Fix max health not being restored in some scenarios.

This is a backport of the fixes from 1.20.4 for #7 and #5. It also
contains the fix for some modded attribute sources being applied
too late in the load cycle.

Common/src/main/java/net/darkhax/maxhealthfix/IHealthFixable.java

@@ -0,0 +1,6 @@
+package net.darkhax.maxhealthfix;
+
+public interface IHealthFixable {
+
+    void maxhealthfix$setRestorePoint(float restorePoint);
+}

Common/src/main/java/net/darkhax/maxhealthfix/mixin/MixinLivingEntity.java

@@ -1,5 +1,6 @@
 package net.darkhax.maxhealthfix.mixin;
 
+import net.darkhax.maxhealthfix.IHealthFixable;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.Tag;
 import net.minecraft.world.entity.LivingEntity;
@@ -12,25 +13,21 @@
 
 import javax.annotation.Nullable;
 
-@Mixin(LivingEntity.class)
-public abstract class MixinLivingEntity {
+@Mixin(value = LivingEntity.class, priority = 9001)
+public abstract class MixinLivingEntity implements IHealthFixable {
 
     /**
-     * This float is used to temporarily hold the actual health of the entity while the entity data is being
-     * deserialized. A null value is used to indicate that the health does not need correcting.
+     * Temporarily holds the original health value of the entity.
      */
     @Unique
     @Nullable
     private Float actualHealth = null;
 
     /**
-     * The vanilla code will reset the entity health when the deserialized value exceeds {@link
-     * LivingEntity#getMaxHealth()}. This generally is not an issue, however when entities are initially loaded their
-     * max health attribute has not been properly initialized. This is the source of MC-17876.
-     * <p>
-     * This mixin is used to circumvent this faulty logic by capturing the deserialized value early and storing it in
-     * {@link #actualHealth}. This approach is favoured over attempting to initialize attributes early as there is no
-     * standard way to do this that would reasonably account for modded attribute sources.
+     * The vanilla code loads entity health before attributes and equipment have been loaded in. This leads to players
+     * with health over the default maximum being reset when they join the game. This is the source of MC-17876. This
+     * mixin attempts to solve this issue by capturing the health value before it is applied and applying it again at a
+     * later point.
      */
     @Inject(method = "readAdditionalSaveData(Lnet/minecraft/nbt/CompoundTag;)V", at = @At("HEAD"))
     private void maxhealthfix$readAdditionalSaveData(CompoundTag tag, CallbackInfo callback) {
@@ -47,13 +44,11 @@ public abstract class MixinLivingEntity {
     }
 
     /**
-     * This mixin is used to apply the {@link #actualHealth} value after entity equipment has been deserialized and
-     * properly applied to the entity. This approach is favoured over directly setting the health during deserialization
-     * as it has less potential for de-syncs. An example scenario of concern would be a player saving their game and
-     * removing a mod that added the attribute, resulting in too much health.
+     * This mixin is used to apply the {@link #actualHealth} at the end of the first tick. This is done to give
+     * equipment and modded mechanics like baubles/curios a chance to load in.
      */
-    @Inject(method = "detectEquipmentUpdates()V", at = @At("RETURN"))
-    private void maxhealthfix$detectEquipmentUpdates(CallbackInfo callback) {
+    @Inject(method = "tick()V", at = @At("TAIL"))
+    private void maxhealthfix$tick(CallbackInfo callback) {
 
         if (actualHealth != null) {
 
@@ -66,6 +61,12 @@ public abstract class MixinLivingEntity {
         }
     }
 
+    @Override
+    public void maxhealthfix$setRestorePoint(float restorePoint) {
+
+        this.actualHealth = restorePoint;
+    }
+
     @Shadow
     public abstract float getMaxHealth();
 

Common/src/main/java/net/darkhax/maxhealthfix/mixin/MixinPlayerList.java

@@ -0,0 +1,28 @@
+package net.darkhax.maxhealthfix.mixin;
+
+import net.darkhax.maxhealthfix.IHealthFixable;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.players.PlayerList;
+import net.minecraft.world.phys.Vec3;
+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 java.util.Optional;
+
+@Mixin(PlayerList.class)
+public class MixinPlayerList {
+
+    @Inject(method = "respawn(Lnet/minecraft/server/level/ServerPlayer;Z)Lnet/minecraft/server/level/ServerPlayer;", at = @At(value = "INVOKE", target = "Lnet/minecraft/server/level/ServerPlayer;setHealth(F)V"), locals = LocalCapture.CAPTURE_FAILSOFT)
+    private void onPlayerRespawn(ServerPlayer oldPlayer, boolean fromEnd, CallbackInfoReturnable<ServerPlayer> cbi, BlockPos respawnPos, float respawnAngle, boolean wasForced, ServerLevel oldDimension, Optional<Vec3> calculatedPos, ServerLevel overworld, ServerPlayer newPlayer) {
+
+        if (newPlayer instanceof IHealthFixable fixable) {
+
+            fixable.maxhealthfix$setRestorePoint(oldPlayer.getMaxHealth());
+        }
+    }
+}

Common/src/main/resources/maxhealthfix.common.mixins.json

@@ -4,7 +4,8 @@
   "package": "net.darkhax.maxhealthfix.mixin",
   "compatibilityLevel": "JAVA_17",
   "mixins": [
-    "MixinLivingEntity"
+    "MixinLivingEntity",
+    "MixinPlayerList"
   ],
   "injectors": {
     "defaultRequire": 1