Make clearer distinction between filled and empty data component patch, simplify direct value getting

api/src/main/java/com/viaversion/viaversion/api/minecraft/data/StructuredData.java

@@ -52,16 +52,14 @@ public interface StructuredData<T> extends IdHolder {
         return new EmptyStructuredData<>(key, id);
     }
 
-    void setValue(final T value);
+    @Nullable T value();
 
-    void write(final ByteBuf buffer);
+    void setValue(final T value);
 
     void setId(final int id);
 
     StructuredDataKey<T> key();
 
-    @Nullable T value();
-
     /**
      * Returns whether the structured data is present. Even if true, the value may be null.
      *
@@ -77,4 +75,6 @@ public interface StructuredData<T> extends IdHolder {
      * @return true if the structured data is empty
      */
     boolean isEmpty();
+
+    void write(final ByteBuf buffer);
 }

api/src/main/java/com/viaversion/viaversion/api/minecraft/data/StructuredDataContainer.java

@@ -33,6 +33,26 @@ import java.util.Map;
 import java.util.function.Function;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
+/**
+ * Loosely represents Minecraft's data component patch, but may also be used for an item's full data components.
+ * <p>
+ * The most commonly used methods will ignore empty data (aka empty overrides that remove item defaults) since those will rarely be needed.
+ * These are:
+ * <ul>
+ *     <li>{@link #get(StructuredDataKey)}</li>
+ *     <li>{@link #set(StructuredDataKey, Object)}</li>
+ *     <li>{@link #set(StructuredDataKey)}</li>
+ *     <li>{@link #getNonEmptyData(StructuredDataKey)}</li>
+ *     <li>{@link #hasValue(StructuredDataKey)}</li>
+ * </ul>
+ *
+ * To interact with empty patches specifically, use:
+ * <ul>
+ *     <li>{@link #setEmpty(StructuredDataKey)}</li>
+ *     <li>{@link #hasEmpty(StructuredDataKey)}</li>
+ * </ul>
+ * Other methods (e.g. {@link #getData(StructuredDataKey)} and {@link #has(StructuredDataKey)}) will handle both empty and non-empty data.
+ */
 public final class StructuredDataContainer {
 
     private final Map<StructuredDataKey<?>, StructuredData<?>> data;
@@ -55,66 +75,45 @@ public final class StructuredDataContainer {
     }
 
     /**
-     * Returns structured data by id if present.
+     * Returns the non-empty value by id if present.
+     *
+     * @param key serializer id
+     * @param <T> data type
+     * @return structured data
+     * @see #hasEmpty(StructuredDataKey)
+     */
+    public @Nullable <T> T get(final StructuredDataKey<T> key) {
+        final StructuredData<?> data = this.data.get(key);
+        if (data == null || data.isEmpty()) {
+            return null;
+        }
+        //noinspection unchecked
+        return ((StructuredData<T>) data).value();
+    }
+
+    /**
+     * Returns structured data by id if present, either empty or non-empty.
      *
      * @param key serializer id
      * @param <T> data type
      * @return structured data
      */
-    public @Nullable <T> StructuredData<T> get(final StructuredDataKey<T> key) {
+    public @Nullable <T> StructuredData<T> getData(final StructuredDataKey<T> key) {
         //noinspection unchecked
         return (StructuredData<T>) this.data.get(key);
     }
 
     /**
-     * Returns structured data by id if not empty.
+     * Returns non-empty structured data by id if present.
      *
      * @param key serializer id
      * @param <T> data type
-     * @return structured data if not empty
+     * @return non-empty structured data
      */
-    public @Nullable <T> StructuredData<T> getNonEmpty(final StructuredDataKey<T> key) {
+    public @Nullable <T> StructuredData<T> getNonEmptyData(final StructuredDataKey<T> key) {
+        final StructuredData<?> data = this.data.get(key);
         //noinspection unchecked
-        final StructuredData<T> data = (StructuredData<T>) this.data.get(key);
+        return data != null && data.isPresent() ? (StructuredData<T>) data : null;
-        return data != null && data.isPresent() ? data : null;
-    }
-
-    /**
-     * Returns structured data by id if not empty, or creates it.
-     *
-     * @param key             serializer id
-     * @param mappingFunction function to create structured data if not present
-     * @param <T>             data type
-     * @return structured data if not empty
-     */
-    public <T> StructuredData<T> computeIfAbsent(final StructuredDataKey<T> key, final Function<StructuredDataKey<T>, T> mappingFunction) {
-        final StructuredData<T> data = this.getNonEmpty(key);
-        if (data != null) {
-            return data;
-        }
-
-        final int id = serializerId(key);
-        final StructuredData<T> empty = StructuredData.of(key, mappingFunction.apply(key), id);
-        this.data.put(key, empty);
-        return empty;
-    }
-
-    /**
-     * Updates and returns the structured data by id if not empty.
-     *
-     * @param key             serializer id
-     * @param mappingFunction function to update existing data
-     * @param <T>             data type
-     * @return updated structured data if not empty
-     */
-    public <T> @Nullable StructuredData<T> updateIfPresent(final StructuredDataKey<T> key, final Function<T, T> mappingFunction) {
-        final StructuredData<T> data = this.getNonEmpty(key);
-        if (data == null) {
-            return null;
-        }
-
-        data.setValue(mappingFunction.apply(data.value()));
-        return data;
     }
 
     public <T> void set(final StructuredDataKey<T> key, final T value) {
@@ -124,49 +123,105 @@ public final class StructuredDataContainer {
         }
     }
 
-    public <T> void replaceKey(final StructuredDataKey<T> key, final StructuredDataKey<T> toKey) {
-        replace(key, toKey, Function.identity());
-    }
-
-    public <T, V> void replace(final StructuredDataKey<T> key, final StructuredDataKey<V> toKey, final Function<T, V> valueMapper) {
-        final StructuredData<T> data = remove(key);
-        if (data == null) {
-            return;
-        }
-
-        if (data.isPresent()) {
-            set(toKey, valueMapper.apply(data.value()));
-        } else {
-            addEmpty(toKey);
-        }
-    }
-
     public void set(final StructuredDataKey<Unit> key) {
         this.set(key, Unit.INSTANCE);
     }
 
-    public void addEmpty(final StructuredDataKey<?> key) {
+    public void setEmpty(final StructuredDataKey<?> key) {
         // Empty optional to override the Minecraft default
         this.data.put(key, StructuredData.empty(key, serializerId(key)));
     }
 
     /**
-     * Removes and returns structured data by the given key.
+     * Updates the structured data by id if not empty.
      *
-     * @param key serializer key
+     * @param key         serializer id
+     * @param valueMapper function to update existing data
      * @param <T>         data type
-     * @return removed structured data
      */
-    public @Nullable <T> StructuredData<T> remove(final StructuredDataKey<T> key) {
+    public <T> void replace(final StructuredDataKey<T> key, final Function<T, @Nullable T> valueMapper) {
-        final StructuredData<?> data = this.data.remove(key);
+        final StructuredData<T> data = this.getNonEmptyData(key);
-        //noinspection unchecked
+        if (data == null) {
-        return data != null ? (StructuredData<T>) data : null;
+            return;
         }
 
-    public boolean contains(final StructuredDataKey<?> key) {
+        final T replacement = valueMapper.apply(data.value());
+        if (replacement != null) {
+            data.setValue(replacement);
+        } else {
+            this.data.remove(key);
+        }
+    }
+
+    public <T> void replaceKey(final StructuredDataKey<T> key, final StructuredDataKey<T> toKey) {
+        replace(key, toKey, Function.identity());
+    }
+
+    public <T, V> void replace(final StructuredDataKey<T> key, final StructuredDataKey<V> toKey, final Function<T, @Nullable V> valueMapper) {
+        final StructuredData<?> data = this.data.remove(key);
+        if (data == null) {
+            return;
+        }
+
+        if (data.isPresent()) {
+            //noinspection unchecked
+            final T value = (T) data.value();
+            final V replacement = valueMapper.apply(value);
+            if (replacement != null) {
+                set(toKey, replacement);
+            }
+        } else {
+            // Also replace the key for empty data
+            setEmpty(toKey);
+        }
+    }
+
+    /**
+     * Removes data by the given key.
+     *
+     * @param key data key
+     * @see #replace(StructuredDataKey, Function)
+     * @see #replace(StructuredDataKey, StructuredDataKey, Function)
+     * @see #replaceKey(StructuredDataKey, StructuredDataKey)
+     */
+    public void remove(final StructuredDataKey<?> key) {
+        this.data.remove(key);
+    }
+
+    /**
+     * Returns whether there is data for the given key, either empty or non-empty.
+     *
+     * @param key data key
+     * @return whether there data for the given key
+     * @see #hasEmpty(StructuredDataKey)
+     * @see #hasValue(StructuredDataKey)
+     */
+    public boolean has(final StructuredDataKey<?> key) {
         return this.data.containsKey(key);
     }
 
+    /**
+     * Returns whether there is non-empty data for the given key.
+     *
+     * @param key data key
+     * @return whether there is non-empty data for the given key
+     */
+    public boolean hasValue(final StructuredDataKey<?> key) {
+        final StructuredData<?> data = this.data.get(key);
+        return data != null && data.isPresent();
+    }
+
+    /**
+     * Returns whether the structured data has an empty patch/override.
+     *
+     * @param key serializer id
+     * @return whether the structured data has an empty patch/override
+     */
+    public boolean hasEmpty(final StructuredDataKey<?> key) {
+        final StructuredData<?> data = this.data.get(key);
+        return data != null && data.isEmpty();
+    }
+
     /**
      * Sets the lookup for serializer ids. Required to call most of the other methods.
      *

common/src/main/java/com/viaversion/viaversion/protocols/v1_20_3to1_20_5/rewriter/BlockItemPacketRewriter1_20_5.java

@@ -416,7 +416,7 @@ public final class BlockItemPacketRewriter1_20_5 extends ItemRewriter<Clientboun
         final StructuredDataContainer data = item.dataContainer();
         data.setIdLookup(protocol, true);
 
-        final StructuredData<CompoundTag> customData = data.getNonEmpty(StructuredDataKey.CUSTOM_DATA);
+        final StructuredData<CompoundTag> customData = data.getNonEmptyData(StructuredDataKey.CUSTOM_DATA);
         final CompoundTag tag = customData != null ? customData.value() : new CompoundTag();
         final DataItem dataItem = new DataItem(item.identifier(), (byte) item.amount(), tag);
         if (!dataConverter.backupInconvertibleData() && customData != null && tag.remove(nbtTagName()) != null) {

common/src/main/java/com/viaversion/viaversion/protocols/v1_20_5to1_21/rewriter/BlockItemPacketRewriter1_21.java

@@ -20,7 +20,6 @@ package com.viaversion.viaversion.protocols.v1_20_5to1_21.rewriter;
 import com.viaversion.nbt.tag.ByteTag;
 import com.viaversion.nbt.tag.CompoundTag;
 import com.viaversion.viaversion.api.connection.UserConnection;
-import com.viaversion.viaversion.api.minecraft.data.StructuredData;
 import com.viaversion.viaversion.api.minecraft.data.StructuredDataContainer;
 import com.viaversion.viaversion.api.minecraft.data.StructuredDataKey;
 import com.viaversion.viaversion.api.minecraft.item.Item;
@@ -123,7 +122,7 @@ public final class BlockItemPacketRewriter1_21 extends StructuredItemRewriter<Cl
         updateItemData(item);
 
         final StructuredDataContainer dataContainer = item.dataContainer();
-        if (dataContainer.contains(StructuredDataKey.RARITY)) {
+        if (dataContainer.has(StructuredDataKey.RARITY)) {
             return item;
         }
 
@@ -194,14 +193,14 @@ public final class BlockItemPacketRewriter1_21 extends StructuredItemRewriter<Cl
 
     public static void resetRarityValues(final Item item, final String tagName) {
         final StructuredDataContainer dataContainer = item.dataContainer();
-
+        final CompoundTag customData = dataContainer.get(StructuredDataKey.CUSTOM_DATA);
-        final StructuredData<CompoundTag> customData = dataContainer.getNonEmpty(StructuredDataKey.CUSTOM_DATA);
         if (customData == null) {
             return;
         }
-        if (customData.value().remove(tagName) != null) {
+
+        if (customData.remove(tagName) != null) {
             dataContainer.remove(StructuredDataKey.RARITY);
-            if (customData.value().isEmpty()) {
+            if (customData.isEmpty()) {
                 dataContainer.remove(StructuredDataKey.CUSTOM_DATA);
             }
         }

common/src/main/java/com/viaversion/viaversion/rewriter/StructuredItemRewriter.java

@@ -114,27 +114,27 @@ public class StructuredItemRewriter<C extends ClientboundPacketType, S extends S
         final MappingData mappingData = protocol.getMappingData();
         if (mappingData.getItemMappings() != null) {
             final Int2IntFunction itemIdRewriter = clientbound ? mappingData::getNewItemId : mappingData::getOldItemId;
-            container.updateIfPresent(StructuredDataKey.TRIM, value -> value.rewrite(itemIdRewriter));
+            container.replace(StructuredDataKey.TRIM, value -> value.rewrite(itemIdRewriter));
-            container.updateIfPresent(StructuredDataKey.POT_DECORATIONS, value -> value.rewrite(itemIdRewriter));
+            container.replace(StructuredDataKey.POT_DECORATIONS, value -> value.rewrite(itemIdRewriter));
         }
         if (mappingData.getBlockMappings() != null) {
             final Int2IntFunction blockIdRewriter = clientbound ? mappingData::getNewBlockId : mappingData::getOldBlockId;
-            container.updateIfPresent(StructuredDataKey.TOOL, value -> value.rewrite(blockIdRewriter));
+            container.replace(StructuredDataKey.TOOL, value -> value.rewrite(blockIdRewriter));
-            container.updateIfPresent(StructuredDataKey.CAN_PLACE_ON, value -> value.rewrite(blockIdRewriter));
+            container.replace(StructuredDataKey.CAN_PLACE_ON, value -> value.rewrite(blockIdRewriter));
-            container.updateIfPresent(StructuredDataKey.CAN_BREAK, value -> value.rewrite(blockIdRewriter));
+            container.replace(StructuredDataKey.CAN_BREAK, value -> value.rewrite(blockIdRewriter));
         }
         if (mappingData.getSoundMappings() != null) {
             final Int2IntFunction soundIdRewriter = clientbound ? mappingData::getNewSoundId : mappingData::getOldSoundId;
-            container.updateIfPresent(StructuredDataKey.INSTRUMENT, value -> value.isDirect() ? Holder.of(value.value().rewrite(soundIdRewriter)) : value);
+            container.replace(StructuredDataKey.INSTRUMENT, value -> value.isDirect() ? Holder.of(value.value().rewrite(soundIdRewriter)) : value);
-            container.updateIfPresent(StructuredDataKey.JUKEBOX_PLAYABLE, value -> value.rewrite(soundIdRewriter));
+            container.replace(StructuredDataKey.JUKEBOX_PLAYABLE, value -> value.rewrite(soundIdRewriter));
         }
         if (clientbound && protocol.getComponentRewriter() != null) {
             updateComponent(connection, item, StructuredDataKey.ITEM_NAME, "item_name");
             updateComponent(connection, item, StructuredDataKey.CUSTOM_NAME, "custom_name");
 
-            final StructuredData<Tag[]> loreData = container.getNonEmpty(StructuredDataKey.LORE);
+            final Tag[] lore = container.get(StructuredDataKey.LORE);
-            if (loreData != null) {
+            if (lore != null) {
-                for (final Tag tag : loreData.value()) {
+                for (final Tag tag : lore) {
                     protocol.getComponentRewriter().processTag(connection, tag);
                 }
             }
@@ -166,35 +166,35 @@ public class StructuredItemRewriter<C extends ClientboundPacketType, S extends S
     }
 
     protected void updateComponent(final UserConnection connection, final Item item, final StructuredDataKey<Tag> key, final String backupKey) {
-        final StructuredData<Tag> name = item.dataContainer().getNonEmpty(key);
+        final Tag name = item.dataContainer().get(key);
         if (name == null) {
             return;
         }
 
-        final Tag originalName = name.value().copy();
+        final Tag originalName = name.copy();
-        protocol.getComponentRewriter().processTag(connection, name.value());
+        protocol.getComponentRewriter().processTag(connection, name);
-        if (!name.value().equals(originalName)) {
+        if (!name.equals(originalName)) {
             saveTag(createCustomTag(item), originalName, backupKey);
         }
     }
 
     protected void restoreTextComponents(final Item item) {
         final StructuredDataContainer data = item.dataContainer();
-        final StructuredData<CompoundTag> customData = data.getNonEmpty(StructuredDataKey.CUSTOM_DATA);
+        final CompoundTag customData = data.get(StructuredDataKey.CUSTOM_DATA);
         if (customData == null) {
             return;
         }
 
         // Remove custom name
-        if (customData.value().remove(nbtTagName("added_custom_name")) != null) {
+        if (customData.remove(nbtTagName("added_custom_name")) != null) {
             data.remove(StructuredDataKey.CUSTOM_NAME);
         } else {
-            final Tag customName = removeBackupTag(customData.value(), "custom_name");
+            final Tag customName = removeBackupTag(customData, "custom_name");
             if (customName != null) {
                 data.set(StructuredDataKey.CUSTOM_NAME, customName);
             }
 
-            final Tag itemName = removeBackupTag(customData.value(), "item_name");
+            final Tag itemName = removeBackupTag(customData, "item_name");
             if (itemName != null) {
                 data.set(StructuredDataKey.ITEM_NAME, itemName);
             }
@@ -203,14 +203,12 @@ public class StructuredItemRewriter<C extends ClientboundPacketType, S extends S
 
     protected CompoundTag createCustomTag(final Item item) {
         final StructuredDataContainer data = item.dataContainer();
-        final StructuredData<CompoundTag> customData = data.getNonEmpty(StructuredDataKey.CUSTOM_DATA);
+        CompoundTag customData = data.get(StructuredDataKey.CUSTOM_DATA);
-        if (customData != null) {
+        if (customData == null) {
-            return customData.value();
+            customData = new CompoundTag();
+            data.set(StructuredDataKey.CUSTOM_DATA, customData);
         }
-
+        return customData;
-        final CompoundTag tag = new CompoundTag();
-        data.set(StructuredDataKey.CUSTOM_DATA, tag);
-        return tag;
     }
 
     protected void saveTag(final CompoundTag customData, final Tag tag, final String name) {