Adds knockback attribute to players and updated knockback calculation to PlayerEntity#attack (#7806)

patches/minecraft/net/minecraft/entity/player/PlayerEntity.java.patch

@@ -23,7 +23,7 @@
  
     public static AttributeModifierMap.MutableAttribute func_234570_el_() {
 -      return LivingEntity.func_233639_cI_().func_233815_a_(Attributes.field_233823_f_, 1.0D).func_233815_a_(Attributes.field_233821_d_, (double)0.1F).func_233814_a_(Attributes.field_233825_h_).func_233814_a_(Attributes.field_233828_k_);
-+      return LivingEntity.func_233639_cI_().func_233815_a_(Attributes.field_233823_f_, 1.0D).func_233815_a_(Attributes.field_233821_d_, (double)0.1F).func_233814_a_(Attributes.field_233825_h_).func_233814_a_(Attributes.field_233828_k_).func_233814_a_(net.minecraftforge.common.ForgeMod.REACH_DISTANCE.get());
++      return LivingEntity.func_233639_cI_().func_233815_a_(Attributes.field_233823_f_, 1.0D).func_233815_a_(Attributes.field_233821_d_, (double)0.1F).func_233814_a_(Attributes.field_233825_h_).func_233814_a_(Attributes.field_233828_k_).func_233814_a_(net.minecraftforge.common.ForgeMod.REACH_DISTANCE.get()).func_233814_a_(Attributes.field_233824_g_);
     }
  
     protected void func_70088_a() {
@@ -198,6 +198,15 @@
        if (p_71059_1_.func_70075_an()) {
           if (!p_71059_1_.func_85031_j(this)) {
              float f = (float)this.func_233637_b_(Attributes.field_233823_f_);
+@@ -1028,7 +_,7 @@
+             if (f > 0.0F || f1 > 0.0F) {
+                boolean flag = f2 > 0.9F;
+                boolean flag1 = false;
+-               int i = 0;
++               float i = (float)this.func_233637_b_(Attributes.field_233824_g_); // Forge: Initialize this value to the attack knockback attribute of the player, which is by default 0
+                i = i + EnchantmentHelper.func_77501_a(this);
+                if (this.func_70051_ag() && flag) {
+                   this.field_70170_p.func_184148_a((PlayerEntity)null, this.func_226277_ct_(), this.func_226278_cu_(), this.func_226281_cx_(), SoundEvents.field_187721_dT, this.func_184176_by(), 1.0F, 1.0F);
 @@ -1038,8 +_,10 @@
  
                 boolean flag2 = flag && this.field_70143_R > 0.0F && !this.field_70122_E && !this.func_70617_f_() && !this.func_70090_H() && !this.func_70644_a(Effects.field_76440_q) && !this.func_184218_aH() && p_71059_1_ instanceof LivingEntity;

src/test/java/net/minecraftforge/debug/entity/player/PlayerAttackKnockbackTest.java

@@ -0,0 +1,67 @@
+package net.minecraftforge.debug.entity.player;
+
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.Multimap;
+import net.minecraft.entity.ai.attributes.Attribute;
+import net.minecraft.entity.ai.attributes.AttributeModifier;
+import net.minecraft.entity.ai.attributes.Attributes;
+import net.minecraft.inventory.EquipmentSlotType;
+import net.minecraft.item.*;
+import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.fml.RegistryObject;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
+import net.minecraftforge.registries.DeferredRegister;
+import net.minecraftforge.registries.ForgeRegistries;
+
+import java.util.UUID;
+
+/**
+ * Tests if the patch to PlayerEntity to make it utilize Attributes.ATTACK_KNOCKBACK works
+ * The Knockback Sword adds a modifier to the user's attack knockback
+ * The goal of this patch is to allow modders to more easily add equipment or potion effects that affect the attack knockback of players
+ * As well as allow command users to modify this attribute for a player
+ */
+@Mod(PlayerAttackKnockbackTest.MODID)
+public class PlayerAttackKnockbackTest {
+
+    static final String MODID = "player_attack_knockback_test";
+
+    static final float ATTACK_KNOCKBACK_VALUE = 2.0F; // Change this value for testing, but note that the attribute is capped at 5.0D
+
+    static final DeferredRegister<Item> ITEMS = DeferredRegister.create(ForgeRegistries.ITEMS, MODID);
+
+    static RegistryObject<Item> KNOCKBACK_SWORD = ITEMS.register("knockback_sword", () ->
+            new KnockbackSwordItem(ItemTier.IRON, 3, -2.4F, ATTACK_KNOCKBACK_VALUE, (new Item.Properties()).tab(ItemGroup.TAB_COMBAT))
+    );
+
+    public PlayerAttackKnockbackTest()
+    {
+        IEventBus modEventBus = FMLJavaModLoadingContext.get().getModEventBus();
+        ITEMS.register(modEventBus);
+    }
+
+    static class KnockbackSwordItem extends SwordItem{
+        private final float attackKnockback;
+        private final Multimap<Attribute, AttributeModifier> defaultModifiers = ArrayListMultimap.create(); // initialize as empty
+        protected static final UUID BASE_ATTACK_KNOCKBACK_UUID = UUID.fromString("01efce91-ab3a-4163-b464-5c7bd1ae5496");
+
+        KnockbackSwordItem(IItemTier itemTier, int attackDamageIn, float attackSpeedIn, float attackKnockbackIn, Properties properties) {
+            super(itemTier, attackDamageIn, attackSpeedIn, properties);
+            this.attackKnockback = attackKnockbackIn;
+        }
+
+        @Override
+        public Multimap<Attribute, AttributeModifier> getDefaultAttributeModifiers(EquipmentSlotType equipmentSlotType) {
+            if(equipmentSlotType == EquipmentSlotType.MAINHAND){
+                if(this.defaultModifiers.isEmpty()){
+                    Multimap<Attribute, AttributeModifier> oldAttributeModifiers = super.getDefaultAttributeModifiers(equipmentSlotType);
+                    this.defaultModifiers.putAll(oldAttributeModifiers);
+                    this.defaultModifiers.put(Attributes.ATTACK_KNOCKBACK, new AttributeModifier(BASE_ATTACK_KNOCKBACK_UUID, "Weapon modifier", (double)this.attackKnockback, AttributeModifier.Operation.ADDITION));
+                }
+                return this.defaultModifiers;
+            }
+            else return super.getDefaultAttributeModifiers(equipmentSlotType);
+        }
+    }
+}

src/test/resources/META-INF/mods.toml

@@ -125,4 +125,6 @@ license="LGPL v2.1"
 [[mods]]
     modId="text_linear_filtering_test"
 [[mods]]
-    modId="custom_tas_test"
+    modId="player_attack_knockback_test"
+[[mods]]
+    modId="custom_tas_test"

src/test/resources/assets/player_attack_knockback_test/lang/en_us.json

@@ -0,0 +1,3 @@
+{
+  "item.player_attack_knockback_test.knockback_sword": "Knockback Sword"
+}

src/test/resources/assets/player_attack_knockback_test/models/item/knockback_sword.json

@@ -0,0 +1,6 @@
+{
+  "parent": "minecraft:item/handheld",
+  "textures": {
+    "layer0": "player_attack_knockback_test:item/knockback_sword"
+  }
+}