Copy stack when component changes

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

@@ -16,6 +16,8 @@
 
 package net.fabricmc.fabric.impl.transfer.item;
 
+import java.util.Objects;
+
 import net.minecraft.block.ChestBlock;
 import net.minecraft.block.entity.AbstractFurnaceBlockEntity;
 import net.minecraft.block.entity.BrewingStandBlockEntity;
@@ -153,9 +155,14 @@ protected void onFinalCommit() {
 		}
 
 		if (!original.isEmpty() && original.getItem() == currentStack.getItem()) {
-			// None is empty and the items match: just update the amount and NBT, and reuse the original stack.
+			// Components have changed, we need to copy the stack.
+			if (!Objects.equals(original.getComponentChanges(), currentStack.getComponentChanges())) {
+				setStack(currentStack.copy());
+				return;
+			}
+
+			// None is empty and the items and components match: just update the amount, and reuse the original stack.
 			original.setCount(currentStack.getCount());
-			original.copyComponentsFrom(currentStack.getComponents());
 			setStack(original);
 		} else {
 			// Otherwise assume everything was taken from original so empty it.

fabric-transfer-api-v1/src/test/java/net/fabricmc/fabric/test/transfer/unittests/ItemTests.java

@@ -84,7 +84,8 @@ public void testStackReference() {
 
 		if (stack != inv.getStack(0)) throw new AssertionError("Stack should have stayed the same.");
 
-		// Also edit the stack when the item matches, even when the NBT and the count change.
+		// Also edit the stack when the item matches, even when the components and the count change.
+		// We expect the stack to change
 		ItemVariant oldVariant = ItemVariant.of(Items.DIAMOND);
 		ComponentChanges components = ComponentChanges.builder().add(ENERGY, 42).build();
 		ItemVariant newVariant = ItemVariant.of(Items.DIAMOND, components);
@@ -95,7 +96,8 @@ public void testStackReference() {
 			tx.commit();
 		}
 
-		if (stack != inv.getStack(0)) throw new AssertionError("Stack should have stayed the same.");
+		if (stack == inv.getStack(0)) throw new AssertionError("Stack should have changed");
+		stack = inv.getStack(0);
 		if (!stackEquals(stack, newVariant, 5)) throw new AssertionError("Failed to update stack NBT or count.");
 	}