From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 16 Jul 2025 10:25:44 -0700
Subject: [PATCH] Fix spawners converted from 1.21.4 not running finalisation
 logic

DataConverter incorrectly placed a fall_distance value with 0.0
if the entity did not have a FallDistance entry. This results in the
entity spawn data having 2 entries, which prevents finalisation
logic from running.

We can fix this by removing the fall_distance entry if it is 0.0.

diff --git a/net/minecraft/world/level/SpawnData.java b/net/minecraft/world/level/SpawnData.java
index 60144561b277a2e20b50b8257b6d5e5c792629ce..04b4b7a50353497c3e637590fa2503379c304304 100644
--- a/net/minecraft/world/level/SpawnData.java
+++ b/net/minecraft/world/level/SpawnData.java
@@ -37,6 +37,13 @@ public record SpawnData(CompoundTag entityToSpawn, Optional<SpawnData.CustomSpaw
             entityToSpawn.remove("id");
         }
 
+        // Paper start - fix already converted data
+        // See https://github.com/PaperMC/DataConverter/commit/b6675e47ca068f152c3b648b3869fe63ca12b720
+        if (entityToSpawn.getDoubleOr("fall_distance", -1.0) == 0.0) {
+            entityToSpawn.remove("fall_distance");
+        }
+        // Paper end
+
         this.entityToSpawn = entityToSpawn;
         this.customSpawnRules = customSpawnRules;
         this.equipment = equipment;