Rework default field a bit

Loadable#field is now Loadable#requiredField to make it clear its a required field, will be going through usages and making sure all want required.
No longer override getAndDeserialize (now called getIfPresent) as that messes with some of the loadable builders (and notably cannot be built int). Plus, you might want to requrie a field that has its own default
Instead, going to encourage creation of custom defaultField impls without a default parameter for such usages
Loadable also now has a getOrDefault helper, same semantics as getIfPresent. Simplifies some field implementions

src/main/java/slimeknights/mantle/data/loadable/Loadable.java

@@ -11,14 +11,16 @@
 import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.EncoderException;
 import net.minecraft.network.FriendlyByteBuf;
+import org.jetbrains.annotations.Contract;
 import slimeknights.mantle.data.loadable.field.DefaultingField;
 import slimeknights.mantle.data.loadable.field.LoadableField;
-import slimeknights.mantle.data.loadable.field.NamedField;
 import slimeknights.mantle.data.loadable.field.NullableField;
+import slimeknights.mantle.data.loadable.field.RequiredField;
 import slimeknights.mantle.data.loadable.mapping.ListLoadable;
 import slimeknights.mantle.data.loadable.mapping.MappedLoadable;
 import slimeknights.mantle.data.loadable.mapping.SetLoadable;
 
+import javax.annotation.Nullable;
 import java.lang.reflect.Type;
 import java.util.List;
 import java.util.Set;
@@ -31,19 +33,6 @@ public interface Loadable<T> extends JsonDeserializer<T>, JsonSerializer<T> {
   /** Deserializes the object from json */
   T convert(JsonElement element, String key) throws JsonSyntaxException;
 
-  /**
-   * Gets then deserializes the given field
-   * @param parent  Parent to fetch field from
-   * @param key     Field to get
-   * @return  Value
-   */
-  default T getAndDeserialize(JsonObject parent, String key) {
-    if (parent.has(key)) {
-      return convert(parent.get(key), key);
-    }
-    throw new JsonSyntaxException("Missing JSON field " + key + "");
-  }
-
   /** Writes this object to json */
   JsonElement serialize(T object) throws RuntimeException;
 
@@ -67,11 +56,48 @@ default JsonElement serialize(T object, Type type, JsonSerializationContext cont
   }
 
 
+  /* Helpers for raw loadable use */
+
+  /**
+   * Gets then deserializes the given fieldm throwing if it is missing
+   * You should not override this method as we wish to leave that handling missing up to the RecordLoadable.
+   * Instead, consider a custom implementation of defaultField if you have a standard default.
+   * @param parent  Parent to fetch field from
+   * @param key     Field to get
+   * @return  Value, or throws if missing
+   */
+  default T getIfPresent(JsonObject parent, String key) {
+    if (parent.has(key)) {
+      return convert(parent.get(key), key);
+    }
+    throw new JsonSyntaxException("Missing JSON field " + key + "");
+  }
+
+  /**
+   * Gets then deserializes the given field, or returns a default value if its missing.
+   * You should not override this method as we wish to leave that handling missing up to the RecordLoadable.
+   * Instead, consider a custom implementation of defaultField if you have a standard default.
+   * @param parent        Parent to fetch field from
+   * @param key           Field to get
+   * @param defaultValue  Default value to fetch
+   * @return  Value or default.
+   */
+  @Nullable
+  @Contract("_,_,!null->!null")
+  default T getOrDefault(JsonObject parent, String key, @Nullable T defaultValue) {
+    JsonElement element = parent.get(key);
+    if (element != null && !element.isJsonNull()) {
+      return convert(element, key);
+    }
+    return defaultValue;
+  }
+
+
   /* Fields */
 
   /** Creates a required field from this loadable */
-  default <P> LoadableField<T,P> field(String key, Function<P,T> getter) {
-    return new NamedField<>(this, key, false, getter);
+  default <P> LoadableField<T,P> requiredField(String key, Function<P,T> getter) {
+    return new RequiredField<>(this, key, false, getter);
   }
 
   /** Creates an optional field that falls back to null */

src/main/java/slimeknights/mantle/data/loadable/common/BlockStateLoadable.java

@@ -65,7 +65,7 @@ private static <T extends Comparable<T>> BlockState setValue(BlockState state, P
 
   @Override
   public BlockState deserialize(JsonObject json) {
-    Block block = Loadables.BLOCK.getAndDeserialize(json, "block");
+    Block block = Loadables.BLOCK.getIfPresent(json, "block");
     BlockState state = block.defaultBlockState();
     if (json.has("properties")) {
       StateDefinition<Block,BlockState> definition = block.getStateDefinition();

src/main/java/slimeknights/mantle/data/loadable/common/FluidStackLoadable.java

@@ -39,7 +39,7 @@ private FluidStackLoadable() {}
   /** Field for an optional fluid */
   private static final LoadableField<Fluid,FluidStack> FLUID = Loadables.FLUID.defaultField("fluid", Fluids.EMPTY, false, FLUID_GETTER);
   /** Field for fluid stack count that allows empty */
-  private static final LoadableField<Integer,FluidStack> AMOUNT = IntLoadable.FROM_ZERO.field("amount", FluidStack::getAmount);
+  private static final LoadableField<Integer,FluidStack> AMOUNT = IntLoadable.FROM_ZERO.requiredField("amount", FluidStack::getAmount);
   /** Field for fluid stack count */
   private static final LoadableField<CompoundTag,FluidStack> NBT = NBTLoadable.ALLOW_STRING.nullableField("nbt", FluidStack::getTag);
 

src/main/java/slimeknights/mantle/data/loadable/common/IngredientLoadable.java

@@ -2,7 +2,6 @@
 
 import com.google.gson.JsonElement;
 import com.google.gson.JsonNull;
-import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.EncoderException;
@@ -15,14 +14,6 @@ public enum IngredientLoadable implements Loadable<Ingredient> {
   ALLOW_EMPTY,
   DISALLOW_EMPTY;
 
-  @Override
-  public Ingredient getAndDeserialize(JsonObject parent, String key) {
-    if (this == ALLOW_EMPTY && !parent.has(key)) {
-      return Ingredient.EMPTY;
-    }
-    return Loadable.super.getAndDeserialize(parent, key);
-  }
-
   @Override
   public Ingredient convert(JsonElement element, String key) throws JsonSyntaxException {
     Ingredient ingredient = Ingredient.fromJson(element);

src/main/java/slimeknights/mantle/data/loadable/common/NBTLoadable.java

@@ -78,11 +78,7 @@ private record NullableNBTField<P>(Loadable<CompoundTag> loadable, String key, F
     @Nullable
     @Override
     public CompoundTag get(JsonObject json) throws JsonSyntaxException {
-      JsonElement element = json.get(key);
-      if (element != null) {
-        return loadable.convert(element, key);
-      }
-      return null;
+      return loadable.getOrDefault(json, key, null);
     }
 
     @Override

src/main/java/slimeknights/mantle/data/loadable/field/DefaultingField.java

@@ -1,6 +1,5 @@
 package slimeknights.mantle.data.loadable.field;
 
-import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import slimeknights.mantle.data.loadable.Loadable;
@@ -15,13 +14,7 @@
 public record DefaultingField<T,P>(Loadable<T> loadable, String key, T defaultValue, boolean serializeDefault, Function<P,T> getter) implements AlwaysPresentLoadableField<T,P> {
   @Override
   public T get(JsonObject json) throws JsonSyntaxException {
-    if (json.has(key)) {
-      JsonElement element = json.get(key);
-      if (!element.isJsonNull()) {
-        return loadable.convert(element, key);
-      }
-    }
-    return defaultValue;
+    return loadable.getOrDefault(json, key, defaultValue);
   }
 
   @Override

src/main/java/slimeknights/mantle/data/loadable/field/NullableField.java

@@ -1,6 +1,5 @@
 package slimeknights.mantle.data.loadable.field;
 
-import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import net.minecraft.network.FriendlyByteBuf;
@@ -16,13 +15,7 @@
 public record NullableField<T,P>(Loadable<T> loadable, String key, Function<P,T> getter) implements LoadableField<T,P> {
   @Override
   public T get(JsonObject json) throws JsonSyntaxException {
-    if (json.has(key)) {
-      JsonElement element = json.get(key);
-      if (!element.isJsonNull()) {
-        return loadable.convert(element, key);
-      }
-    }
-    return null;
+    return loadable.getOrDefault(json, key, null);
   }
 
   @Override

src/main/java/slimeknights/mantle/data/loadable/field/NamedField.java → src/main/java/slimeknights/mantle/data/loadable/field/RequiredField.java

@@ -13,10 +13,10 @@
  * @param <P>  Parent object
  * @param <T>  Loadable type
  */
-public record NamedField<T,P>(Loadable<T> loadable, String key, boolean serializeNull, Function<P,T> getter) implements AlwaysPresentLoadableField<T,P> {
+public record RequiredField<T,P>(Loadable<T> loadable, String key, boolean serializeNull, Function<P,T> getter) implements AlwaysPresentLoadableField<T,P> {
   @Override
   public T get(JsonObject json) throws JsonSyntaxException {
-    return loadable.getAndDeserialize(json, key);
+    return loadable.getIfPresent(json, key);
   }
 
   @Override

src/main/java/slimeknights/mantle/data/loadable/mapping/CollectionLoadable.java

@@ -3,7 +3,6 @@
 import com.google.common.collect.ImmutableCollection;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
-import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import lombok.RequiredArgsConstructor;
 import net.minecraft.network.FriendlyByteBuf;
@@ -39,14 +38,6 @@ public C convert(JsonElement element, String key) throws JsonSyntaxException {
     return build(builder);
   }
 
-  @Override
-  public C getAndDeserialize(JsonObject parent, String key) {
-    if (minSize == 0 && !parent.has(key)) {
-      return build(makeBuilder());
-    }
-    return Loadable.super.getAndDeserialize(parent, key);
-  }
-
   @Override
   public JsonArray serialize(C collection) {
     JsonArray array = new JsonArray();

src/main/java/slimeknights/mantle/data/predicate/PredicateRegistry.java

@@ -27,8 +27,8 @@ public PredicateRegistry(String name, IJsonPredicate<T> defaultInstance) {
     // create common types
     Loadable<List<IJsonPredicate<T>>> list = this.list(2);
     invertedLoader = RecordLoadable.create(directField("inverted_type", p -> p.predicate), InvertedJsonPredicate::new);
-    andLoader = RecordLoadable.create(list.field("predicates", p -> p.children), AndJsonPredicate::new);
-    orLoader = RecordLoadable.create(list.field("predicates", p -> p.children), OrJsonPredicate::new);
+    andLoader = RecordLoadable.create(list.requiredField("predicates", p -> p.children), AndJsonPredicate::new);
+    orLoader = RecordLoadable.create(list.requiredField("predicates", p -> p.children), OrJsonPredicate::new);
     // register common types
     this.register(Mantle.getResource("any"), defaultInstance.getLoader());
     this.register(Mantle.getResource("inverted"), invertedLoader);

src/main/java/slimeknights/mantle/data/predicate/RegistryPredicateRegistry.java

@@ -32,8 +32,8 @@ public RegistryPredicateRegistry(String name, IJsonPredicate<T> defaultInstance,
     this.getter = getter;
     this.tagMatcher = tagMatcher;
     // create loaders
-    this.setLoader = RecordLoadable.create(registry.set().field(setKey, p -> p.set), SetPredicate::new);
-    this.tagLoader = RecordLoadable.create(tagKey.field("tag", p -> p.tag), TagPredicate::new);
+    this.setLoader = RecordLoadable.create(registry.set().requiredField(setKey, p -> p.set), SetPredicate::new);
+    this.tagLoader = RecordLoadable.create(tagKey.requiredField("tag", p -> p.tag), TagPredicate::new);
     // register loaders
     this.register(Mantle.getResource("set"), setLoader);
     this.register(Mantle.getResource("tag"), tagLoader);

src/main/java/slimeknights/mantle/data/predicate/block/BlockPropertiesPredicate.java

@@ -71,7 +71,7 @@ private static Property<?> parseProperty(Block block, String name, Function<Stri
   public static final RecordLoadable<BlockPropertiesPredicate> LOADER = new RecordLoadable<>() {
     @Override
     public BlockPropertiesPredicate deserialize(JsonObject json) {
-      Block block = Loadables.BLOCK.getAndDeserialize(json, "block");
+      Block block = Loadables.BLOCK.getIfPresent(json, "block");
       // TODO: this is a bit of a unique case for matcher, as its parsing from a map into a list, think about whether we can do something generic
       ImmutableList.Builder<Matcher> builder = ImmutableList.builder();
       for (Entry<String, JsonElement> entry : GsonHelper.getAsJsonObject(json, "properties").entrySet()) {

src/main/java/slimeknights/mantle/data/predicate/damage/SourceMessagePredicate.java

@@ -7,7 +7,7 @@
 
 /** Predicate that matches a named source */
 public record SourceMessagePredicate(String message) implements DamageSourcePredicate {
-  public static final RecordLoadable<SourceMessagePredicate> LOADER = RecordLoadable.create(StringLoadable.DEFAULT.field("message", SourceMessagePredicate::message), SourceMessagePredicate::new);
+  public static final RecordLoadable<SourceMessagePredicate> LOADER = RecordLoadable.create(StringLoadable.DEFAULT.requiredField("message", SourceMessagePredicate::message), SourceMessagePredicate::new);
 
   public SourceMessagePredicate(DamageSource source) {
     this(source.getMsgId());

src/main/java/slimeknights/mantle/data/predicate/entity/HasEnchantmentEntityPredicate.java

@@ -11,7 +11,7 @@
  * Predicate that checks if the given entity has the given enchantment on any of their equipment
  */
 public record HasEnchantmentEntityPredicate(Enchantment enchantment) implements LivingEntityPredicate {
-  public static final RecordLoadable<HasEnchantmentEntityPredicate> LOADER = RecordLoadable.create(Loadables.ENCHANTMENT.field("enchantment", HasEnchantmentEntityPredicate::enchantment), HasEnchantmentEntityPredicate::new);
+  public static final RecordLoadable<HasEnchantmentEntityPredicate> LOADER = RecordLoadable.create(Loadables.ENCHANTMENT.requiredField("enchantment", HasEnchantmentEntityPredicate::enchantment), HasEnchantmentEntityPredicate::new);
 
   @Override
   public boolean matches(LivingEntity entity) {

src/main/java/slimeknights/mantle/data/predicate/entity/MobTypePredicate.java

@@ -14,7 +14,7 @@ public record MobTypePredicate(MobType type) implements LivingEntityPredicate {
    */
   public static final NamedComponentRegistry<MobType> MOB_TYPES = new NamedComponentRegistry<>("Unknown mob type");
   /** Loader for a mob type predicate */
-  public static RecordLoadable<MobTypePredicate> LOADER = RecordLoadable.create(MOB_TYPES.field("mobs", MobTypePredicate::type), MobTypePredicate::new);
+  public static RecordLoadable<MobTypePredicate> LOADER = RecordLoadable.create(MOB_TYPES.requiredField("mobs", MobTypePredicate::type), MobTypePredicate::new);
 
   @Override
   public boolean matches(LivingEntity input) {

src/main/java/slimeknights/mantle/data/registry/GenericLoaderRegistry.java

@@ -65,7 +65,7 @@ public T convert(JsonElement element, String key) throws JsonSyntaxException {
     // first try object
     if (element.isJsonObject()) {
       JsonObject object = element.getAsJsonObject();
-      return loaders.getAndDeserialize(object, "type").deserialize(object);
+      return loaders.getIfPresent(object, "type").deserialize(object);
     }
     // try primitive if allowed
     if (compact && element.isJsonPrimitive()) {
@@ -85,14 +85,6 @@ public T deserialize(JsonElement element) {
     return convert(element, "[unknown]");
   }
 
-  @Override
-  public T getAndDeserialize(JsonObject parent, String key) {
-    if (defaultInstance != null && !parent.has(key)) {
-      return defaultInstance;
-    }
-    return Loadable.super.getAndDeserialize(parent, key);
-  }
-
   /** Serializes the object to json, fighting generics */
   @SuppressWarnings("unchecked")
   private <L extends IHaveLoader> JsonElement serialize(IGenericLoader<L> loader, T src) {
@@ -177,6 +169,11 @@ public <P> LoadableField<T,P> defaultField(String key, boolean serializeDefault,
     throw new IllegalStateException(name + " registry has no default instance, cannot make a default field");
   }
 
+  /** Creates a defaulting field that does not serialize */
+  public <P> LoadableField<T,P> defaultField(String key, Function<P,T> getter) {
+    return defaultField(key, false, getter);
+  }
+
   /** Creates a field that loads this object directly into the parent JSON object */
   public <P> LoadableField<T,P> directField(String typeKey, Function<P,T> getter) {
     return new DirectRegistryField<>(this, typeKey, getter);

src/main/java/slimeknights/mantle/recipe/helper/ItemOutput.java

@@ -2,13 +2,11 @@
 
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
-import com.google.gson.JsonPrimitive;
 import com.google.gson.JsonSyntaxException;
 import com.mojang.serialization.Codec;
 import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.EncoderException;
 import lombok.RequiredArgsConstructor;
-import net.minecraft.core.Registry;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.tags.TagKey;
 import net.minecraft.util.GsonHelper;
@@ -17,8 +15,9 @@
 import net.minecraft.world.level.ItemLike;
 import slimeknights.mantle.data.JsonCodec;
 import slimeknights.mantle.data.loadable.Loadable;
+import slimeknights.mantle.data.loadable.Loadables;
 import slimeknights.mantle.data.loadable.common.ItemStackLoadable;
-import slimeknights.mantle.util.JsonHelper;
+import slimeknights.mantle.data.loadable.primitive.IntLoadable;
 
 import java.util.function.Supplier;
 
@@ -43,7 +42,7 @@ public String toString() {
       return "ItemOutput";
     }
   };
-  /** Loadable instance for an item output. Custom to handle the eithering behavior */
+  /** Loadable instance for an item output. Not using EitherLoadable as we just always sync items to keep thing simplier. */
   public static Loadable<ItemOutput> LOADABLE = new Loadable<>() {
     @Override
     public ItemOutput convert(JsonElement element, String key) throws JsonSyntaxException {
@@ -132,13 +131,13 @@ public static ItemOutput fromJson(JsonElement element) {
     // if it has a tag, parse as tag
     JsonObject json = element.getAsJsonObject();
     if (json.has("tag")) {
-      TagKey<Item> tag = TagKey.create(Registry.ITEM_REGISTRY, JsonHelper.getResourceLocation(json, "tag"));
-      int count = GsonHelper.getAsInt(json, "count", 1);
+      TagKey<Item> tag = Loadables.ITEM_TAG.getIfPresent(json, "tag");
+      int count = IntLoadable.FROM_ONE.getOrDefault(json, "count", 1);
       return fromTag(tag, count);
     }
 
     // default: parse as item stack using loadables
-    return fromStack(ItemStackLoadable.REQUIRED_STACK_NBT.convert(json, "item"));
+    return fromStack(ItemStackLoadable.REQUIRED_STACK_NBT.deserialize(json));
   }
 
   /**
@@ -175,14 +174,14 @@ public ItemStack get() {
 
     @Override
     public JsonElement serialize() {
-      String itemName = Registry.ITEM.getKey(item).toString();
+      JsonElement item = Loadables.ITEM.serialize(this.item);
       if (count > 1) {
         JsonObject json = new JsonObject();
-        json.addProperty("item", itemName);
+        json.add("item", item);
         json.addProperty("count", count);
         return json;
       } else {
-        return new JsonPrimitive(itemName);
+        return item;
       }
     }
   }