }
 
-    public MetaType1_9 getNewType() {
+    public @Nullable MetaType1_9 getNewType() {
         return newType;
     }
 

common/src/main/java/com/viaversion/viaversion/protocols/protocol1_9to1_8/metadata/MetadataRewriter1_9To1_8.java

@@ -26,7 +26,6 @@ import com.viaversion.viaversion.api.minecraft.item.Item;
 import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
 import com.viaversion.viaversion.api.minecraft.metadata.Metadata;
 import com.viaversion.viaversion.api.minecraft.metadata.types.MetaType1_8;
-import com.viaversion.viaversion.api.minecraft.metadata.types.MetaType1_9;
 import com.viaversion.viaversion.protocols.protocol1_9to1_8.ItemRewriter;
 import com.viaversion.viaversion.protocols.protocol1_9to1_8.Protocol1_9To1_8;
 import com.viaversion.viaversion.rewriter.EntityRewriter;
@@ -47,13 +46,13 @@ public class MetadataRewriter1_9To1_8 extends EntityRewriter<Protocol1_9To1_8> {
             throw new Exception("Could not find valid metadata");
         }
 
-        if (metaIndex.getNewType() == MetaType1_9.Discontinued) {
+        if (metaIndex.getNewType() == null) {
             metadatas.remove(metadata);
             return;
         }
 
         metadata.setId(metaIndex.getNewIndex());
-        metadata.setMetaType(metaIndex.getNewType());
+        metadata.setMetaTypeUnsafe(metaIndex.getNewType());
 
         Object value = metadata.getValue();
         switch (metaIndex.getNewType()) {