Add FabricItemSettings and an API for custom item equipment slots (#956)

* Add FabricItemSettings and an API for custom item equipment slots

Closes #952.

* Bump module version

* Rename duck method to have fabric_ prefix and add Unique to mixin field

* Switch to FabricItemInternals + ExtraData like in FabricBlockSettings

fabric-item-api-v1/build.gradle

@@ -1,5 +1,5 @@
 archivesBaseName = "fabric-item-api-v1"
-version = getSubprojectVersion(project, "1.0.0")
+version = getSubprojectVersion(project, "1.1.0")
 
 dependencies {
 	compile project(path: ':fabric-api-base', configuration: 'dev')

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.item.v1;
+
+import net.minecraft.entity.EquipmentSlot;
+import net.minecraft.item.ItemStack;
+
+/**
+ * A provider for the preferred equipment slot of an item.
+ * This can be used to give non-armor items, such as blocks,
+ * an armor slot that they can go in.
+ *
+ * <p>Equipment slot providers can be set with {@link FabricItemSettings#equipmentSlot(EquipmentSlotProvider)}.
+ *
+ * <p>Note that items extending {@link net.minecraft.item.ArmorItem} don't need to use this
+ * as there's {@link net.minecraft.item.ArmorItem#getSlotType()}.
+ */
+@FunctionalInterface
+public interface EquipmentSlotProvider {
+	/**
+	 * Gets the preferred equipment slot for an item stack.
+	 *
+	 * <p>If there is no preferred armor equipment slot for the stack,
+	 * {@link EquipmentSlot#MAINHAND} can be returned.
+	 *
+	 * @param stack the item stack
+	 * @return the preferred equipment slot
+	 */
+	EquipmentSlot getPreferredEquipmentSlot(ItemStack stack);
+}

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

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.item.v1;
+
+import net.minecraft.item.FoodComponent;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemGroup;
+import net.minecraft.util.Rarity;
+
+import net.fabricmc.fabric.impl.item.FabricItemInternals;
+
+/**
+ * Fabric's version of Item.Settings. Adds additional methods and hooks
+ * not found in the original class.
+ *
+ * <p>To use it, simply replace {@code new Item.Settings()} with
+ * {@code new FabricItemSettings()}.
+ */
+public class FabricItemSettings extends Item.Settings {
+	/**
+	 * Sets the equipment slot provider of the item.
+	 *
+	 * @param equipmentSlotProvider the equipment slot provider
+	 * @return this builder
+	 */
+	public FabricItemSettings equipmentSlot(EquipmentSlotProvider equipmentSlotProvider) {
+		FabricItemInternals.computeExtraData(this).equipmentSlot(equipmentSlotProvider);
+		return this;
+	}
+
+	// Overrides of vanilla methods
+
+	@Override
+	public FabricItemSettings food(FoodComponent foodComponent) {
+		super.food(foodComponent);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings maxCount(int maxCount) {
+		super.maxCount(maxCount);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings maxDamageIfAbsent(int maxDamage) {
+		super.maxDamageIfAbsent(maxDamage);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings maxDamage(int maxDamage) {
+		super.maxDamage(maxDamage);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings recipeRemainder(Item recipeRemainder) {
+		super.recipeRemainder(recipeRemainder);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings group(ItemGroup group) {
+		super.group(group);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings rarity(Rarity rarity) {
+		super.rarity(rarity);
+		return this;
+	}
+
+	@Override
+	public FabricItemSettings fireproof() {
+		super.fireproof();
+		return this;
+	}
+}

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

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.impl.item;
+
+import java.util.WeakHashMap;
+
+import net.minecraft.item.Item;
+
+import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
+
+public final class FabricItemInternals {
+	private static final WeakHashMap<Item.Settings, ExtraData> extraData = new WeakHashMap<>();
+
+	private FabricItemInternals() {
+	}
+
+	public static ExtraData computeExtraData(Item.Settings settings) {
+		return extraData.computeIfAbsent(settings, s -> new ExtraData());
+	}
+
+	public static void onBuild(Item.Settings settings, Item item) {
+		ExtraData data = extraData.get(settings);
+
+		if (data != null) {
+			((ItemExtensions) item).fabric_setEquipmentSlotProvider(data.equipmentSlotProvider);
+		}
+	}
+
+	public static final class ExtraData {
+		private /* @Nullable */ EquipmentSlotProvider equipmentSlotProvider;
+
+		public void equipmentSlot(EquipmentSlotProvider equipmentSlotProvider) {
+			this.equipmentSlotProvider = equipmentSlotProvider;
+		}
+	}
+}

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

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.impl.item;
+
+import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
+
+public interface ItemExtensions {
+	EquipmentSlotProvider fabric_getEquipmentSlotProvider();
+	void fabric_setEquipmentSlotProvider(EquipmentSlotProvider equipmentSlotProvider);
+}

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/mixin/item/ItemMixin.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.mixin.item;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import net.minecraft.item.Item;
+
+import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
+import net.fabricmc.fabric.impl.item.FabricItemInternals;
+import net.fabricmc.fabric.impl.item.ItemExtensions;
+
+@Mixin(Item.class)
+abstract class ItemMixin implements ItemExtensions {
+	@Unique
+	private EquipmentSlotProvider equipmentSlotProvider;
+
+	@Inject(method = "<init>", at = @At("RETURN"))
+	private void onConstruct(Item.Settings settings, CallbackInfo info) {
+		FabricItemInternals.onBuild(settings, (Item) (Object) this);
+	}
+
+	@Override
+	public EquipmentSlotProvider fabric_getEquipmentSlotProvider() {
+		return equipmentSlotProvider;
+	}
+
+	@Override
+	public void fabric_setEquipmentSlotProvider(EquipmentSlotProvider equipmentSlotProvider) {
+		this.equipmentSlotProvider = equipmentSlotProvider;
+	}
+}

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/mixin/item/MobEntityMixin.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.mixin.item;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
+
+import net.minecraft.entity.EquipmentSlot;
+import net.minecraft.entity.mob.MobEntity;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+
+import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
+import net.fabricmc.fabric.impl.item.ItemExtensions;
+
+@Mixin(MobEntity.class)
+abstract class MobEntityMixin {
+	@Inject(method = "getPreferredEquipmentSlot", at = @At(value = "INVOKE_ASSIGN", target = "Lnet/minecraft/item/ItemStack;getItem()Lnet/minecraft/item/Item;"), cancellable = true, locals = LocalCapture.CAPTURE_FAILHARD)
+	private static void onGetPreferredEquipmentSlot(ItemStack stack, CallbackInfoReturnable<EquipmentSlot> info, Item item) {
+		EquipmentSlotProvider equipmentSlotProvider = ((ItemExtensions) item).fabric_getEquipmentSlotProvider();
+
+		if (equipmentSlotProvider != null) {
+			info.setReturnValue(equipmentSlotProvider.getPreferredEquipmentSlot(stack));
+		}
+	}
+}

fabric-item-api-v1/src/main/resources/fabric-item-api-v1.mixins.json

@@ -2,6 +2,10 @@
   "required": true,
   "package": "net.fabricmc.fabric.mixin.item",
   "compatibilityLevel": "JAVA_8",
+  "mixins": [
+    "ItemMixin",
+    "MobEntityMixin"
+  ],
   "client": [
     "client.ItemStackMixin"
   ],

fabric-item-api-v1/src/testmod/java/net/fabricmc/fabric/test/item/FabricItemSettingsTests.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.test.item;
+
+import net.minecraft.entity.EquipmentSlot;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemGroup;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.registry.Registry;
+
+import net.fabricmc.api.ModInitializer;
+import net.fabricmc.fabric.api.item.v1.FabricItemSettings;
+
+public class FabricItemSettingsTests implements ModInitializer {
+	@Override
+	public void onInitialize() {
+		// Registers an item with a custom equipment slot.
+		Item testItem = new Item(new FabricItemSettings().group(ItemGroup.MISC).equipmentSlot(stack -> EquipmentSlot.CHEST));
+		Registry.register(Registry.ITEM, new Identifier("fabric-item-api-v1-testmod", "test_item"), testItem);
+	}
+}

fabric-item-api-v1/src/testmod/resources/fabric.mod.json

@@ -9,6 +9,9 @@
     "fabric-item-api-v1": "*"
   },
   "entrypoints": {
+    "main": [
+      "net.fabricmc.fabric.test.item.FabricItemSettingsTests"
+    ],
     "client": [
       "net.fabricmc.fabric.test.item.client.TooltipTests"
     ]