From 01aa235fff8edfed8923de7dcb3eb9208d0e00ec Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Mon, 24 Feb 2025 17:23:30 -0700
Subject: [PATCH] Clear lastSection on game event listener removal (fixes #87)

---
 .../DynamicGameEventListenerMixin.java        | 25 +++++++++++++++++++
 src/main/resources/moonrise.mixins.json       |  1 +
 2 files changed, 26 insertions(+)
 create mode 100644 src/main/java/ca/spottedleaf/moonrise/mixin/chunk_system/DynamicGameEventListenerMixin.java

diff --git a/src/main/java/ca/spottedleaf/moonrise/mixin/chunk_system/DynamicGameEventListenerMixin.java b/src/main/java/ca/spottedleaf/moonrise/mixin/chunk_system/DynamicGameEventListenerMixin.java
new file mode 100644
index 00000000..ed0c3baa
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/moonrise/mixin/chunk_system/DynamicGameEventListenerMixin.java
@@ -0,0 +1,25 @@
+package ca.spottedleaf.moonrise.mixin.chunk_system;
+
+import net.minecraft.core.SectionPos;
+import net.minecraft.world.level.gameevent.DynamicGameEventListener;
+import org.jetbrains.annotations.Nullable;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(DynamicGameEventListener.class)
+abstract class DynamicGameEventListenerMixin {
+    @Shadow @Nullable private SectionPos lastSection;
+
+    @Inject(method = "remove", at = @At("RETURN"))
+    private void onRemove(final CallbackInfo ci) {
+        // We need to unset the last section when removed, otherwise if the same instance is re-added at the same position it
+        // will assume there was no change and fail to re-register.
+        // In vanilla, chunks rarely unload and re-load quickly enough to trigger this issue. However, our chunk system has a
+        // quirk where fast chunk reload cycles will often occur on player login (see PR #22).
+        // So we fix this vanilla oversight as our changes cause it to manifest in bugs much more often (see issue #87).
+        this.lastSection = null;
+    }
+}
diff --git a/src/main/resources/moonrise.mixins.json b/src/main/resources/moonrise.mixins.json
index 76f5f54b..bb7be208 100644
--- a/src/main/resources/moonrise.mixins.json
+++ b/src/main/resources/moonrise.mixins.json
@@ -26,6 +26,7 @@
         "chunk_system.ChunkStepMixin",
         "chunk_system.ChunkStorageMixin",
         "chunk_system.DistanceManagerMixin",
+        "chunk_system.DynamicGameEventListenerMixin",
         "chunk_system.EntityGetterMixin",
         "chunk_system.EntityMixin",
         "chunk_system.EntityTickListMixin",