Make SlottedStorage#getSlots return a view, remove useless field, add…

… UnmodifiableView annotations

fabric-transfer-api-v1/src/main/java/net/fabricmc/fabric/api/transfer/v1/context/ContainerItemContext.java

@@ -20,6 +20,7 @@
 
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.UnmodifiableView;
 
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.player.PlayerInventory;
@@ -293,5 +294,6 @@ default long exchange(ItemVariant newVariant, long maxAmount, TransactionContext
 	 *
 	 * @return An unmodifiable list containing additional slots of this context. If no additional slot is available, the list is empty.
 	 */
+	@UnmodifiableView
 	List<SingleSlotStorage<ItemVariant>> getAdditionalSlots();
 }

fabric-transfer-api-v1/src/main/java/net/fabricmc/fabric/api/transfer/v1/item/InventoryStorage.java

@@ -21,6 +21,7 @@
 
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.UnmodifiableView;
 
 import net.minecraft.entity.player.PlayerInventory;
 import net.minecraft.inventory.Inventory;
@@ -70,6 +71,7 @@ static InventoryStorage of(Inventory inventory, @Nullable Direction direction) {
 	 * Each wrapper corresponds to a single slot in the inventory.
 	 */
 	@Override
+	@UnmodifiableView
 	List<SingleSlotStorage<ItemVariant>> getSlots();
 
 	/**

fabric-transfer-api-v1/src/main/java/net/fabricmc/fabric/api/transfer/v1/storage/SlottedStorage.java

@@ -19,8 +19,11 @@
 import java.util.List;
 
 import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.UnmodifiableView;
 
 import net.fabricmc.fabric.api.transfer.v1.storage.base.SingleSlotStorage;
+import net.fabricmc.fabric.api.transfer.v1.context.ContainerItemContext;
+import net.fabricmc.fabric.impl.transfer.TransferApiImpl;
 
 /**
  * A {@link Storage} implementation made of indexed slots.
@@ -49,16 +52,16 @@ public interface SlottedStorage<T> extends Storage<T> {
 	SingleSlotStorage<T> getSlot(int slot);
 
 	/**
-	 * Retrieve all the slots of this storage. <b>The list must not be modified.</b>
+	 * Retrieve a list containing all the slots of this storage. <b>The list must not be modified.</b>
+	 *
+	 * <p>This function can be used to interface with code that requires a slot list,
+	 * for example {@link StorageUtil#insertStacking} or {@link ContainerItemContext#getAdditionalSlots()}.
+	 *
+	 * <p>It is guaranteed that calling this function is fast.
+	 * The default implementation returns a view over the storage that delegates to {@link #getSlotCount} and {@link #getSlot}.
 	 */
+	@UnmodifiableView
 	default List<SingleSlotStorage<T>> getSlots() {
-		int slotCount = getSlotCount();
-		SingleSlotStorage<T>[] slots = new SingleSlotStorage[slotCount];
-
-		for (int i = 0; i < slotCount; i++) {
-			slots[i] = getSlot(i);
-		}
-
-		return List.of(slots);
+		return TransferApiImpl.makeListView(this);
 	}
 }

fabric-transfer-api-v1/src/main/java/net/fabricmc/fabric/impl/transfer/TransferApiImpl.java

@@ -16,16 +16,20 @@
 
 package net.fabricmc.fabric.impl.transfer;
 
+import java.util.AbstractList;
 import java.util.Collections;
 import java.util.Iterator;
+import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.slf4j.LoggerFactory;
 import org.slf4j.Logger;
 
+import net.fabricmc.fabric.api.transfer.v1.storage.SlottedStorage;
 import net.fabricmc.fabric.api.transfer.v1.storage.Storage;
 import net.fabricmc.fabric.api.transfer.v1.storage.StorageView;
+import net.fabricmc.fabric.api.transfer.v1.storage.base.SingleSlotStorage;
 import net.fabricmc.fabric.api.transfer.v1.transaction.TransactionContext;
 
 public class TransferApiImpl {
@@ -64,11 +68,6 @@ public long getVersion() {
 		}
 	};
 
-	/**
-	 * Not null when writing to an inventory in a transaction, null otherwise.
-	 */
-	public static final ThreadLocal<Object> SUPPRESS_SPECIAL_LOGIC = new ThreadLocal<>();
-
 	public static <T> Iterator<T> singletonIterator(T it) {
 		return new Iterator<T>() {
 			boolean hasNext = true;
@@ -125,4 +124,18 @@ public StorageView<T> next() {
 			}
 		};
 	}
+
+	public static <T> List<SingleSlotStorage<T>> makeListView(SlottedStorage<T> storage) {
+		return new AbstractList<>() {
+			@Override
+			public SingleSlotStorage<T> get(int index) {
+				return storage.getSlot(index);
+			}
+
+			@Override
+			public int size() {
+				return storage.getSlotCount();
+			}
+		};
+	}
 }